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Re: [LKP] [lkp] [gpio] 3c702e9987: kmsg.user_verbs:couldn't_register_device_number

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  Re: [LKP] [lkp] [gpio] 3c702e9987: kmsg.user_verbs:couldn't_register_device_number "Huang\, Ying" <ying.huang@intel.com> - 2016-02-15 03:40 +0100
    Re: [LKP] [lkp] [gpio] 3c702e9987: kmsg.user_verbs:couldn't_register_device_number Linus Walleij <linus.walleij@linaro.org> - 2016-02-15 10:40 +0100

#1334109 — Re: [LKP] [lkp] [gpio] 3c702e9987: kmsg.user_verbs:couldn't_register_device_number

Michael Welling <mwelling@ieee.org> writes:

> On Sun, Feb 14, 2016 at 02:59:06PM +0800, kernel test robot wrote:
>> FYI, we noticed the below changes on
>> 
>> https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio.git chardev
>> commit 3c702e9987e261042a07e43460a8148be254412e ("gpio: add a userspace chardev ABI for GPIOs")
>> 
>> 
>> [    1.951191] user_verbs: couldn't register device number
>
> Looks like user_verbs is using a static device node setup.
>
> enum {
>         IB_UVERBS_MAJOR       = 231,
>         IB_UVERBS_BASE_MINOR  = 192,
>         IB_UVERBS_MAX_DEVICES = 32
> };
>
> #define IB_UVERBS_BASE_DEV      MKDEV(IB_UVERBS_MAJOR, IB_UVERBS_BASE_MINOR)
>
> Something tells me that a new GPIO chardev is taking this spot.
>
> It looks like the device is documented to be using the range:
> https://www.kernel.org/doc/Documentation/devices.txt
>
> Could you run cat /proc/devices?
>

Sorry, the test mechanism is not flexible enough to run some shell
command in test system.  Could you provide a specialized debug kernel to
dump the necessary information in kernel log?  We can collect dmesg
easily.

Best Regards,
Huang, Ying

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#1334323

On Mon, Feb 15, 2016 at 3:39 AM, Huang, Ying <ying.huang@intel.com> wrote:
> Michael Welling <mwelling@ieee.org> writes:

>> Could you run cat /proc/devices?
>
> Sorry, the test mechanism is not flexible enough to run some shell
> command in test system.  Could you provide a specialized debug kernel to
> dump the necessary information in kernel log?  We can collect dmesg
> easily.

Can you try this:

diff --git a/fs/char_dev.c b/fs/char_dev.c
index 24b142569ca9..74a2d433273e 100644
--- a/fs/char_dev.c
+++ b/fs/char_dev.c
@@ -96,6 +96,8 @@ __register_chrdev_region(unsigned int major,
unsigned int baseminor,
             goto out;
         }
         major = i;
+        pr_info("CHARDEV: allocate major %d for \"%s\"\n",
+            i, name);
     }

     cd->major = major;

Then dmesg |grep CHARDEV should tell what we need to know.

Yours,
Linus Walleij

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