linux-kernel - Re: [RFC PATCH] drm/ssd130x: Allocate buffer in the CRTC's .atomic

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Message-ID: <87ledqbah2.fsf@minerva.mail-host-address-is-not-set>
Date:   Fri, 01 Sep 2023 09:48:09 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Thomas Zimmermann <tzimmermann@...e.de>,
        linux-kernel@...r.kernel.org
Cc:     Maxime Ripard <mripard@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        dri-devel@...ts.freedesktop.org
Subject: Re: [RFC PATCH] drm/ssd130x: Allocate buffer in the CRTC's
 .atomic_check() callback

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

> Hi Javier,
>
> another idea about this patch: why not just keep the allocation in the 
> plane's atomic check, but store the temporary buffers in a plane struct. 
> You'd only grow the arrays length in atomic_check and later fetch the 
> pointers in atomic_update. It needs some locking, but nothing complicated.
>

Yes, that would work too. Another option is to just move the buffers to
struct ssd130x_device as it was before commit 45b58669e532 ("drm/ssd130x:
Allocate buffer in the plane's .atomic_check() callback") but just make
them fixed arrays with the size of the biggest format.

That will be some memory wasted but will prevent the problem of trying to
allocate buffers after drm_atomic_helper_swap_state() has been called.

> Best regards
> Thomas
>
> Am 30.08.23 um 08:25 schrieb Javier Martinez Canillas:

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat