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Re: [PATCHv2 1/4] staging: android: ion: Drop heap type masks

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Hi,

On Fri, Sep 02, 2016 at 12:36:25PM -0700, Laura Abbott wrote:
>On 09/02/2016 06:41 AM, Brian Starkey wrote:
>>Hi Laura,
>>
>>On Thu, Sep 01, 2016 at 03:40:41PM -0700, Laura Abbott wrote:
>>>
>>>There is no advantage to having heap types be a mask. The ion client has
>>>long since dropped the mask. Drop the notion of heap type masks as well.
>>>
>>
>>I know this is the same patch you sent last time, so sorry for not
>>picking this up then - but I'm curious what "The" ion client is here?
>>
>
>ion_client_create used to take a mask to indicate what heap types it
>could allocate from. This hasn't been the case since 2bb9f5034ec7
>("gpu: ion: Remove heapmask from client"). "The ion client" probably
>should have been "struct ion_client"

Ah I see, the in-kernel ion_client. Sorry, I completely forgot that
even existed (because it's totally useless - how is a driver meant to
find the global ion_device?)

>
>>Our ion client(s) certainly still use these masks, and it's still
>>used as a mask within ion itself - even if the relationship between a
>>mask and a heap type has been somewhat lost.
>
>Where is it used in Ion? I don't see it in tree unless I missed something
>and I'm not eager to keep this around for out of tree code. What's the
>actual use for this?

You're certainly right that these heap-ID-to-allocation-mask macros
are unused in the kernel, but I don't really see the reason for
removing them - they are convenient (for now).

Example: I'm using the dummy ion driver, and I want to allocate from
the SYSTEM_CONTIG heap - the ION_HEAP_SYSTEM_CONTIG_MASK gives me the
exact mask I need for that.

It seems your opinion is that heap-IDs are already, and should be,
completely decoupled from their type. That sounds like a good idea to
me, but it's not true (yet) - again check out the dummy driver.

At the moment, heap-IDs are assigned by ion drivers in any way they
see fit. For as long as that stays the case there's always going to
be heap-masks hard-coded in UAPI kernel headers (in-tree or not), so
removing these particular masks seems a bit fruitless.

I'd rather see driver-assigned heap-IDs disappear completely, and have
them assigned by ion core from an idr or something. At that point
these macros really *are* meaningless, and I'd be totally fine with
removing them (and userspace won't be able to depend on hard-coded
allocation masks any more - it will have to use the query ioctl,
which I assume is the whole point?).

IMO it's not the right time to remove these macros, because they still
have meaning and usefulness.

Cheers,
Brian

>
>>
>>Thanks,
>>Brian
>>
>>>Signed-off-by: Laura Abbott <labbott@redhat.com>
>>>---
>>>drivers/staging/android/uapi/ion.h | 6 ------
>>>1 file changed, 6 deletions(-)
>>>
>>>diff --git a/drivers/staging/android/uapi/ion.h b/drivers/staging/android/uapi/ion.h
>>>index 0a8e40f..a9c4e8b 100644
>>>--- a/drivers/staging/android/uapi/ion.h
>>>+++ b/drivers/staging/android/uapi/ion.h
>>>@@ -44,14 +44,8 @@ enum ion_heap_type {
>>>                   * must be last so device specific heaps always
>>>                   * are at the end of this enum
>>>                   */
>>>-    ION_NUM_HEAPS = 16,
>>>};
>>>
>>>-#define ION_HEAP_SYSTEM_MASK        (1 << ION_HEAP_TYPE_SYSTEM)
>>>-#define ION_HEAP_SYSTEM_CONTIG_MASK    (1 << ION_HEAP_TYPE_SYSTEM_CONTIG)
>>>-#define ION_HEAP_CARVEOUT_MASK        (1 << ION_HEAP_TYPE_CARVEOUT)
>>>-#define ION_HEAP_TYPE_DMA_MASK        (1 << ION_HEAP_TYPE_DMA)
>>>-
>>>#define ION_NUM_HEAP_IDS        (sizeof(unsigned int) * 8)
>>>
>>>/**
>>>--
>>>2.7.4
>>>
>

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[PATCHv2 0/4] New Ion ioctls Laura Abbott <labbott@redhat.com> - 2016-09-02 00:50 +0200
  [PATCHv2 4/4] staging: android: ion: Add ioctl to query available heaps Laura Abbott <labbott@redhat.com> - 2016-09-02 00:50 +0200
    Re: [PATCHv2 4/4] staging: android: ion: Add ioctl to query  available heaps Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-09-02 08:20 +0200
      Re: [PATCHv2 4/4] staging: android: ion: Add ioctl to query available  heaps Laura Abbott <labbott@redhat.com> - 2016-09-02 22:50 +0200
        Re: [PATCHv2 4/4] staging: android: ion: Add ioctl to query  available heaps Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-09-03 15:00 +0200
  [PATCHv2 1/4] staging: android: ion: Drop heap type masks Laura Abbott <labbott@redhat.com> - 2016-09-02 00:50 +0200
    Re: [PATCHv2 1/4] staging: android: ion: Drop heap type masks Brian Starkey <brian.starkey@arm.com> - 2016-09-02 15:50 +0200
      Re: [PATCHv2 1/4] staging: android: ion: Drop heap type masks Laura Abbott <labbott@redhat.com> - 2016-09-02 21:40 +0200
        Re: [PATCHv2 1/4] staging: android: ion: Drop heap type masks Brian Starkey <brian.starkey@arm.com> - 2016-09-05 13:30 +0200
          Re: [PATCHv2 1/4] staging: android: ion: Drop heap type masks Laura Abbott <labbott@redhat.com> - 2016-09-07 00:20 +0200
            Re: [PATCHv2 1/4] staging: android: ion: Drop heap type masks Brian Starkey <brian.starkey@arm.com> - 2016-09-07 11:00 +0200
  [PATCHv2 3/4] staging: android: ion: Add an ioctl for ABI checking Laura Abbott <labbott@redhat.com> - 2016-09-02 00:50 +0200
    Re: [PATCHv2 3/4] staging: android: ion: Add an ioctl for ABI  checking Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-09-02 08:20 +0200
      Re: [PATCHv2 3/4] staging: android: ion: Add an ioctl for ABI  checking Laura Abbott <labbott@redhat.com> - 2016-09-02 22:30 +0200
    Re: [Linaro-mm-sig] [PATCHv2 3/4] staging: android: ion: Add an ioctl for ABI checking Arnd Bergmann <arnd@arndb.de> - 2016-09-02 11:10 +0200
      Re: [Linaro-mm-sig] [PATCHv2 3/4] staging: android: ion: Add an ioctl  for ABI checking Laura Abbott <labbott@redhat.com> - 2016-09-02 22:40 +0200
        Re: [Linaro-mm-sig] [PATCHv2 3/4] staging: android: ion: Add an ioctl for ABI checking Arnd Bergmann <arnd@arndb.de> - 2016-09-02 23:40 +0200
          Re: [Linaro-mm-sig] [PATCHv2 3/4] staging: android: ion: Add an ioctl  for ABI checking Laura Abbott <labbott@redhat.com> - 2016-09-03 00:20 +0200
  [PATCHv2 2/4] staging: android: ion: Pull out ion ioctls to a separate file Laura Abbott <labbott@redhat.com> - 2016-09-02 00:50 +0200
    Re: [PATCHv2 2/4] staging: android: ion: Pull out ion ioctls to a  separate file Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-09-02 14:50 +0200
      Re: [PATCHv2 2/4] staging: android: ion: Pull out ion ioctls to a  separate file Laura Abbott <labbott@redhat.com> - 2016-09-02 22:00 +0200

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