[PATCH v2] media: stm32: dcmi: Switch to __v4l2_subdev_state_alloc()

[Marek Vasut]

On 6/29/22 14:26, Tomi Valkeinen wrote:

[...]

>>> Perhaps the best way to solve this is just to remove the underscores
>>> from __v4l2_subdev_state_alloc, and change all the drivers which create
>>> temporary v4l2_subdev_states to use that (and the free) functions. And
>>> also create the helper macro which can be used in those cases where the
>>> call is simple (the state is not modified or accessed by the caller).
>>
>> As long as we prevent any new driver from using that API, that's fine
>> with me.
> 
> An alternative would be to keep the v4l2_subdev_state as a local 
> variable (allocated in the stack), and add a new function, 
> v4l2_subdev_state_local_init() or such. The function would initialize 
> the given state, expecting the allocatable fields to be already 
> allocated (state->pads, which in the above cases points to another local 
> variable, i.e. stack).
> 
> This would prevent the need of a free call, which, while not complex as 
> such, might cause a bigger amount of changes in some cases to handle the 
> error paths correctly.
> 
> Of course, if the above-mentioned macro works, then that's the easiest 
> solution. But that won't work for all drivers.

Don't you think a driver fix shouldn't involve "rework the subsystem" 
requirement to be applicable ?