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

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Date:   Wed, 3 Oct 2018 14:13:53 +0200
From:   Giulio Benetti <giulio.benetti@...ronovasrl.com>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     Maxime Ripard <maxime.ripard@...tlin.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        David Airlie <airlied@...ux.ie>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH 1/2] drm/sun4i: tcon: fix check of tcon->panel null
 pointer

Il 03/10/2018 11:43, Chen-Yu Tsai ha scritto:
> On Wed, Oct 3, 2018 at 5:59 AM Giulio Benetti
> <giulio.benetti@...ronovasrl.com> 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.
> 
> There's actually more than one occurance of this error:
> 
> drivers/gpu/drm/sun4i/sun4i_lvds.c:     if (!IS_ERR(tcon->panel)) {
> drivers/gpu/drm/sun4i/sun4i_lvds.c:     if (!IS_ERR(tcon->panel)) {
> drivers/gpu/drm/sun4i/sun4i_rgb.c:      if (!IS_ERR(tcon->panel)) {
> drivers/gpu/drm/sun4i/sun4i_rgb.c:      if (!IS_ERR(tcon->panel)) {
> 
> These four are responsible for enabling and disabling the panel.
> 
> drivers/gpu/drm/sun4i/sun4i_tcon.c:     if (!IS_ERR(tcon->panel)) {
> 
> All this looks like it was left over from commit ebc9446135671 ("drm: convert
> drivers to use drm_of_find_panel_or_bridge"). We have checks against tcon->panel
> in several places and not all of them were converted.
> 

Then, I'm going to send a patchset to correct them.

Best regards
-- 
Giulio Benetti
CTO

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