Re: [PATCH] drm/ssd130x: Fix an oops when attempting to update a disabled plane

[Javier Martinez Canillas]

Javier Martinez Canillas <javierm@xxxxxxxxxx> writes:

> Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> writes:
>
> Hello Geert and Thomas,
>
>> Hi Thomas,
>>
>> On Mon, Jul 17, 2023 at 10:48 AM Thomas Zimmermann <tzimmermann@xxxxxxx> wrote:
>
> [...]
>
>>>
>>> After some discussion on IRC, I'd suggest to allocate the buffer
>>> somewhere within probe. So it will always be there when the plane code runs.
>>>
>>> A full fix would be to allocate the buffer memory as part of the plane
>>> state and/or the plane's atomic_check. That's a bit more complicated if
>>> you want to shared the buffer memory across plane updates.
>>
>> Note that actually two buffers are involved: data_array (monochrome,
>> needed for each update), and buffer (R8, only needed when converting
>> from XR24 to R1).
>>
>> For the former, I agree, as it's always needed.
>> For the latter, I'm afraid it would set a bad example: while allocating
>> a possibly-unused buffer doesn't hurt for small displays, it would
>> mean wasting 1 MiB in e.g. the repaper driver (once it has gained
>> support for R1 ;^).
>>
>
> Maybe another option is to allocate on the struct drm_mode_config_funcs
> .fb_create callback? That way, we can get the mode_cmd->pixel_format and
> determine if only "data_array" buffer must be allocated or also "buffer".
>

Something like the following patch: