Re: [PATCH 4/5] media: i2c: cat24c208: driver for the cat24c208 EDID EEPROM

[Hans Verkuil <hverkuil-cisco@xs4all.nl>]

On 8/2/22 14:26, Andy Shevchenko wrote:
> On Tue, Aug 2, 2022 at 2:23 PM Andy Shevchenko
> <andy.shevchenko@gmail.com> wrote:
>> On Tue, Aug 2, 2022 at 2:21 PM Andy Shevchenko
>> <andy.shevchenko@gmail.com> wrote:
> 
> ...
> 
>>> You are blaming the wrong man here, i.e. devm. The problem as I stated
>>> above is developers who do not understand (pay attention to) the
>>> lifetime of the objects.
>>
>> That said, the devm has nothing to do with the driver still being
>> problematic for the scenario you described, no?
> 
> And the cleanest (at the first glance) solution is to make v4l2 to fix
> this bug by suppressing unbind attributes when the device is opened
> for all v4l2 subdev drivers, and restore it back when it's closed.
> 

Why would we do that? The patch works in the scenario that I described:
the memory is freed in the struct video_device release() callback, which
is called when the last reference to the video node goes away. This is
standard V4L2 framework behavior that works great in the case of a unbind.

Without devm_kzalloc it works fine, even when unbind is called. With
devm_kzalloc the unbind attributes would have to be suppressed. I see no
reason for that as media maintainer.

Regards,

	Hans