linux-kernel - Re: [PATCH v2 1/3] drm: Remove superfluous arg when calling to drm_fbdev_generic

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Date:   Mon, 2 May 2022 19:15:16 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     linux-kernel@...r.kernel.org,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        dri-devel@...ts.freedesktop.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v2 1/3] drm: Remove superfluous arg when calling to
 drm_fbdev_generic_setup()

On 5/2/22 18:55, Javier Martinez Canillas wrote:

[snip]

> 
>> drop the depth option to drm_fbdev_generic_setup() ? There's a FIXME
>> comment in drm_fbdev_generic_setup() that could be related.
>>
> 
> A FIXME makes sense, I'll add that to when posting a v3.

There's actually a FIXME already in drm_fbdev_generic_setup(), so it's
a documented issue [0]:

void drm_fbdev_generic_setup(struct drm_device *dev,
			     unsigned int preferred_bpp)
{
...
	/*
	 * FIXME: This mixes up depth with bpp, which results in a glorious
	 * mess, resulting in some drivers picking wrong fbdev defaults and
	 * others wrong preferred_depth defaults.
	 */
	if (!preferred_bpp)
		preferred_bpp = dev->mode_config.preferred_depth;
	if (!preferred_bpp)
		preferred_bpp = 32;
	fb_helper->preferred_bpp = preferred_bpp;
...
}

[0]: https://elixir.bootlin.com/linux/v5.18-rc5/source/drivers/gpu/drm/drm_fb_helper.c#L2553

-- 
Best regards,

Javier Martinez Canillas
Linux Engineering
Red Hat