linux-kernel - Re: [FIXED][PATCH] dell-laptop: Fix backlight detection

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Message-ID: <CAHp75VcUJ70dtNcGfuJbo473ddOJ4_RdgcNsk_sVE5uVeHf_4Q@mail.gmail.com>
Date:   Wed, 18 Jul 2018 13:23:12 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Damien Thébault <damien@...o.net>
Cc:     Darren Hart <dvhart@...radead.org>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        Pali Rohár <pali.rohar@...il.com>,
        Andy Shevchenko <andy@...radead.org>,
        Mario Limonciello <mario.limonciello@...l.com>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [FIXED][PATCH] dell-laptop: Fix backlight detection

On Wed, Jul 18, 2018 at 1:06 PM, Damien Thébault <damien@...o.net> wrote:
> Fix return code check for "max brightness" ACPI call.
>
> The dell laptop ACPI video brightness control is not present on dell
> laptops anymore, but was present in older kernel versions.
>
> The code that checks the return value is incorrect since the SMM
> refactoring.
>
> The old code was:
>   if (buffer->output[0] == 0)
>
> Which was changed to:
>   ret = dell_send_request(...)
>   if (ret)
>
> However, dell_send_request() will return 0 if buffer->output[0] == 0,
> so we must change the check to:
>   if (ret == 0)
>
> This issue was found on a Dell M4800 laptop, and the fix tested on it
> as well.
>

I have pushed this to my review and testing queue, thanks!

But I'm going to push this to Linus this week since it's definitely
stable material.

> Fixes: 549b4930f057 ("dell-smbios: Introduce dispatcher for SMM calls")
> Signed-off-by: Damien Thébault <damien@...o.net>
> Tested-by: Damien Thébault <damien@...o.net>
> Reviewed-by: Pali Rohár <pali.rohar@...il.com>
> Reviewed-by: Mario Limonciello <mario.limonciello@...l.com>
> ---
>  drivers/platform/x86/dell-laptop.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c
> index f1fa8612db40..06978c14c83b 100644
> --- a/drivers/platform/x86/dell-laptop.c
> +++ b/drivers/platform/x86/dell-laptop.c
> @@ -2185,7 +2185,7 @@ static int __init dell_init(void)
>                 dell_fill_request(&buffer, token->location, 0, 0, 0);
>                 ret = dell_send_request(&buffer,
>                                         CLASS_TOKEN_READ, SELECT_TOKEN_AC);
> -               if (ret)
> +               if (ret == 0)
>                         max_intensity = buffer.output[3];
>         }
>
> --
> 2.18.0
>



-- 
With Best Regards,
Andy Shevchenko