linux-kernel - Re: [PATCH v2] Revert "drm/fb-helper: improve DRM fbdev emulation device names"

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Date:   Sat, 4 Dec 2021 13:41:13 +0100
From:   Johannes Stezenbach <js@...21.net>
To:     Javier Martinez Canillas <javierm@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Daniel Vetter <daniel@...ll.ch>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>, David Airlie <airlied@...ux.ie>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v2] Revert "drm/fb-helper: improve DRM fbdev emulation
 device names"

Hi,

On Wed, Oct 20, 2021 at 06:57:40PM +0200, Javier Martinez Canillas wrote:
> This reverts commit b3484d2b03e4c940a9598aa841a52d69729c582a.
> 
> That change attempted to improve the DRM drivers fbdev emulation device
> names to avoid having confusing names like "simpledrmdrmfb" in /proc/fb.
> 
> But unfortunately, there are user-space programs such as pm-utils that
> match against the fbdev names and so broke after the mentioned commit.
> 
> Since the names in /proc/fb are used by tools that consider it an uAPI,
> let's restore the old names even when this lead to silly names like the
> one mentioned above.

I would like to ask about the fate of this patch. It doesn't
seem to have been picked up by anyone, does it?


Thanks,
Johannes


> Fixes: b3484d2b03e4 ("drm/fb-helper: improve DRM fbdev emulation device names")
> Reported-by: Johannes Stezenbach <js@...21.net>
> Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
> Reviewed-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
> ---
> 
> Changes in v2:
> - Add a comment explaining that the current /proc/fb names are an uAPI.
> - Add a Fixes: tag so it can be cherry-picked by stable kernels.
> - Add Ville Syrjälä's Reviewed-by tag.
> 
>  drivers/gpu/drm/drm_fb_helper.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 8e7a124d6c5a..22bf690910b2 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -1743,7 +1743,13 @@ void drm_fb_helper_fill_info(struct fb_info *info,
>  			       sizes->fb_width, sizes->fb_height);
>  
>  	info->par = fb_helper;
> -	snprintf(info->fix.id, sizeof(info->fix.id), "%s",
> +	/*
> +	 * The DRM drivers fbdev emulation device name can be confusing if the
> +	 * driver name also has a "drm" suffix on it. Leading to names such as
> +	 * "simpledrmdrmfb" in /proc/fb. Unfortunately, it's an uAPI and can't
> +	 * be changed due user-space tools (e.g: pm-utils) matching against it.
> +	 */
> +	snprintf(info->fix.id, sizeof(info->fix.id), "%sdrmfb",
>  		 fb_helper->dev->driver->name);
>  
>  }
> -- 
> 2.31.1
> 
>