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

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Date:   Fri, 16 Jun 2017 17:46:58 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Pali Rohár <pali.rohar@...il.com>
Cc:     mjg59@...f.ucam.org, dvhart@...radead.org,
        platform-driver-x86@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] platform/x86: dell-laptop: Fix bogus keyboard backlight
 sysfs interface

On Fri, Jun 16, 2017 at 3:52 PM, Pali Rohár <pali.rohar@...il.com> wrote:
> Should not this check to be rather:
>
> (kbd_token_bits != 0 && (kbd_token_bits & BIT(KBD_LED_OFF_TOKEN)) != BIT(KBD_LED_OFF_TOKEN))
>
> To express that we have at least one token at it is different from
> KBD_LED_OFF_TOKEN token?

Yes, this expresses the intention more clearly. I'll use it instead.

>
>>               kbd_led_present = true;
>>  }
>>
>
> And more important, there are three ways how to control keyboard
> backlight level:
>
> 1) Via SMBIOS token
> 2) Via SMBIOS call 4/11/0x2 (arg2, byte0)
> 3) Via SMBIOS call 4/11/0x2 (arg3, byte2)
>
> You are adding special case when only one SMBIOS toekn OFF is present
> which belongs to 1).
>
> Therefore there should be same check for 2) and 3) that there are more
> the one option to set...

I am not familiar with SMBIOS call.
Can you point out where 2) and 3) functions are?

>
> --
> Pali Rohár
> pali.rohar@...il.com