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

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Date:   Mon, 17 Jul 2023 11:00:13 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Thomas Zimmermann <tzimmermann@...e.de>,
        linux-kernel@...r.kernel.org
Cc:     dri-devel@...ts.freedesktop.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH] drm/ssd130x: Fix an oops when attempting to update a
 disabled plane

Thomas Zimmermann <tzimmermann@...e.de> writes:

Hello Thomas,

> Hi
>
> Am 13.07.23 um 18:32 schrieb Javier Martinez Canillas:

[...]

>>   
>> +static const struct drm_mode_config_helper_funcs ssd130x_mode_config_helpers = {
>> +	.atomic_commit_tail = drm_atomic_helper_commit_tail_rpm,
>> +};
>> +
>
> 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.
>

Yes, that's also what Geert suggested so I'll just do that. And also make
it a dev managed resource.

> 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.
>

I don't think is worth the complexity, allocating it on probe and released
when the device is unbound from the driver should be enough as Geert said.

> Best regards
> Thomas
>
>

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat