linux-kernel - Re: [PATCH] drm/mxsfb: fix missing rollback on failure in mxsfb

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Message-ID: <468c6352-3301-4f0b-a2d4-d6a013417a0e@suse.de>
Date: Thu, 13 Mar 2025 15:40:43 +0100
From: Thomas Zimmermann <tzimmermann@...e.de>
To: Luca Ceresoli <luca.ceresoli@...tlin.com>, Marek Vasut <marex@...x.de>,
 Stefan Agner <stefan@...er.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Shawn Guo <shawnguo@...nel.org>,
 Sascha Hauer <s.hauer@...gutronix.de>,
 Pengutronix Kernel Team <kernel@...gutronix.de>,
 Fabio Estevam <festevam@...il.com>,
 Dario Binacchi <dario.binacchi@...rulasolutions.com>,
 Michael Trimarchi <michael@...rulasolutions.com>
Cc: Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
 dri-devel@...ts.freedesktop.org, imx@...ts.linux.dev,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/mxsfb: fix missing rollback on failure in
 mxsfb_probe()

Hi

Am 13.03.25 um 15:25 schrieb Luca Ceresoli:
> When aperture_remove_all_conflicting_devices() fails, the current code
> returns without going through the rollback actions at the end of the
> function, thus the actions done by drm_dev_alloc() and mxsfb_load() are not
> undone.
>
> Fix by using a goto statament, as done for the previous and following error
> conditions.
>
> Fixes: c8e7b185d45b ("drm/mxsfb: Remove generic DRM drivers in probe function")
> Signed-off-by: Luca Ceresoli <luca.ceresoli@...tlin.com>
> ---
> The offending commit is not yet merged into master, and even less in a
> released kernel, so this does not need to go through stable.
> ---
>   drivers/gpu/drm/mxsfb/mxsfb_drv.c | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> index c183b1112bc4e9fe4f3b048a2b6e4c98d1d47cb3..b4273e678d26dbc3dee2014266d61470da4e8010 100644
> --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> @@ -365,9 +365,10 @@ static int mxsfb_probe(struct platform_device *pdev)
>   	 * located anywhere in RAM
>   	 */
>   	ret = aperture_remove_all_conflicting_devices(mxsfb_driver.name);
> -	if (ret)
> -		return dev_err_probe(&pdev->dev, ret,
> -				     "can't kick out existing framebuffers\n");
> +	if (ret) {
> +		dev_err_probe(&pdev->dev, ret, "can't kick out existing framebuffers\n");
> +		goto err_unload;
> +	}

I must have missed that when I reviewed the patch. But this call should 
happen much earlier. right at the top of the probe function before 
drm_dev_alloc(). Conflicting drivers need to be kicked out before 
setting up DRM. Could you please send a patch to move the call to the 
top? No extra cleanup would be required then.

Best regards
Thomas

>   
>   	ret = drm_dev_register(drm, 0);
>   	if (ret)
>
> ---
> base-commit: f9f087d946266bc5da7c3a17bd8fd9d01969e3cf
> change-id: 20250313-mxsfb_probe-fix-rollback-on-error-3074b9080f34
>
> Best regards,

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)