linux-kernel - Re: [PATCH v4] platform/x86: dell-laptop: Fix bogus keyboard backlight sysfs interface

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Message-ID: <CAHp75Vc+9X5LKnoaO=Q3UGqH4Ok-pBxKpgE5zFSpcX_1e9v2=A@mail.gmail.com>
Date:   Tue, 20 Jun 2017 20:25:36 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     Pali Rohár <pali.rohar@...il.com>,
        Andy Shevchenko <andy@...radead.org>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        "dvhart@...radead.org" <dvhart@...radead.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] platform/x86: dell-laptop: Fix bogus keyboard
 backlight sysfs interface

On Tue, Jun 20, 2017 at 6:05 AM, Kai-Heng Feng
<kai.heng.feng@...onical.com> wrote:
> Dell Latitude 3160 does not have keyboard backlight, but there is a
> sysfs interface for it, which does nothing at all.
>
> KBD_LED_ON_TOKEN is the only token can be found. Since it doesn't have
> KBD_LED_OFF_TOKEN or KBD_LED_AUTO_*_TOKEN, it should be safe to assume
> at least two tokens should be present to support keyboard backlight.
> Not all models have ON token - they may have multiple AUTO tokens instead.
>
> Models which do not use SMBIOS token to control keyboard backlight, also
> have this issue. Brightness level is 0 on these models. Verified on Dell
> Inspiron 3565.
>
> Reports keyboard backlight is supported only when at least two modes are
> present.
>

Pushed to testing, thanks!

> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> ---
>
> v4:
> Change commit log - not all models have ON token.
>
> v3:
> Change the logic, there should be at least two modes present to claim it
> supports backlight. Suggested by Pali Rohár.
>
> v2:
> The only token can be found is actually KBD_LED_ON_TOKEN, which is BIT(5),
> instead of KBD_LED_OFF_TOKEN. Change commit log accordingly.
>
> Use token bit to make the intention more clear.
> Also consider kbd_mode_levels_count and kbd_info.levels, suggested by
> Pali Rohár.
>
> Use XOR to simplify the bitmask comparison, suggested by
> Andy Shevchenko.
>
>  drivers/platform/x86/dell-laptop.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c
> index ec202094bd50..f42159fd2031 100644
> --- a/drivers/platform/x86/dell-laptop.c
> +++ b/drivers/platform/x86/dell-laptop.c
> @@ -1510,7 +1510,11 @@ static void kbd_init(void)
>         ret = kbd_init_info();
>         kbd_init_tokens();
>
> -       if (kbd_token_bits != 0 || ret == 0)
> +       /*
> +        * Only supports keyboard backlight when it has at least two modes.
> +        */
> +       if ((ret == 0 && (kbd_info.levels != 0 || kbd_mode_levels_count >= 2))
> +           || kbd_get_valid_token_counts() >= 2)
>                 kbd_led_present = true;
>  }
>
> --
> 2.13.1
>



-- 
With Best Regards,
Andy Shevchenko