linux-kernel - Re: [PATCH] input: i8042: add quirk to implement i8042 detect for AMD

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Date:	Sat, 17 Oct 2015 09:38:47 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Wan ZongShun <mcuos.com@...il.com>, Huang Rui <ray.huang@....com>,
	Vincent Wan <Vincent.Wan@....com>, linux-input@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] input: i8042: add quirk to implement i8042 detect for AMD

On Fri, Oct 16, 2015 at 12:21:55PM +0200, Borislav Petkov wrote:
> On Fri, Oct 16, 2015 at 05:35:40PM +0800, Wan ZongShun wrote:
> > 2015-10-16 16:58 GMT+08:00 Borislav Petkov <bp@...en8.de>:
> > > On Fri, Oct 16, 2015 at 09:27:00AM -0400, Vincent Wan wrote:
> > >> Detecting platform supports i8042 or not, AMD resorted to
> > >> BIOS's FADT i8042 flag.
> > >>
> > >> Signed-off-by: Vincent Wan <Vincent.Wan@....com>
> > >> ---
> > >>  drivers/input/serio/i8042-x86ia64io.h | 6 ++++++
> > >>  1 file changed, 6 insertions(+)
> > 
> > >>  /*
> > >> @@ -1047,6 +1048,11 @@ static int __init i8042_platform_init(void)
> > >>       /* Just return if pre-detection shows no i8042 controller exist */
> > >>       if (!x86_platform.i8042_detect())
> > >>               return -ENODEV;
> > >> +
> > >> +     if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
> > >
> > > Why the vendor check if you're accessing a bit defined in the ACPI spec?
> > 
> > From intel's 'x86_platform.i8042_detect' implementation, I doubt if
> > their BIOS is providing this i8024 flag.
> 
> Why would you doubt that - it is at least in ACPI v4, if not earlier. If
> you still doubt that, go and check it or ask Intel people.
> 
> > So I have to implement my codes carefully.
> 
> What are you people talking about?!
> 
> It is in the ACPI spec - this bit is either set or not. If it is not

Well, the fact that is is in a spec does not mean that vendors follow
it (and BTW I do not think that AMD as a CPU vendor can vouch for a
random notebook or desktop vendor that acquired and then hacked on some
version of some BIOS from some BIOS vendor so I agree that this check is
a no-go).

Historically we did not trust BIOS data with regard to i8042 on x86.
Maybe we should now using certain date cutoff (anything manufactured
past 201[2345?]).

Does Windows respect this flag? If it does then we could also trust it,
and not only on AMD but for all x86 CPUs.

Thanks.

-- 
Dmitry
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