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Groups > linux.kernel > #1668353 > unrolled thread
| Started by | Mauro Carvalho Chehab <mchehab@s-opensource.com> |
|---|---|
| First post | 2017-06-17 17:50 +0200 |
| Last post | 2017-06-19 21:00 +0200 |
| Articles | 6 — 2 participants |
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[PATCH v2 01/31] bcache.txt: standardize document format Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2017-06-17 17:50 +0200
[PATCH v2 13/31] DMA-API.txt: standardize document format Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2017-06-17 17:50 +0200
[PATCH v2 16/31] DMA-ISA-LPC.txt: standardize document format Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2017-06-17 17:50 +0200
[PATCH v2 09/31] cputopology.txt: standardize document format Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2017-06-17 17:50 +0200
[PATCH v2 22/31] gcc-plugins.txt: standardize document format Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2017-06-17 17:50 +0200
Re: [PATCH v2 22/31] gcc-plugins.txt: standardize document format Kees Cook <keescook@chromium.org> - 2017-06-19 21:00 +0200
| From | Mauro Carvalho Chehab <mchehab@s-opensource.com> |
|---|---|
| Date | 2017-06-17 17:50 +0200 |
| Subject | [PATCH v2 01/31] bcache.txt: standardize document format |
| Message-ID | <tTnPH-y3-7@gated-at.bofh.it> |
Each text file under Documentation follows a different
format. Some doesn't even have titles!
Change its representation to follow the adopted standard,
using ReST markups for it to be parseable by Sphinx:
- Add a title for the document;
- Use a list for the listed URLs;
- mark literal blocks;
- adjust whitespaces;
- Don't capitalize section titles.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
---
Documentation/bcache.txt | 200 ++++++++++++++++++++++++++---------------------
1 file changed, 112 insertions(+), 88 deletions(-)
diff --git a/Documentation/bcache.txt b/Documentation/bcache.txt
index a9259b562d5c..c0ce64d75bbf 100644
--- a/Documentation/bcache.txt
+++ b/Documentation/bcache.txt
@@ -1,10 +1,15 @@
+============================
+A block layer cache (bcache)
+============================
+
Say you've got a big slow raid 6, and an ssd or three. Wouldn't it be
nice if you could use them as cache... Hence bcache.
Wiki and git repositories are at:
- http://bcache.evilpiepirate.org
- http://evilpiepirate.org/git/linux-bcache.git
- http://evilpiepirate.org/git/bcache-tools.git
+
+ - http://bcache.evilpiepirate.org
+ - http://evilpiepirate.org/git/linux-bcache.git
+ - http://evilpiepirate.org/git/bcache-tools.git
It's designed around the performance characteristics of SSDs - it only allocates
in erase block sized buckets, and it uses a hybrid btree/log to track cached
@@ -37,17 +42,19 @@ to be flushed.
Getting started:
You'll need make-bcache from the bcache-tools repository. Both the cache device
-and backing device must be formatted before use.
+and backing device must be formatted before use::
+
make-bcache -B /dev/sdb
make-bcache -C /dev/sdc
make-bcache has the ability to format multiple devices at the same time - if
you format your backing devices and cache device at the same time, you won't
-have to manually attach:
+have to manually attach::
+
make-bcache -B /dev/sda /dev/sdb -C /dev/sdc
bcache-tools now ships udev rules, and bcache devices are known to the kernel
-immediately. Without udev, you can manually register devices like this:
+immediately. Without udev, you can manually register devices like this::
echo /dev/sdb > /sys/fs/bcache/register
echo /dev/sdc > /sys/fs/bcache/register
@@ -60,16 +67,16 @@ slow devices as bcache backing devices without a cache, and you can choose to ad
a caching device later.
See 'ATTACHING' section below.
-The devices show up as:
+The devices show up as::
/dev/bcache<N>
-As well as (with udev):
+As well as (with udev)::
/dev/bcache/by-uuid/<uuid>
/dev/bcache/by-label/<label>
-To get started:
+To get started::
mkfs.ext4 /dev/bcache0
mount /dev/bcache0 /mnt
@@ -81,13 +88,13 @@ Cache devices are managed as sets; multiple caches per set isn't supported yet
but will allow for mirroring of metadata and dirty data in the future. Your new
cache set shows up as /sys/fs/bcache/<UUID>
-ATTACHING
+Attaching
---------
After your cache device and backing device are registered, the backing device
must be attached to your cache set to enable caching. Attaching a backing
device to a cache set is done thusly, with the UUID of the cache set in
-/sys/fs/bcache:
+/sys/fs/bcache::
echo <CSET-UUID> > /sys/block/bcache0/bcache/attach
@@ -97,7 +104,7 @@ your bcache devices. If a backing device has data in a cache somewhere, the
important if you have writeback caching turned on.
If you're booting up and your cache device is gone and never coming back, you
-can force run the backing device:
+can force run the backing device::
echo 1 > /sys/block/sdb/bcache/running
@@ -110,7 +117,7 @@ but all the cached data will be invalidated. If there was dirty data in the
cache, don't expect the filesystem to be recoverable - you will have massive
filesystem corruption, though ext4's fsck does work miracles.
-ERROR HANDLING
+Error Handling
--------------
Bcache tries to transparently handle IO errors to/from the cache device without
@@ -134,25 +141,27 @@ the backing devices to passthrough mode.
read some of the dirty data, though.
-HOWTO/COOKBOOK
+Howto/cookbook
--------------
A) Starting a bcache with a missing caching device
If registering the backing device doesn't help, it's already there, you just need
-to force it to run without the cache:
+to force it to run without the cache::
+
host:~# echo /dev/sdb1 > /sys/fs/bcache/register
[ 119.844831] bcache: register_bcache() error opening /dev/sdb1: device already registered
Next, you try to register your caching device if it's present. However
if it's absent, or registration fails for some reason, you can still
-start your bcache without its cache, like so:
+start your bcache without its cache, like so::
+
host:/sys/block/sdb/sdb1/bcache# echo 1 > running
Note that this may cause data loss if you were running in writeback mode.
-B) Bcache does not find its cache
+B) Bcache does not find its cache::
host:/sys/block/md5/bcache# echo 0226553a-37cf-41d5-b3ce-8b1e944543a8 > attach
[ 1933.455082] bcache: bch_cached_dev_attach() Couldn't find uuid for md5 in set
@@ -160,7 +169,8 @@ B) Bcache does not find its cache
[ 1933.478179] : cache set not found
In this case, the caching device was simply not registered at boot
-or disappeared and came back, and needs to be (re-)registered:
+or disappeared and came back, and needs to be (re-)registered::
+
host:/sys/block/md5/bcache# echo /dev/sdh2 > /sys/fs/bcache/register
@@ -180,7 +190,8 @@ device is still available at an 8KiB offset. So either via a loopdev
of the backing device created with --offset 8K, or any value defined by
--data-offset when you originally formatted bcache with `make-bcache`.
-For example:
+For example::
+
losetup -o 8192 /dev/loop0 /dev/your_bcache_backing_dev
This should present your unmodified backing device data in /dev/loop0
@@ -191,33 +202,38 @@ cache device without loosing data.
E) Wiping a cache device
-host:~# wipefs -a /dev/sdh2
-16 bytes were erased at offset 0x1018 (bcache)
-they were: c6 85 73 f6 4e 1a 45 ca 82 65 f5 7f 48 ba 6d 81
-
-After you boot back with bcache enabled, you recreate the cache and attach it:
-host:~# make-bcache -C /dev/sdh2
-UUID: 7be7e175-8f4c-4f99-94b2-9c904d227045
-Set UUID: 5bc072a8-ab17-446d-9744-e247949913c1
-version: 0
-nbuckets: 106874
-block_size: 1
-bucket_size: 1024
-nr_in_set: 1
-nr_this_dev: 0
-first_bucket: 1
-[ 650.511912] bcache: run_cache_set() invalidating existing data
-[ 650.549228] bcache: register_cache() registered cache device sdh2
-
-start backing device with missing cache:
-host:/sys/block/md5/bcache# echo 1 > running
-
-attach new cache:
-host:/sys/block/md5/bcache# echo 5bc072a8-ab17-446d-9744-e247949913c1 > attach
-[ 865.276616] bcache: bch_cached_dev_attach() Caching md5 as bcache0 on set 5bc072a8-ab17-446d-9744-e247949913c1
-
-
-F) Remove or replace a caching device
+::
+
+ host:~# wipefs -a /dev/sdh2
+ 16 bytes were erased at offset 0x1018 (bcache)
+ they were: c6 85 73 f6 4e 1a 45 ca 82 65 f5 7f 48 ba 6d 81
+
+After you boot back with bcache enabled, you recreate the cache and attach it::
+
+ host:~# make-bcache -C /dev/sdh2
+ UUID: 7be7e175-8f4c-4f99-94b2-9c904d227045
+ Set UUID: 5bc072a8-ab17-446d-9744-e247949913c1
+ version: 0
+ nbuckets: 106874
+ block_size: 1
+ bucket_size: 1024
+ nr_in_set: 1
+ nr_this_dev: 0
+ first_bucket: 1
+ [ 650.511912] bcache: run_cache_set() invalidating existing data
+ [ 650.549228] bcache: register_cache() registered cache device sdh2
+
+start backing device with missing cache::
+
+ host:/sys/block/md5/bcache# echo 1 > running
+
+attach new cache::
+
+ host:/sys/block/md5/bcache# echo 5bc072a8-ab17-446d-9744-e247949913c1 > attach
+ [ 865.276616] bcache: bch_cached_dev_attach() Caching md5 as bcache0 on set 5bc072a8-ab17-446d-9744-e247949913c1
+
+
+F) Remove or replace a caching device::
host:/sys/block/sda/sda7/bcache# echo 1 > detach
[ 695.872542] bcache: cached_dev_detach_finish() Caching disabled for sda7
@@ -226,13 +242,15 @@ F) Remove or replace a caching device
wipefs: error: /dev/nvme0n1p4: probing initialization failed: Device or resource busy
Ooops, it's disabled, but not unregistered, so it's still protected
-We need to go and unregister it:
+We need to go and unregister it::
+
host:/sys/fs/bcache/b7ba27a1-2398-4649-8ae3-0959f57ba128# ls -l cache0
lrwxrwxrwx 1 root root 0 Feb 25 18:33 cache0 -> ../../../devices/pci0000:00/0000:00:1d.0/0000:70:00.0/nvme/nvme0/nvme0n1/nvme0n1p4/bcache/
host:/sys/fs/bcache/b7ba27a1-2398-4649-8ae3-0959f57ba128# echo 1 > stop
kernel: [ 917.041908] bcache: cache_set_free() Cache set b7ba27a1-2398-4649-8ae3-0959f57ba128 unregistered
-Now we can wipe it:
+Now we can wipe it::
+
host:~# wipefs -a /dev/nvme0n1p4
/dev/nvme0n1p4: 16 bytes were erased at offset 0x00001018 (bcache): c6 85 73 f6 4e 1a 45 ca 82 65 f5 7f 48 ba 6d 81
@@ -252,40 +270,44 @@ if there are any active backing or caching devices left on it:
1) Is it present in /dev/bcache* ? (there are times where it won't be)
-If so, it's easy:
+ If so, it's easy::
+
host:/sys/block/bcache0/bcache# echo 1 > stop
-2) But if your backing device is gone, this won't work:
+2) But if your backing device is gone, this won't work::
+
host:/sys/block/bcache0# cd bcache
bash: cd: bcache: No such file or directory
-In this case, you may have to unregister the dmcrypt block device that
-references this bcache to free it up:
+ In this case, you may have to unregister the dmcrypt block device that
+ references this bcache to free it up::
+
host:~# dmsetup remove oldds1
bcache: bcache_device_free() bcache0 stopped
bcache: cache_set_free() Cache set 5bc072a8-ab17-446d-9744-e247949913c1 unregistered
-This causes the backing bcache to be removed from /sys/fs/bcache and
-then it can be reused. This would be true of any block device stacking
-where bcache is a lower device.
+ This causes the backing bcache to be removed from /sys/fs/bcache and
+ then it can be reused. This would be true of any block device stacking
+ where bcache is a lower device.
-3) In other cases, you can also look in /sys/fs/bcache/:
+3) In other cases, you can also look in /sys/fs/bcache/::
-host:/sys/fs/bcache# ls -l */{cache?,bdev?}
-lrwxrwxrwx 1 root root 0 Mar 5 09:39 0226553a-37cf-41d5-b3ce-8b1e944543a8/bdev1 -> ../../../devices/virtual/block/dm-1/bcache/
-lrwxrwxrwx 1 root root 0 Mar 5 09:39 0226553a-37cf-41d5-b3ce-8b1e944543a8/cache0 -> ../../../devices/virtual/block/dm-4/bcache/
-lrwxrwxrwx 1 root root 0 Mar 5 09:39 5bc072a8-ab17-446d-9744-e247949913c1/cache0 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/ata10/host9/target9:0:0/9:0:0:0/block/sdl/sdl2/bcache/
+ host:/sys/fs/bcache# ls -l */{cache?,bdev?}
+ lrwxrwxrwx 1 root root 0 Mar 5 09:39 0226553a-37cf-41d5-b3ce-8b1e944543a8/bdev1 -> ../../../devices/virtual/block/dm-1/bcache/
+ lrwxrwxrwx 1 root root 0 Mar 5 09:39 0226553a-37cf-41d5-b3ce-8b1e944543a8/cache0 -> ../../../devices/virtual/block/dm-4/bcache/
+ lrwxrwxrwx 1 root root 0 Mar 5 09:39 5bc072a8-ab17-446d-9744-e247949913c1/cache0 -> ../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0/ata10/host9/target9:0:0/9:0:0:0/block/sdl/sdl2/bcache/
+
+ The device names will show which UUID is relevant, cd in that directory
+ and stop the cache::
-The device names will show which UUID is relevant, cd in that directory
-and stop the cache:
host:/sys/fs/bcache/5bc072a8-ab17-446d-9744-e247949913c1# echo 1 > stop
-This will free up bcache references and let you reuse the partition for
-other purposes.
+ This will free up bcache references and let you reuse the partition for
+ other purposes.
-TROUBLESHOOTING PERFORMANCE
+Troubleshooting performance
---------------------------
Bcache has a bunch of config options and tunables. The defaults are intended to
@@ -301,11 +323,13 @@ want for getting the best possible numbers when benchmarking.
raid stripe size to get the disk multiples that you would like.
For example: If you have a 64k stripe size, then the following offset
- would provide alignment for many common RAID5 data spindle counts:
+ would provide alignment for many common RAID5 data spindle counts::
+
64k * 2*2*2*3*3*5*7 bytes = 161280k
That space is wasted, but for only 157.5MB you can grow your RAID 5
- volume to the following data-spindle counts without re-aligning:
+ volume to the following data-spindle counts without re-aligning::
+
3,4,5,6,7,8,9,10,12,14,15,18,20,21 ...
- Bad write performance
@@ -313,9 +337,9 @@ want for getting the best possible numbers when benchmarking.
If write performance is not what you expected, you probably wanted to be
running in writeback mode, which isn't the default (not due to a lack of
maturity, but simply because in writeback mode you'll lose data if something
- happens to your SSD)
+ happens to your SSD)::
- # echo writeback > /sys/block/bcache0/bcache/cache_mode
+ # echo writeback > /sys/block/bcache0/bcache/cache_mode
- Bad performance, or traffic not going to the SSD that you'd expect
@@ -325,13 +349,13 @@ want for getting the best possible numbers when benchmarking.
accessed data out of your cache.
But if you want to benchmark reads from cache, and you start out with fio
- writing an 8 gigabyte test file - so you want to disable that.
+ writing an 8 gigabyte test file - so you want to disable that::
- # echo 0 > /sys/block/bcache0/bcache/sequential_cutoff
+ # echo 0 > /sys/block/bcache0/bcache/sequential_cutoff
- To set it back to the default (4 mb), do
+ To set it back to the default (4 mb), do::
- # echo 4M > /sys/block/bcache0/bcache/sequential_cutoff
+ # echo 4M > /sys/block/bcache0/bcache/sequential_cutoff
- Traffic's still going to the spindle/still getting cache misses
@@ -344,10 +368,10 @@ want for getting the best possible numbers when benchmarking.
throttles traffic if the latency exceeds a threshold (it does this by
cranking down the sequential bypass).
- You can disable this if you need to by setting the thresholds to 0:
+ You can disable this if you need to by setting the thresholds to 0::
- # echo 0 > /sys/fs/bcache/<cache set>/congested_read_threshold_us
- # echo 0 > /sys/fs/bcache/<cache set>/congested_write_threshold_us
+ # echo 0 > /sys/fs/bcache/<cache set>/congested_read_threshold_us
+ # echo 0 > /sys/fs/bcache/<cache set>/congested_write_threshold_us
The default is 2000 us (2 milliseconds) for reads, and 20000 for writes.
@@ -369,7 +393,7 @@ want for getting the best possible numbers when benchmarking.
a fix for the issue there).
-SYSFS - BACKING DEVICE
+Sysfs - backing device
----------------------
Available at /sys/block/<bdev>/bcache, /sys/block/bcache*/bcache and
@@ -454,7 +478,8 @@ writeback_running
still be added to the cache until it is mostly full; only meant for
benchmarking. Defaults to on.
-SYSFS - BACKING DEVICE STATS:
+Sysfs - backing device stats
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
There are directories with these numbers for a running total, as well as
versions that decay over the past day, hour and 5 minutes; they're also
@@ -463,14 +488,11 @@ aggregated in the cache set directory as well.
bypassed
Amount of IO (both reads and writes) that has bypassed the cache
-cache_hits
-cache_misses
-cache_hit_ratio
+cache_hits, cache_misses, cache_hit_ratio
Hits and misses are counted per individual IO as bcache sees them; a
partial hit is counted as a miss.
-cache_bypass_hits
-cache_bypass_misses
+cache_bypass_hits, cache_bypass_misses
Hits and misses for IO that is intended to skip the cache are still counted,
but broken out here.
@@ -482,7 +504,8 @@ cache_miss_collisions
cache_readaheads
Count of times readahead occurred.
-SYSFS - CACHE SET:
+Sysfs - cache set
+~~~~~~~~~~~~~~~~~
Available at /sys/fs/bcache/<cset-uuid>
@@ -520,8 +543,7 @@ flash_vol_create
Echoing a size to this file (in human readable units, k/M/G) creates a thinly
provisioned volume backed by the cache set.
-io_error_halflife
-io_error_limit
+io_error_halflife, io_error_limit
These determines how many errors we accept before disabling the cache.
Each error is decayed by the half life (in # ios). If the decaying count
reaches io_error_limit dirty data is written out and the cache is disabled.
@@ -545,7 +567,8 @@ unregister
Detaches all backing devices and closes the cache devices; if dirty data is
present it will disable writeback caching and wait for it to be flushed.
-SYSFS - CACHE SET INTERNAL:
+Sysfs - cache set internal
+~~~~~~~~~~~~~~~~~~~~~~~~~~
This directory also exposes timings for a number of internal operations, with
separate files for average duration, average frequency, last occurrence and max
@@ -574,7 +597,8 @@ cache_read_races
trigger_gc
Writing to this file forces garbage collection to run.
-SYSFS - CACHE DEVICE:
+Sysfs - Cache device
+~~~~~~~~~~~~~~~~~~~~
Available at /sys/block/<cdev>/bcache
--
2.9.4
[toc] | [next] | [standalone]
| From | Mauro Carvalho Chehab <mchehab@s-opensource.com> |
|---|---|
| Date | 2017-06-17 17:50 +0200 |
| Subject | [PATCH v2 13/31] DMA-API.txt: standardize document format |
| Message-ID | <tTo95-Gz-47@gated-at.bofh.it> |
| In reply to | #1668353 |
Each text file under Documentation follows a different
format. Some doesn't even have titles!
Change its representation to follow the adopted standard,
using ReST markups for it to be parseable by Sphinx:
- Fix some title marks to match ReST;
- use :Author: for author name;
- foo_ is an hyperlink. Get rid of it;
- Mark literal blocks as such;
- Use tables on some places that are almost using the
table format.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
---
Documentation/DMA-API.txt | 576 ++++++++++++++++++++++++++--------------------
1 file changed, 327 insertions(+), 249 deletions(-)
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index 71200dfa0922..45b29326d719 100644
--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -1,7 +1,8 @@
- Dynamic DMA mapping using the generic device
- ============================================
+============================================
+Dynamic DMA mapping using the generic device
+============================================
- James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
+:Author: James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
This document describes the DMA API. For a more gentle introduction
of the API (and actual examples), see Documentation/DMA-API-HOWTO.txt.
@@ -12,10 +13,10 @@ machines. Unless you know that your driver absolutely has to support
non-consistent platforms (this is usually only legacy platforms) you
should only use the API described in part I.
-Part I - dma_ API
--------------------------------------
+Part I - dma_API
+----------------
-To get the dma_ API, you must #include <linux/dma-mapping.h>. This
+To get the dma_API, you must #include <linux/dma-mapping.h>. This
provides dma_addr_t and the interfaces described below.
A dma_addr_t can hold any valid DMA address for the platform. It can be
@@ -26,9 +27,11 @@ address space and the DMA address space.
Part Ia - Using large DMA-coherent buffers
------------------------------------------
-void *
-dma_alloc_coherent(struct device *dev, size_t size,
- dma_addr_t *dma_handle, gfp_t flag)
+::
+
+ void *
+ dma_alloc_coherent(struct device *dev, size_t size,
+ dma_addr_t *dma_handle, gfp_t flag)
Consistent memory is memory for which a write by either the device or
the processor can immediately be read by the processor or device
@@ -51,20 +54,24 @@ consolidate your requests for consistent memory as much as possible.
The simplest way to do that is to use the dma_pool calls (see below).
The flag parameter (dma_alloc_coherent() only) allows the caller to
-specify the GFP_ flags (see kmalloc()) for the allocation (the
+specify the ``GFP_`` flags (see kmalloc()) for the allocation (the
implementation may choose to ignore flags that affect the location of
the returned memory, like GFP_DMA).
-void *
-dma_zalloc_coherent(struct device *dev, size_t size,
- dma_addr_t *dma_handle, gfp_t flag)
+::
+
+ void *
+ dma_zalloc_coherent(struct device *dev, size_t size,
+ dma_addr_t *dma_handle, gfp_t flag)
Wraps dma_alloc_coherent() and also zeroes the returned memory if the
allocation attempt succeeded.
-void
-dma_free_coherent(struct device *dev, size_t size, void *cpu_addr,
- dma_addr_t dma_handle)
+::
+
+ void
+ dma_free_coherent(struct device *dev, size_t size, void *cpu_addr,
+ dma_addr_t dma_handle)
Free a region of consistent memory you previously allocated. dev,
size and dma_handle must all be the same as those passed into
@@ -78,7 +85,7 @@ may only be called with IRQs enabled.
Part Ib - Using small DMA-coherent buffers
------------------------------------------
-To get this part of the dma_ API, you must #include <linux/dmapool.h>
+To get this part of the dma_API, you must #include <linux/dmapool.h>
Many drivers need lots of small DMA-coherent memory regions for DMA
descriptors or I/O buffers. Rather than allocating in units of a page
@@ -88,6 +95,8 @@ not __get_free_pages(). Also, they understand common hardware constraints
for alignment, like queue heads needing to be aligned on N-byte boundaries.
+::
+
struct dma_pool *
dma_pool_create(const char *name, struct device *dev,
size_t size, size_t align, size_t alloc);
@@ -103,16 +112,21 @@ in bytes, and must be a power of two). If your device has no boundary
crossing restrictions, pass 0 for alloc; passing 4096 says memory allocated
from this pool must not cross 4KByte boundaries.
+::
- void *dma_pool_zalloc(struct dma_pool *pool, gfp_t mem_flags,
- dma_addr_t *handle)
+ void *
+ dma_pool_zalloc(struct dma_pool *pool, gfp_t mem_flags,
+ dma_addr_t *handle)
Wraps dma_pool_alloc() and also zeroes the returned memory if the
allocation attempt succeeded.
- void *dma_pool_alloc(struct dma_pool *pool, gfp_t gfp_flags,
- dma_addr_t *dma_handle);
+::
+
+ void *
+ dma_pool_alloc(struct dma_pool *pool, gfp_t gfp_flags,
+ dma_addr_t *dma_handle);
This allocates memory from the pool; the returned memory will meet the
size and alignment requirements specified at creation time. Pass
@@ -122,16 +136,20 @@ blocking. Like dma_alloc_coherent(), this returns two values: an
address usable by the CPU, and the DMA address usable by the pool's
device.
+::
- void dma_pool_free(struct dma_pool *pool, void *vaddr,
- dma_addr_t addr);
+ void
+ dma_pool_free(struct dma_pool *pool, void *vaddr,
+ dma_addr_t addr);
This puts memory back into the pool. The pool is what was passed to
dma_pool_alloc(); the CPU (vaddr) and DMA addresses are what
were returned when that routine allocated the memory being freed.
+::
- void dma_pool_destroy(struct dma_pool *pool);
+ void
+ dma_pool_destroy(struct dma_pool *pool);
dma_pool_destroy() frees the resources of the pool. It must be
called in a context which can sleep. Make sure you've freed all allocated
@@ -141,32 +159,40 @@ memory back to the pool before you destroy it.
Part Ic - DMA addressing limitations
------------------------------------
-int
-dma_set_mask_and_coherent(struct device *dev, u64 mask)
+::
+
+ int
+ dma_set_mask_and_coherent(struct device *dev, u64 mask)
Checks to see if the mask is possible and updates the device
streaming and coherent DMA mask parameters if it is.
Returns: 0 if successful and a negative error if not.
-int
-dma_set_mask(struct device *dev, u64 mask)
+::
+
+ int
+ dma_set_mask(struct device *dev, u64 mask)
Checks to see if the mask is possible and updates the device
parameters if it is.
Returns: 0 if successful and a negative error if not.
-int
-dma_set_coherent_mask(struct device *dev, u64 mask)
+::
+
+ int
+ dma_set_coherent_mask(struct device *dev, u64 mask)
Checks to see if the mask is possible and updates the device
parameters if it is.
Returns: 0 if successful and a negative error if not.
-u64
-dma_get_required_mask(struct device *dev)
+::
+
+ u64
+ dma_get_required_mask(struct device *dev)
This API returns the mask that the platform requires to
operate efficiently. Usually this means the returned mask
@@ -182,94 +208,107 @@ call to set the mask to the value returned.
Part Id - Streaming DMA mappings
--------------------------------
-dma_addr_t
-dma_map_single(struct device *dev, void *cpu_addr, size_t size,
- enum dma_data_direction direction)
+::
+
+ dma_addr_t
+ dma_map_single(struct device *dev, void *cpu_addr, size_t size,
+ enum dma_data_direction direction)
Maps a piece of processor virtual memory so it can be accessed by the
device and returns the DMA address of the memory.
The direction for both APIs may be converted freely by casting.
-However the dma_ API uses a strongly typed enumerator for its
+However the dma_API uses a strongly typed enumerator for its
direction:
+======================= =============================================
DMA_NONE no direction (used for debugging)
DMA_TO_DEVICE data is going from the memory to the device
DMA_FROM_DEVICE data is coming from the device to the memory
DMA_BIDIRECTIONAL direction isn't known
+======================= =============================================
-Notes: Not all memory regions in a machine can be mapped by this API.
-Further, contiguous kernel virtual space may not be contiguous as
-physical memory. Since this API does not provide any scatter/gather
-capability, it will fail if the user tries to map a non-physically
-contiguous piece of memory. For this reason, memory to be mapped by
-this API should be obtained from sources which guarantee it to be
-physically contiguous (like kmalloc).
-
-Further, the DMA address of the memory must be within the
-dma_mask of the device (the dma_mask is a bit mask of the
-addressable region for the device, i.e., if the DMA address of
-the memory ANDed with the dma_mask is still equal to the DMA
-address, then the device can perform DMA to the memory). To
-ensure that the memory allocated by kmalloc is within the dma_mask,
-the driver may specify various platform-dependent flags to restrict
-the DMA address range of the allocation (e.g., on x86, GFP_DMA
-guarantees to be within the first 16MB of available DMA addresses,
-as required by ISA devices).
-
-Note also that the above constraints on physical contiguity and
-dma_mask may not apply if the platform has an IOMMU (a device which
-maps an I/O DMA address to a physical memory address). However, to be
-portable, device driver writers may *not* assume that such an IOMMU
-exists.
-
-Warnings: Memory coherency operates at a granularity called the cache
-line width. In order for memory mapped by this API to operate
-correctly, the mapped region must begin exactly on a cache line
-boundary and end exactly on one (to prevent two separately mapped
-regions from sharing a single cache line). Since the cache line size
-may not be known at compile time, the API will not enforce this
-requirement. Therefore, it is recommended that driver writers who
-don't take special care to determine the cache line size at run time
-only map virtual regions that begin and end on page boundaries (which
-are guaranteed also to be cache line boundaries).
-
-DMA_TO_DEVICE synchronisation must be done after the last modification
-of the memory region by the software and before it is handed off to
-the device. Once this primitive is used, memory covered by this
-primitive should be treated as read-only by the device. If the device
-may write to it at any point, it should be DMA_BIDIRECTIONAL (see
-below).
-
-DMA_FROM_DEVICE synchronisation must be done before the driver
-accesses data that may be changed by the device. This memory should
-be treated as read-only by the driver. If the driver needs to write
-to it at any point, it should be DMA_BIDIRECTIONAL (see below).
-
-DMA_BIDIRECTIONAL requires special handling: it means that the driver
-isn't sure if the memory was modified before being handed off to the
-device and also isn't sure if the device will also modify it. Thus,
-you must always sync bidirectional memory twice: once before the
-memory is handed off to the device (to make sure all memory changes
-are flushed from the processor) and once before the data may be
-accessed after being used by the device (to make sure any processor
-cache lines are updated with data that the device may have changed).
-
-void
-dma_unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
- enum dma_data_direction direction)
+.. note::
+
+ Not all memory regions in a machine can be mapped by this API.
+ Further, contiguous kernel virtual space may not be contiguous as
+ physical memory. Since this API does not provide any scatter/gather
+ capability, it will fail if the user tries to map a non-physically
+ contiguous piece of memory. For this reason, memory to be mapped by
+ this API should be obtained from sources which guarantee it to be
+ physically contiguous (like kmalloc).
+
+ Further, the DMA address of the memory must be within the
+ dma_mask of the device (the dma_mask is a bit mask of the
+ addressable region for the device, i.e., if the DMA address of
+ the memory ANDed with the dma_mask is still equal to the DMA
+ address, then the device can perform DMA to the memory). To
+ ensure that the memory allocated by kmalloc is within the dma_mask,
+ the driver may specify various platform-dependent flags to restrict
+ the DMA address range of the allocation (e.g., on x86, GFP_DMA
+ guarantees to be within the first 16MB of available DMA addresses,
+ as required by ISA devices).
+
+ Note also that the above constraints on physical contiguity and
+ dma_mask may not apply if the platform has an IOMMU (a device which
+ maps an I/O DMA address to a physical memory address). However, to be
+ portable, device driver writers may *not* assume that such an IOMMU
+ exists.
+
+.. warning::
+
+ Memory coherency operates at a granularity called the cache
+ line width. In order for memory mapped by this API to operate
+ correctly, the mapped region must begin exactly on a cache line
+ boundary and end exactly on one (to prevent two separately mapped
+ regions from sharing a single cache line). Since the cache line size
+ may not be known at compile time, the API will not enforce this
+ requirement. Therefore, it is recommended that driver writers who
+ don't take special care to determine the cache line size at run time
+ only map virtual regions that begin and end on page boundaries (which
+ are guaranteed also to be cache line boundaries).
+
+ DMA_TO_DEVICE synchronisation must be done after the last modification
+ of the memory region by the software and before it is handed off to
+ the device. Once this primitive is used, memory covered by this
+ primitive should be treated as read-only by the device. If the device
+ may write to it at any point, it should be DMA_BIDIRECTIONAL (see
+ below).
+
+ DMA_FROM_DEVICE synchronisation must be done before the driver
+ accesses data that may be changed by the device. This memory should
+ be treated as read-only by the driver. If the driver needs to write
+ to it at any point, it should be DMA_BIDIRECTIONAL (see below).
+
+ DMA_BIDIRECTIONAL requires special handling: it means that the driver
+ isn't sure if the memory was modified before being handed off to the
+ device and also isn't sure if the device will also modify it. Thus,
+ you must always sync bidirectional memory twice: once before the
+ memory is handed off to the device (to make sure all memory changes
+ are flushed from the processor) and once before the data may be
+ accessed after being used by the device (to make sure any processor
+ cache lines are updated with data that the device may have changed).
+
+::
+
+ void
+ dma_unmap_single(struct device *dev, dma_addr_t dma_addr, size_t size,
+ enum dma_data_direction direction)
Unmaps the region previously mapped. All the parameters passed in
must be identical to those passed in (and returned) by the mapping
API.
-dma_addr_t
-dma_map_page(struct device *dev, struct page *page,
- unsigned long offset, size_t size,
- enum dma_data_direction direction)
-void
-dma_unmap_page(struct device *dev, dma_addr_t dma_address, size_t size,
- enum dma_data_direction direction)
+::
+
+ dma_addr_t
+ dma_map_page(struct device *dev, struct page *page,
+ unsigned long offset, size_t size,
+ enum dma_data_direction direction)
+
+ void
+ dma_unmap_page(struct device *dev, dma_addr_t dma_address, size_t size,
+ enum dma_data_direction direction)
API for mapping and unmapping for pages. All the notes and warnings
for the other mapping APIs apply here. Also, although the <offset>
@@ -277,20 +316,24 @@ and <size> parameters are provided to do partial page mapping, it is
recommended that you never use these unless you really know what the
cache width is.
-dma_addr_t
-dma_map_resource(struct device *dev, phys_addr_t phys_addr, size_t size,
- enum dma_data_direction dir, unsigned long attrs)
+::
-void
-dma_unmap_resource(struct device *dev, dma_addr_t addr, size_t size,
- enum dma_data_direction dir, unsigned long attrs)
+ dma_addr_t
+ dma_map_resource(struct device *dev, phys_addr_t phys_addr, size_t size,
+ enum dma_data_direction dir, unsigned long attrs)
+
+ void
+ dma_unmap_resource(struct device *dev, dma_addr_t addr, size_t size,
+ enum dma_data_direction dir, unsigned long attrs)
API for mapping and unmapping for MMIO resources. All the notes and
warnings for the other mapping APIs apply here. The API should only be
used to map device MMIO resources, mapping of RAM is not permitted.
-int
-dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
+::
+
+ int
+ dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
In some circumstances dma_map_single(), dma_map_page() and dma_map_resource()
will fail to create a mapping. A driver can check for these errors by testing
@@ -298,9 +341,11 @@ the returned DMA address with dma_mapping_error(). A non-zero return value
means the mapping could not be created and the driver should take appropriate
action (e.g. reduce current DMA mapping usage or delay and try again later).
+::
+
int
dma_map_sg(struct device *dev, struct scatterlist *sg,
- int nents, enum dma_data_direction direction)
+ int nents, enum dma_data_direction direction)
Returns: the number of DMA address segments mapped (this may be shorter
than <nents> passed in if some elements of the scatter/gather list are
@@ -316,7 +361,7 @@ critical that the driver do something, in the case of a block driver
aborting the request or even oopsing is better than doing nothing and
corrupting the filesystem.
-With scatterlists, you use the resulting mapping like this:
+With scatterlists, you use the resulting mapping like this::
int i, count = dma_map_sg(dev, sglist, nents, direction);
struct scatterlist *sg;
@@ -337,9 +382,11 @@ Then you should loop count times (note: this can be less than nents times)
and use sg_dma_address() and sg_dma_len() macros where you previously
accessed sg->address and sg->length as shown above.
+::
+
void
dma_unmap_sg(struct device *dev, struct scatterlist *sg,
- int nents, enum dma_data_direction direction)
+ int nents, enum dma_data_direction direction)
Unmap the previously mapped scatter/gather list. All the parameters
must be the same as those and passed in to the scatter/gather mapping
@@ -348,18 +395,27 @@ API.
Note: <nents> must be the number you passed in, *not* the number of
DMA address entries returned.
-void
-dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle, size_t size,
- enum dma_data_direction direction)
-void
-dma_sync_single_for_device(struct device *dev, dma_addr_t dma_handle, size_t size,
- enum dma_data_direction direction)
-void
-dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int nents,
- enum dma_data_direction direction)
-void
-dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg, int nents,
- enum dma_data_direction direction)
+::
+
+ void
+ dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle,
+ size_t size,
+ enum dma_data_direction direction)
+
+ void
+ dma_sync_single_for_device(struct device *dev, dma_addr_t dma_handle,
+ size_t size,
+ enum dma_data_direction direction)
+
+ void
+ dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
+ int nents,
+ enum dma_data_direction direction)
+
+ void
+ dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
+ int nents,
+ enum dma_data_direction direction)
Synchronise a single contiguous or scatter/gather mapping for the CPU
and device. With the sync_sg API, all the parameters must be the same
@@ -367,36 +423,41 @@ as those passed into the single mapping API. With the sync_single API,
you can use dma_handle and size parameters that aren't identical to
those passed into the single mapping API to do a partial sync.
-Notes: You must do this:
-- Before reading values that have been written by DMA from the device
- (use the DMA_FROM_DEVICE direction)
-- After writing values that will be written to the device using DMA
- (use the DMA_TO_DEVICE) direction
-- before *and* after handing memory to the device if the memory is
- DMA_BIDIRECTIONAL
+.. note::
+
+ You must do this:
+
+ - Before reading values that have been written by DMA from the device
+ (use the DMA_FROM_DEVICE direction)
+ - After writing values that will be written to the device using DMA
+ (use the DMA_TO_DEVICE) direction
+ - before *and* after handing memory to the device if the memory is
+ DMA_BIDIRECTIONAL
See also dma_map_single().
-dma_addr_t
-dma_map_single_attrs(struct device *dev, void *cpu_addr, size_t size,
- enum dma_data_direction dir,
- unsigned long attrs)
+::
-void
-dma_unmap_single_attrs(struct device *dev, dma_addr_t dma_addr,
- size_t size, enum dma_data_direction dir,
- unsigned long attrs)
+ dma_addr_t
+ dma_map_single_attrs(struct device *dev, void *cpu_addr, size_t size,
+ enum dma_data_direction dir,
+ unsigned long attrs)
-int
-dma_map_sg_attrs(struct device *dev, struct scatterlist *sgl,
- int nents, enum dma_data_direction dir,
- unsigned long attrs)
+ void
+ dma_unmap_single_attrs(struct device *dev, dma_addr_t dma_addr,
+ size_t size, enum dma_data_direction dir,
+ unsigned long attrs)
-void
-dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sgl,
- int nents, enum dma_data_direction dir,
- unsigned long attrs)
+ int
+ dma_map_sg_attrs(struct device *dev, struct scatterlist *sgl,
+ int nents, enum dma_data_direction dir,
+ unsigned long attrs)
+
+ void
+ dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sgl,
+ int nents, enum dma_data_direction dir,
+ unsigned long attrs)
The four functions above are just like the counterpart functions
without the _attrs suffixes, except that they pass an optional
@@ -410,37 +471,38 @@ is identical to those of the corresponding function
without the _attrs suffix. As a result dma_map_single_attrs()
can generally replace dma_map_single(), etc.
-As an example of the use of the *_attrs functions, here's how
+As an example of the use of the ``*_attrs`` functions, here's how
you could pass an attribute DMA_ATTR_FOO when mapping memory
-for DMA:
+for DMA::
-#include <linux/dma-mapping.h>
-/* DMA_ATTR_FOO should be defined in linux/dma-mapping.h and
- * documented in Documentation/DMA-attributes.txt */
-...
+ #include <linux/dma-mapping.h>
+ /* DMA_ATTR_FOO should be defined in linux/dma-mapping.h and
+ * documented in Documentation/DMA-attributes.txt */
+ ...
- unsigned long attr;
- attr |= DMA_ATTR_FOO;
- ....
- n = dma_map_sg_attrs(dev, sg, nents, DMA_TO_DEVICE, attr);
- ....
+ unsigned long attr;
+ attr |= DMA_ATTR_FOO;
+ ....
+ n = dma_map_sg_attrs(dev, sg, nents, DMA_TO_DEVICE, attr);
+ ....
Architectures that care about DMA_ATTR_FOO would check for its
presence in their implementations of the mapping and unmapping
-routines, e.g.:
+routines, e.g.:::
-void whizco_dma_map_sg_attrs(struct device *dev, dma_addr_t dma_addr,
- size_t size, enum dma_data_direction dir,
- unsigned long attrs)
-{
- ....
- if (attrs & DMA_ATTR_FOO)
- /* twizzle the frobnozzle */
- ....
+ void whizco_dma_map_sg_attrs(struct device *dev, dma_addr_t dma_addr,
+ size_t size, enum dma_data_direction dir,
+ unsigned long attrs)
+ {
+ ....
+ if (attrs & DMA_ATTR_FOO)
+ /* twizzle the frobnozzle */
+ ....
+ }
-Part II - Advanced dma_ usage
------------------------------
+Part II - Advanced dma usage
+----------------------------
Warning: These pieces of the DMA API should not be used in the
majority of cases, since they cater for unlikely corner cases that
@@ -450,9 +512,11 @@ If you don't understand how cache line coherency works between a
processor and an I/O device, you should not be using this part of the
API at all.
-void *
-dma_alloc_noncoherent(struct device *dev, size_t size,
- dma_addr_t *dma_handle, gfp_t flag)
+::
+
+ void *
+ dma_alloc_noncoherent(struct device *dev, size_t size,
+ dma_addr_t *dma_handle, gfp_t flag)
Identical to dma_alloc_coherent() except that the platform will
choose to return either consistent or non-consistent memory as it sees
@@ -468,39 +532,49 @@ only use this API if you positively know your driver will be
required to work on one of the rare (usually non-PCI) architectures
that simply cannot make consistent memory.
-void
-dma_free_noncoherent(struct device *dev, size_t size, void *cpu_addr,
- dma_addr_t dma_handle)
+::
+
+ void
+ dma_free_noncoherent(struct device *dev, size_t size, void *cpu_addr,
+ dma_addr_t dma_handle)
Free memory allocated by the nonconsistent API. All parameters must
be identical to those passed in (and returned by
dma_alloc_noncoherent()).
-int
-dma_get_cache_alignment(void)
+::
+
+ int
+ dma_get_cache_alignment(void)
Returns the processor cache alignment. This is the absolute minimum
alignment *and* width that you must observe when either mapping
memory or doing partial flushes.
-Notes: This API may return a number *larger* than the actual cache
-line, but it will guarantee that one or more cache lines fit exactly
-into the width returned by this call. It will also always be a power
-of two for easy alignment.
+.. note::
-void
-dma_cache_sync(struct device *dev, void *vaddr, size_t size,
- enum dma_data_direction direction)
+ This API may return a number *larger* than the actual cache
+ line, but it will guarantee that one or more cache lines fit exactly
+ into the width returned by this call. It will also always be a power
+ of two for easy alignment.
+
+::
+
+ void
+ dma_cache_sync(struct device *dev, void *vaddr, size_t size,
+ enum dma_data_direction direction)
Do a partial sync of memory that was allocated by
dma_alloc_noncoherent(), starting at virtual address vaddr and
continuing on for size. Again, you *must* observe the cache line
boundaries when doing this.
-int
-dma_declare_coherent_memory(struct device *dev, phys_addr_t phys_addr,
- dma_addr_t device_addr, size_t size, int
- flags)
+::
+
+ int
+ dma_declare_coherent_memory(struct device *dev, phys_addr_t phys_addr,
+ dma_addr_t device_addr, size_t size, int
+ flags)
Declare region of memory to be handed out by dma_alloc_coherent() when
it's asked for coherent memory for this device.
@@ -516,21 +590,21 @@ size is the size of the area (must be multiples of PAGE_SIZE).
flags can be ORed together and are:
-DMA_MEMORY_MAP - request that the memory returned from
-dma_alloc_coherent() be directly writable.
+- DMA_MEMORY_MAP - request that the memory returned from
+ dma_alloc_coherent() be directly writable.
-DMA_MEMORY_IO - request that the memory returned from
-dma_alloc_coherent() be addressable using read()/write()/memcpy_toio() etc.
+- DMA_MEMORY_IO - request that the memory returned from
+ dma_alloc_coherent() be addressable using read()/write()/memcpy_toio() etc.
One or both of these flags must be present.
-DMA_MEMORY_INCLUDES_CHILDREN - make the declared memory be allocated by
-dma_alloc_coherent of any child devices of this one (for memory residing
-on a bridge).
+- DMA_MEMORY_INCLUDES_CHILDREN - make the declared memory be allocated by
+ dma_alloc_coherent of any child devices of this one (for memory residing
+ on a bridge).
-DMA_MEMORY_EXCLUSIVE - only allocate memory from the declared regions.
-Do not allow dma_alloc_coherent() to fall back to system memory when
-it's out of memory in the declared region.
+- DMA_MEMORY_EXCLUSIVE - only allocate memory from the declared regions.
+ Do not allow dma_alloc_coherent() to fall back to system memory when
+ it's out of memory in the declared region.
The return value will be either DMA_MEMORY_MAP or DMA_MEMORY_IO and
must correspond to a passed in flag (i.e. no returning DMA_MEMORY_IO
@@ -543,15 +617,17 @@ must be accessed using the correct bus functions. If your driver
isn't prepared to handle this contingency, it should not specify
DMA_MEMORY_IO in the input flags.
-As a simplification for the platforms, only *one* such region of
+As a simplification for the platforms, only **one** such region of
memory may be declared per device.
For reasons of efficiency, most platforms choose to track the declared
region only at the granularity of a page. For smaller allocations,
you should use the dma_pool() API.
-void
-dma_release_declared_memory(struct device *dev)
+::
+
+ void
+ dma_release_declared_memory(struct device *dev)
Remove the memory region previously declared from the system. This
API performs *no* in-use checking for this region and will return
@@ -559,9 +635,11 @@ unconditionally having removed all the required structures. It is the
driver's job to ensure that no parts of this memory region are
currently in use.
-void *
-dma_mark_declared_memory_occupied(struct device *dev,
- dma_addr_t device_addr, size_t size)
+::
+
+ void *
+ dma_mark_declared_memory_occupied(struct device *dev,
+ dma_addr_t device_addr, size_t size)
This is used to occupy specific regions of the declared space
(dma_alloc_coherent() will hand out the first free region it finds).
@@ -592,38 +670,37 @@ option has a performance impact. Do not enable it in production kernels.
If you boot the resulting kernel will contain code which does some bookkeeping
about what DMA memory was allocated for which device. If this code detects an
error it prints a warning message with some details into your kernel log. An
-example warning message may look like this:
+example warning message may look like this::
-------------[ cut here ]------------
-WARNING: at /data2/repos/linux-2.6-iommu/lib/dma-debug.c:448
- check_unmap+0x203/0x490()
-Hardware name:
-forcedeth 0000:00:08.0: DMA-API: device driver frees DMA memory with wrong
- function [device address=0x00000000640444be] [size=66 bytes] [mapped as
-single] [unmapped as page]
-Modules linked in: nfsd exportfs bridge stp llc r8169
-Pid: 0, comm: swapper Tainted: G W 2.6.28-dmatest-09289-g8bb99c0 #1
-Call Trace:
- <IRQ> [<ffffffff80240b22>] warn_slowpath+0xf2/0x130
- [<ffffffff80647b70>] _spin_unlock+0x10/0x30
- [<ffffffff80537e75>] usb_hcd_link_urb_to_ep+0x75/0xc0
- [<ffffffff80647c22>] _spin_unlock_irqrestore+0x12/0x40
- [<ffffffff8055347f>] ohci_urb_enqueue+0x19f/0x7c0
- [<ffffffff80252f96>] queue_work+0x56/0x60
- [<ffffffff80237e10>] enqueue_task_fair+0x20/0x50
- [<ffffffff80539279>] usb_hcd_submit_urb+0x379/0xbc0
- [<ffffffff803b78c3>] cpumask_next_and+0x23/0x40
- [<ffffffff80235177>] find_busiest_group+0x207/0x8a0
- [<ffffffff8064784f>] _spin_lock_irqsave+0x1f/0x50
- [<ffffffff803c7ea3>] check_unmap+0x203/0x490
- [<ffffffff803c8259>] debug_dma_unmap_page+0x49/0x50
- [<ffffffff80485f26>] nv_tx_done_optimized+0xc6/0x2c0
- [<ffffffff80486c13>] nv_nic_irq_optimized+0x73/0x2b0
- [<ffffffff8026df84>] handle_IRQ_event+0x34/0x70
- [<ffffffff8026ffe9>] handle_edge_irq+0xc9/0x150
- [<ffffffff8020e3ab>] do_IRQ+0xcb/0x1c0
- [<ffffffff8020c093>] ret_from_intr+0x0/0xa
- <EOI> <4>---[ end trace f6435a98e2a38c0e ]---
+ WARNING: at /data2/repos/linux-2.6-iommu/lib/dma-debug.c:448
+ check_unmap+0x203/0x490()
+ Hardware name:
+ forcedeth 0000:00:08.0: DMA-API: device driver frees DMA memory with wrong
+ function [device address=0x00000000640444be] [size=66 bytes] [mapped as
+ single] [unmapped as page]
+ Modules linked in: nfsd exportfs bridge stp llc r8169
+ Pid: 0, comm: swapper Tainted: G W 2.6.28-dmatest-09289-g8bb99c0 #1
+ Call Trace:
+ <IRQ> [<ffffffff80240b22>] warn_slowpath+0xf2/0x130
+ [<ffffffff80647b70>] _spin_unlock+0x10/0x30
+ [<ffffffff80537e75>] usb_hcd_link_urb_to_ep+0x75/0xc0
+ [<ffffffff80647c22>] _spin_unlock_irqrestore+0x12/0x40
+ [<ffffffff8055347f>] ohci_urb_enqueue+0x19f/0x7c0
+ [<ffffffff80252f96>] queue_work+0x56/0x60
+ [<ffffffff80237e10>] enqueue_task_fair+0x20/0x50
+ [<ffffffff80539279>] usb_hcd_submit_urb+0x379/0xbc0
+ [<ffffffff803b78c3>] cpumask_next_and+0x23/0x40
+ [<ffffffff80235177>] find_busiest_group+0x207/0x8a0
+ [<ffffffff8064784f>] _spin_lock_irqsave+0x1f/0x50
+ [<ffffffff803c7ea3>] check_unmap+0x203/0x490
+ [<ffffffff803c8259>] debug_dma_unmap_page+0x49/0x50
+ [<ffffffff80485f26>] nv_tx_done_optimized+0xc6/0x2c0
+ [<ffffffff80486c13>] nv_nic_irq_optimized+0x73/0x2b0
+ [<ffffffff8026df84>] handle_IRQ_event+0x34/0x70
+ [<ffffffff8026ffe9>] handle_edge_irq+0xc9/0x150
+ [<ffffffff8020e3ab>] do_IRQ+0xcb/0x1c0
+ [<ffffffff8020c093>] ret_from_intr+0x0/0xa
+ <EOI> <4>---[ end trace f6435a98e2a38c0e ]---
The driver developer can find the driver and the device including a stacktrace
of the DMA-API call which caused this warning.
@@ -637,43 +714,42 @@ details.
The debugfs directory for the DMA-API debugging code is called dma-api/. In
this directory the following files can currently be found:
- dma-api/all_errors This file contains a numeric value. If this
+=============================== ===============================================
+dma-api/all_errors This file contains a numeric value. If this
value is not equal to zero the debugging code
will print a warning for every error it finds
into the kernel log. Be careful with this
option, as it can easily flood your logs.
- dma-api/disabled This read-only file contains the character 'Y'
+dma-api/disabled This read-only file contains the character 'Y'
if the debugging code is disabled. This can
happen when it runs out of memory or if it was
disabled at boot time
- dma-api/error_count This file is read-only and shows the total
+dma-api/error_count This file is read-only and shows the total
numbers of errors found.
- dma-api/num_errors The number in this file shows how many
+dma-api/num_errors The number in this file shows how many
warnings will be printed to the kernel log
before it stops. This number is initialized to
one at system boot and be set by writing into
this file
- dma-api/min_free_entries
- This read-only file can be read to get the
+dma-api/min_free_entries This read-only file can be read to get the
minimum number of free dma_debug_entries the
allocator has ever seen. If this value goes
down to zero the code will disable itself
because it is not longer reliable.
- dma-api/num_free_entries
- The current number of free dma_debug_entries
+dma-api/num_free_entries The current number of free dma_debug_entries
in the allocator.
- dma-api/driver-filter
- You can write a name of a driver into this file
+dma-api/driver-filter You can write a name of a driver into this file
to limit the debug output to requests from that
particular driver. Write an empty string to
that file to disable the filter and see
all errors again.
+=============================== ===============================================
If you have this code compiled into your kernel it will be enabled by default.
If you want to boot without the bookkeeping anyway you can provide
@@ -692,7 +768,10 @@ of preallocated entries is defined per architecture. If it is too low for you
boot with 'dma_debug_entries=<your_desired_number>' to overwrite the
architectural default.
-void debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
+::
+
+ void
+ debug_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
dma-debug interface debug_dma_mapping_error() to debug drivers that fail
to check DMA mapping errors on addresses returned by dma_map_single() and
@@ -702,4 +781,3 @@ the driver. When driver does unmap, debug_dma_unmap() checks the flag and if
this flag is still set, prints warning message that includes call trace that
leads up to the unmap. This interface can be called from dma_mapping_error()
routines to enable DMA mapping error check debugging.
-
--
2.9.4
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| From | Mauro Carvalho Chehab <mchehab@s-opensource.com> |
|---|---|
| Date | 2017-06-17 17:50 +0200 |
| Subject | [PATCH v2 16/31] DMA-ISA-LPC.txt: standardize document format |
| Message-ID | <tTo95-Gz-49@gated-at.bofh.it> |
| In reply to | #1668353 |
Each text file under Documentation follows a different format. Some doesn't even have titles! Change its representation to follow the adopted standard, using ReST markups for it to be parseable by Sphinx: - use proper markups for titles; - use :Author: for authorship; - identify the literal blocks. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com> --- Documentation/DMA-ISA-LPC.txt | 71 ++++++++++++++++++++++--------------------- 1 file changed, 36 insertions(+), 35 deletions(-) diff --git a/Documentation/DMA-ISA-LPC.txt b/Documentation/DMA-ISA-LPC.txt index c41331398752..c44be1a2176f 100644 --- a/Documentation/DMA-ISA-LPC.txt +++ b/Documentation/DMA-ISA-LPC.txt @@ -1,19 +1,20 @@ - DMA with ISA and LPC devices - ============================ +============================ +DMA with ISA and LPC devices +============================ - Pierre Ossman <drzeus@drzeus.cx> +:Author: Pierre Ossman <drzeus@drzeus.cx> This document describes how to do DMA transfers using the old ISA DMA controller. Even though ISA is more or less dead today the LPC bus uses the same DMA system so it will be around for quite some time. -Part I - Headers and dependencies ---------------------------------- +Headers and dependencies +------------------------ -To do ISA style DMA you need to include two headers: +To do ISA style DMA you need to include two headers:: -#include <linux/dma-mapping.h> -#include <asm/dma.h> + #include <linux/dma-mapping.h> + #include <asm/dma.h> The first is the generic DMA API used to convert virtual addresses to bus addresses (see Documentation/DMA-API.txt for details). @@ -23,8 +24,8 @@ this is not present on all platforms make sure you construct your Kconfig to be dependent on ISA_DMA_API (not ISA) so that nobody tries to build your driver on unsupported platforms. -Part II - Buffer allocation ---------------------------- +Buffer allocation +----------------- The ISA DMA controller has some very strict requirements on which memory it can access so extra care must be taken when allocating @@ -47,8 +48,8 @@ __GFP_REPEAT and __GFP_NOWARN to make the allocator try a bit harder. (This scarcity also means that you should allocate the buffer as early as possible and not release it until the driver is unloaded.) -Part III - Address translation ------------------------------- +Address translation +------------------- To translate the virtual address to a bus address, use the normal DMA API. Do _not_ use isa_virt_to_phys() even though it does the same @@ -61,8 +62,8 @@ Note: x86_64 had a broken DMA API when it came to ISA but has since been fixed. If your arch has problems then fix the DMA API instead of reverting to the ISA functions. -Part IV - Channels ------------------- +Channels +-------- A normal ISA DMA controller has 8 channels. The lower four are for 8-bit transfers and the upper four are for 16-bit transfers. @@ -80,8 +81,8 @@ The ability to use 16-bit or 8-bit transfers is _not_ up to you as a driver author but depends on what the hardware supports. Check your specs or test different channels. -Part V - Transfer data ----------------------- +Transfer data +------------- Now for the good stuff, the actual DMA transfer. :) @@ -112,37 +113,37 @@ Once the DMA transfer is finished (or timed out) you should disable the channel again. You should also check get_dma_residue() to make sure that all data has been transferred. -Example: +Example:: -int flags, residue; + int flags, residue; -flags = claim_dma_lock(); + flags = claim_dma_lock(); -clear_dma_ff(); + clear_dma_ff(); -set_dma_mode(channel, DMA_MODE_WRITE); -set_dma_addr(channel, phys_addr); -set_dma_count(channel, num_bytes); + set_dma_mode(channel, DMA_MODE_WRITE); + set_dma_addr(channel, phys_addr); + set_dma_count(channel, num_bytes); -dma_enable(channel); + dma_enable(channel); -release_dma_lock(flags); + release_dma_lock(flags); -while (!device_done()); + while (!device_done()); -flags = claim_dma_lock(); + flags = claim_dma_lock(); -dma_disable(channel); + dma_disable(channel); -residue = dma_get_residue(channel); -if (residue != 0) - printk(KERN_ERR "driver: Incomplete DMA transfer!" - " %d bytes left!\n", residue); + residue = dma_get_residue(channel); + if (residue != 0) + printk(KERN_ERR "driver: Incomplete DMA transfer!" + " %d bytes left!\n", residue); -release_dma_lock(flags); + release_dma_lock(flags); -Part VI - Suspend/resume ------------------------- +Suspend/resume +-------------- It is the driver's responsibility to make sure that the machine isn't suspended while a DMA transfer is in progress. Also, all DMA settings -- 2.9.4
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| From | Mauro Carvalho Chehab <mchehab@s-opensource.com> |
|---|---|
| Date | 2017-06-17 17:50 +0200 |
| Subject | [PATCH v2 09/31] cputopology.txt: standardize document format |
| Message-ID | <tTo95-Gz-51@gated-at.bofh.it> |
| In reply to | #1668353 |
Each text file under Documentation follows a different
format. Some doesn't even have titles!
Change its representation to follow the adopted standard,
using ReST markups for it to be parseable by Sphinx:
- Add a title for the document;
- mark literals;
- use table markup for existing table.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
---
Documentation/cputopology.txt | 35 +++++++++++++++++++++--------------
1 file changed, 21 insertions(+), 14 deletions(-)
diff --git a/Documentation/cputopology.txt b/Documentation/cputopology.txt
index 127c9d8c2174..c6e7e9196a8b 100644
--- a/Documentation/cputopology.txt
+++ b/Documentation/cputopology.txt
@@ -1,3 +1,6 @@
+===========================================
+How CPU topology info is exported via sysfs
+===========================================
Export CPU topology info via sysfs. Items (attributes) are similar
to /proc/cpuinfo output of some architectures:
@@ -75,24 +78,26 @@ CONFIG_SCHED_BOOK and CONFIG_DRAWER are currently only used on s390, where
they reflect the cpu and cache hierarchy.
For an architecture to support this feature, it must define some of
-these macros in include/asm-XXX/topology.h:
-#define topology_physical_package_id(cpu)
-#define topology_core_id(cpu)
-#define topology_book_id(cpu)
-#define topology_drawer_id(cpu)
-#define topology_sibling_cpumask(cpu)
-#define topology_core_cpumask(cpu)
-#define topology_book_cpumask(cpu)
-#define topology_drawer_cpumask(cpu)
+these macros in include/asm-XXX/topology.h::
-The type of **_id macros is int.
-The type of **_cpumask macros is (const) struct cpumask *. The latter
-correspond with appropriate **_siblings sysfs attributes (except for
+ #define topology_physical_package_id(cpu)
+ #define topology_core_id(cpu)
+ #define topology_book_id(cpu)
+ #define topology_drawer_id(cpu)
+ #define topology_sibling_cpumask(cpu)
+ #define topology_core_cpumask(cpu)
+ #define topology_book_cpumask(cpu)
+ #define topology_drawer_cpumask(cpu)
+
+The type of ``**_id macros`` is int.
+The type of ``**_cpumask macros`` is ``(const) struct cpumask *``. The latter
+correspond with appropriate ``**_siblings`` sysfs attributes (except for
topology_sibling_cpumask() which corresponds with thread_siblings).
To be consistent on all architectures, include/linux/topology.h
provides default definitions for any of the above macros that are
not defined by include/asm-XXX/topology.h:
+
1) physical_package_id: -1
2) core_id: 0
3) sibling_cpumask: just the given CPU
@@ -107,6 +112,7 @@ Additionally, CPU topology information is provided under
/sys/devices/system/cpu and includes these files. The internal
source for the output is in brackets ("[]").
+ =========== ==========================================================
kernel_max: the maximum CPU index allowed by the kernel configuration.
[NR_CPUS-1]
@@ -122,6 +128,7 @@ source for the output is in brackets ("[]").
present: CPUs that have been identified as being present in the
system. [cpu_present_mask]
+ =========== ==========================================================
The format for the above output is compatible with cpulist_parse()
[see <linux/cpumask.h>]. Some examples follow.
@@ -129,7 +136,7 @@ The format for the above output is compatible with cpulist_parse()
In this example, there are 64 CPUs in the system but cpus 32-63 exceed
the kernel max which is limited to 0..31 by the NR_CPUS config option
being 32. Note also that CPUs 2 and 4-31 are not online but could be
-brought online as they are both present and possible.
+brought online as they are both present and possible::
kernel_max: 31
offline: 2,4-31,32-63
@@ -140,7 +147,7 @@ brought online as they are both present and possible.
In this example, the NR_CPUS config option is 128, but the kernel was
started with possible_cpus=144. There are 4 CPUs in the system and cpu2
was manually taken offline (and is the only CPU that can be brought
-online.)
+online.)::
kernel_max: 127
offline: 2,4-127,128-143
--
2.9.4
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| From | Mauro Carvalho Chehab <mchehab@s-opensource.com> |
|---|---|
| Date | 2017-06-17 17:50 +0200 |
| Subject | [PATCH v2 22/31] gcc-plugins.txt: standardize document format |
| Message-ID | <tTo95-Gz-53@gated-at.bofh.it> |
| In reply to | #1668353 |
Each text file under Documentation follows a different format. Some doesn't even have titles! Change its representation to follow the adopted standard, using ReST markups for it to be parseable by Sphinx: - promote main title; - use the right markup for footnotes; - use bold markup for files name; - identify literal blocks; - add blank lines to avoid Sphinx to complain; - remove numeration from titles. Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com> --- Documentation/gcc-plugins.txt | 58 ++++++++++++++++++++++++------------------- 1 file changed, 32 insertions(+), 26 deletions(-) diff --git a/Documentation/gcc-plugins.txt b/Documentation/gcc-plugins.txt index 433eaefb4aa1..8502f24396fb 100644 --- a/Documentation/gcc-plugins.txt +++ b/Documentation/gcc-plugins.txt @@ -1,14 +1,15 @@ +========================= GCC plugin infrastructure ========================= -1. Introduction -=============== +Introduction +============ GCC plugins are loadable modules that provide extra features to the -compiler [1]. They are useful for runtime instrumentation and static analysis. +compiler [1]_. They are useful for runtime instrumentation and static analysis. We can analyse, change and add further code during compilation via -callbacks [2], GIMPLE [3], IPA [4] and RTL passes [5]. +callbacks [2]_, GIMPLE [3]_, IPA [4]_ and RTL passes [5]_. The GCC plugin infrastructure of the kernel supports all gcc versions from 4.5 to 6.0, building out-of-tree modules, cross-compilation and building in a @@ -21,56 +22,61 @@ and versions 4.8+ can only be compiled by a C++ compiler. Currently the GCC plugin infrastructure supports only the x86, arm, arm64 and powerpc architectures. -This infrastructure was ported from grsecurity [6] and PaX [7]. +This infrastructure was ported from grsecurity [6]_ and PaX [7]_. -- -[1] https://gcc.gnu.org/onlinedocs/gccint/Plugins.html -[2] https://gcc.gnu.org/onlinedocs/gccint/Plugin-API.html#Plugin-API -[3] https://gcc.gnu.org/onlinedocs/gccint/GIMPLE.html -[4] https://gcc.gnu.org/onlinedocs/gccint/IPA.html -[5] https://gcc.gnu.org/onlinedocs/gccint/RTL.html -[6] https://grsecurity.net/ -[7] https://pax.grsecurity.net/ +.. [1] https://gcc.gnu.org/onlinedocs/gccint/Plugins.html +.. [2] https://gcc.gnu.org/onlinedocs/gccint/Plugin-API.html#Plugin-API +.. [3] https://gcc.gnu.org/onlinedocs/gccint/GIMPLE.html +.. [4] https://gcc.gnu.org/onlinedocs/gccint/IPA.html +.. [5] https://gcc.gnu.org/onlinedocs/gccint/RTL.html +.. [6] https://grsecurity.net/ +.. [7] https://pax.grsecurity.net/ -2. Files -======== -$(src)/scripts/gcc-plugins +Files +===== + +**$(src)/scripts/gcc-plugins** + This is the directory of the GCC plugins. -$(src)/scripts/gcc-plugins/gcc-common.h +**$(src)/scripts/gcc-plugins/gcc-common.h** + This is a compatibility header for GCC plugins. It should be always included instead of individual gcc headers. -$(src)/scripts/gcc-plugin.sh +**$(src)/scripts/gcc-plugin.sh** + This script checks the availability of the included headers in gcc-common.h and chooses the proper host compiler to build the plugins (gcc-4.7 can be built by either gcc or g++). -$(src)/scripts/gcc-plugins/gcc-generate-gimple-pass.h -$(src)/scripts/gcc-plugins/gcc-generate-ipa-pass.h -$(src)/scripts/gcc-plugins/gcc-generate-simple_ipa-pass.h -$(src)/scripts/gcc-plugins/gcc-generate-rtl-pass.h +**$(src)/scripts/gcc-plugins/gcc-generate-gimple-pass.h, +$(src)/scripts/gcc-plugins/gcc-generate-ipa-pass.h, +$(src)/scripts/gcc-plugins/gcc-generate-simple_ipa-pass.h, +$(src)/scripts/gcc-plugins/gcc-generate-rtl-pass.h** + These headers automatically generate the registration structures for GIMPLE, SIMPLE_IPA, IPA and RTL passes. They support all gcc versions from 4.5 to 6.0. They should be preferred to creating the structures by hand. -3. Usage -======== +Usage +===== You must install the gcc plugin headers for your gcc version, -e.g., on Ubuntu for gcc-4.9: +e.g., on Ubuntu for gcc-4.9:: apt-get install gcc-4.9-plugin-dev -Enable a GCC plugin based feature in the kernel config: +Enable a GCC plugin based feature in the kernel config:: CONFIG_GCC_PLUGIN_CYC_COMPLEXITY = y -To compile only the plugin(s): +To compile only the plugin(s):: make gcc-plugins -- 2.9.4
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| From | Kees Cook <keescook@chromium.org> |
|---|---|
| Date | 2017-06-19 21:00 +0200 |
| Subject | Re: [PATCH v2 22/31] gcc-plugins.txt: standardize document format |
| Message-ID | <tUa43-6pD-69@gated-at.bofh.it> |
| In reply to | #1668358 |
On Sat, Jun 17, 2017 at 8:25 AM, Mauro Carvalho Chehab <mchehab@s-opensource.com> wrote: > Each text file under Documentation follows a different > format. Some doesn't even have titles! > > Change its representation to follow the adopted standard, > using ReST markups for it to be parseable by Sphinx: > > - promote main title; > - use the right markup for footnotes; > - use bold markup for files name; > - identify literal blocks; > - add blank lines to avoid Sphinx to complain; > - remove numeration from titles. > > Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com> Thanks! This should maybe get moved/indexed in dev-tools/. What do you think? Regardless: Acked-by: Kees Cook <keescook@chromium.org> -Kees -- Kees Cook Pixel Security
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