Re: [alsa-devel] [PATCH] ASoC: sgtl5000: Use devm_ functions

[Lars-Peter Clausen <lars@metafoo.de>]

On 07/07/2014 05:23 PM, Julia Lawall wrote:
>
>
> On Mon, 7 Jul 2014, Fabio Estevam wrote:
>
>> On Mon, Jul 7, 2014 at 11:58 AM, Julia Lawall <julia.lawall@lip6.fr> wrote:
>>
>>> Nevertheless, there is already a call to devm_regulator_bulk_get in
>>> sgtl5000_enable_regulators which calls sgtl5000_replace_vddd_with_ldo
>>> which calls ldo_regulator_register.  That call was introduced by
>>>
>>> commit 63e54cd9caa3ce03635810608519e2b37d8bc706
>>> Author: Fabio Estevam <fabio.estevam@freescale.com>
>>> Date:   Thu Apr 24 14:13:08 2014 -0300
>>>
>>> It seems that that patch should be reverted?
>>
>> I think so. Russell also reported a kernel oops when unbinding this
>> module, so I will prepare a patch reverting it.
>
> There is documentation about what kinds of devm functions exist, but it is
> too bad that there is no documentation about where they can be used.
> Often there are several levels of function pointers involved, so it can be
> hard to figure out whether they can be used just by looking at the code.
> I have only taken the strategy of using them in kinds of functions where
> someone else has alreadyy figured out that they can be used.

Yes, it is probably a bit underdocumented. The rule of thumb is don't use it 
anywhere else except for device probe callbacks (and functions that are only 
called from a device probe function) and only for the device that is being 
probed. There are probably a couple of instances in the kernel where the 
manged resource allocators are used in places where they shouldn't be used.

- Lars