linux-kernel - Re: [PATCH 1/1] drm/nouveau: fix error return code in nouveau_backlight

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Date:   Sat, 8 May 2021 09:34:00 +0200
From:   Pierre Moreau <pierre.morrow@...e.fr>
To:     Zhen Lei <thunder.leizhen@...wei.com>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        Ben Skeggs <bskeggs@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        nouveau <nouveau@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] drm/nouveau: fix error return code in
 nouveau_backlight_init()

Hello Zhen,

There was a similar patch sent in last month, though which does not seem to
have been merged yet; see
https://lists.freedesktop.org/archives/nouveau/2021-April/038451.html.

Whether `ret` should be `-ENOSPC` or `-ENOMEM` is hard to say as
`nouveau_get_backlight_name()` could fail due to either.

I will propose an alternative fix which modifies `nouveau_get_backlight_name()`
to return an int so the actual error code can be propagated back instead of
guessed, as well as fix an ida ID leak which I just spotted.

Best,
Pierre

On 2021-05-08 — 11:48, Zhen Lei wrote:
> Fix to return a negative error code from the error handling case instead
> of 0, as done elsewhere in this function.
> 
> Fixes: db1a0ae21461 ("drm/nouveau/bl: Assign different names to interfaces")
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> ---
>  drivers/gpu/drm/nouveau/nouveau_backlight.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c b/drivers/gpu/drm/nouveau/nouveau_backlight.c
> index 72f35a2babcb..097ca344a086 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_backlight.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c
> @@ -273,6 +273,7 @@ nouveau_backlight_init(struct drm_connector *connector)
>  		return -ENOMEM;
>  
>  	if (!nouveau_get_backlight_name(backlight_name, bl)) {
> +		ret = -ENOSPC;
>  		NV_ERROR(drm, "Failed to retrieve a unique name for the backlight interface\n");
>  		goto fail_alloc;
>  	}
> -- 
> 2.25.1
> 
>