linux-kernel - Re: [PATCH v2] backlight: gpio_backlight: Drop output gpio direction check for initial power state

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20230721084251.GF2525277@aspen.lan>
Date:   Fri, 21 Jul 2023 09:42:51 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Ying Liu <victor.liu@....com>
Cc:     "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "lee@...nel.org" <lee@...nel.org>,
        "jingoohan1@...il.com" <jingoohan1@...il.com>,
        "deller@....de" <deller@....de>,
        "andy@...nel.org" <andy@...nel.org>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "brgl@...ev.pl" <brgl@...ev.pl>
Subject: Re: [PATCH v2] backlight: gpio_backlight: Drop output gpio direction
 check for initial power state

On Fri, Jul 21, 2023 at 07:31:37AM +0000, Ying Liu wrote:
> If gpio pin is in input state but backlight is currently off due to
> default pull downs, then initial power state is set to FB_BLANK_UNBLANK
> in DT boot mode with phandle link and the backlight is effectively
> turned on in gpio_backlight_probe(), which is undesirable according to
> patch description of commit ec665b756e6f ("backlight: gpio-backlight:
> Correct initial power state handling").
>
> Quote:
> ---
> If in DT boot we have phandle link then leave the GPIO in a state which the
> bootloader left it and let the user of the backlight to configure it further.
> ---
>
> So, let's drop output gpio direction check and only check gpio value to set
> the initial power state.
>
> Signed-off-by: Liu Ying <victor.liu@....com>

Based on the discussion for v1 about 706dc68102bc ("backlight: gpio:
Explicitly set the direction of the GPIO"), I think there should
be a Fixes: tag here.


Daniel.