linux-kernel - Re: [PATCH] platform/x86: dell-rbtn: Improve explanation about DELLABC6

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Message-ID: <CAHp75VeV0tKOFFxOC6n7htJLb_J_4JH8_wCk-G6LBRc9poVf8Q@mail.gmail.com>
Date:   Sat, 27 May 2017 19:27:19 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Darren Hart <dvhart@...radead.org>
Cc:     Platform Driver <platform-driver-x86@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Mario Limonciello <mario_limonciello@...l.com>,
        Pali Rohár <pali.rohar@...il.com>
Subject: Re: [PATCH] platform/x86: dell-rbtn: Improve explanation about DELLABC6

On Sat, May 27, 2017 at 8:16 AM, Darren Hart <dvhart@...radead.org> wrote:
> From: Andy Lutomirski <luto@...nel.org>
>
> According to Mario at Dell, the DELLABC6 device should not be used on a
> Linux system. It also conflicts with Intel-HID and its interactions with
> Network Manager. Document that we are aware of the device, but that we
> are intentionally ignoring it.
>

Pali made a good point.
Otherwise, FWIW:
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>

> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> [dvhart: New commit message and minor comment wording fixes]
> Cc: Mario Limonciello <mario_limonciello@...l.com>
> Cc: "Pali Rohár" <pali.rohar@...il.com>
> Signed-off-by: Darren Hart (VMware) <dvhart@...radead.org>
> ---
>  drivers/platform/x86/dell-rbtn.c | 26 +++++++++++++++++++-------
>  1 file changed, 19 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/platform/x86/dell-rbtn.c b/drivers/platform/x86/dell-rbtn.c
> index dcd9f40..2eeef03 100644
> --- a/drivers/platform/x86/dell-rbtn.c
> +++ b/drivers/platform/x86/dell-rbtn.c
> @@ -223,14 +223,26 @@ static const struct acpi_device_id rbtn_ids[] = {
>          * This driver can also handle the "DELLABC6" device that
>          * appears on the XPS 13 9350, but that device is disabled
>          * by the DSDT unless booted with acpi_osi="!Windows 2012"
> -        * acpi_osi="!Windows 2013".  Even if we boot that and bind
> -        * the driver, we seem to have inconsistent behavior in
> -        * which NetworkManager can get out of sync with the rfkill
> -        * state.
> +        * acpi_osi="!Windows 2013".
>          *
> -        * On the XPS 13 9350 and similar laptops, we're not supposed to
> -        * use DELLABC6 at all.  Instead, we handle the rfkill button
> -        * via the intel-hid driver.
> +        * According to Mario at Dell:
> +        *
> +        *  DELLABC6 is a custom interface that was created solely to
> +        *  have airplane mode support for Windows 7.  For Windows 10
> +        *  the proper interface is to use that which is handled by
> +        *  intel-hid.  A OEM airplane mode driver is not used.
> +        *
> +        *  Since the kernel doesn't identify as Windows 7 it would be
> +        *  incorrect to do attempt to use that interface.
> +        *
> +        * Even if we override _OSI and bind to DELLABC6, we end up
> +        * with inconsistent behavior in which NetworkManager can get
> +        * out of sync with the rfkill state.  This happens because
> +        * NetworkManager receives events from intel-hid and fights with
> +        * dell-rbtn for control.
> +        *
> +        * The upshot is that it's better to just ignore DELLABC6
> +        * devices.
>          */
>
>         { "", 0 },
> --
> 2.9.4
>



-- 
With Best Regards,
Andy Shevchenko