linux-kernel - Re: [PATCH v2 1/2] drm/sun4i: tcon: fix check of tcon->panel null pointer

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Date:   Thu, 4 Oct 2018 21:54:06 +0200
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Giulio Benetti <giulio.benetti@...ronovasrl.com>
Cc:     David Airlie <airlied@...ux.ie>, Chen-Yu Tsai <wens@...e.org>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] drm/sun4i: tcon: fix check of tcon->panel null
 pointer

Hi,

On Wed, Oct 03, 2018 at 04:24:57PM +0200, Giulio Benetti wrote:
> At the moment, the check of tcon->panel to be valid is wrong. IS_ERR()
> has been used, but that macro doesn't check if tcon->panel pointer is
> null or not, but check if tcon->panel is between -1 and -4095(MAX_ERRNO).
> 
> Remove IS_ERR() from tcon->panel checking and let "if (tcon->panel)" as
> condition to check if it's a pointer not null.
> 
> Signed-off-by: Giulio Benetti <giulio.benetti@...ronovasrl.com>

The commit log should be improved. The issue isn't really with the
IS_ERR macro as you suggest, but that what is returned by
of_drm_find_panel, and thus stored in tcon->panel. is not an error
pointer in the first place but a NULL pointer on error. So the check
doesn't check for the proper thing.

Maxime

-- 
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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