linux-kernel - RE: [PATCH 3/3] platform/x86: dell-wmi: add keys to bios_to_linux

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Message-ID: <8baab72e3d2e407792c3ffa1d9fffba8@AUSX13MPC105.AMER.DELL.COM>
Date:   Mon, 8 Jun 2020 15:46:44 +0000
From:   <Mario.Limonciello@...l.com>
To:     <pali@...nel.org>, <y.linux@...itcher.com>
CC:     <linux-kernel@...r.kernel.org>,
        <platform-driver-x86@...r.kernel.org>, <mjg59@...f.ucam.org>
Subject: RE: [PATCH 3/3] platform/x86: dell-wmi: add keys to
 bios_to_linux_keycode

> -----Original Message-----
> From: platform-driver-x86-owner@...r.kernel.org <platform-driver-x86-
> owner@...r.kernel.org> On Behalf Of Pali Rohár
> Sent: Monday, June 8, 2020 4:00 AM
> To: Y Paritcher
> Cc: linux-kernel@...r.kernel.org; platform-driver-x86@...r.kernel.org;
> Matthew Garrett
> Subject: Re: [PATCH 3/3] platform/x86: dell-wmi: add keys to
> bios_to_linux_keycode
> 
> 
> [EXTERNAL EMAIL]
> 
> Hello!
> 
> On Monday 08 June 2020 00:22:26 Y Paritcher wrote:
> > Increase length of bios_to_linux_keycode to 2 bytes to allow for a new
> > keycode 0xffff, this silences the following messages being logged at
> > startup on a Dell Inspiron 5593

Which event type?  Can you show the whole WMI buffer that came through?

> >
> > dell_wmi: firmware scancode 0x48 maps to unrecognized keycode 0xffff
> > dell_wmi: firmware scancode 0x50 maps to unrecognized keycode 0xffff
> >
> > Signed-off-by: Y Paritcher <y.linux@...itcher.com>
> > ---
> >  drivers/platform/x86/dell-wmi.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/platform/x86/dell-wmi.c b/drivers/platform/x86/dell-
> wmi.c
> > index f37e7e9093c2..5ef716e3034f 100644
> > --- a/drivers/platform/x86/dell-wmi.c
> > +++ b/drivers/platform/x86/dell-wmi.c
> > @@ -196,7 +196,7 @@ struct dell_dmi_results {
> >  };
> >
> >  /* Uninitialized entries here are KEY_RESERVED == 0. */
> > -static const u16 bios_to_linux_keycode[256] = {
> > +static const u16 bios_to_linux_keycode[65536] = {
> 
> This change dramatically increase memory usage. I guess other that
> maintainers would not like such change.
> 
> >  	[0]	= KEY_MEDIA,
> >  	[1]	= KEY_NEXTSONG,
> >  	[2]	= KEY_PLAYPAUSE,
> > @@ -237,6 +237,7 @@ static const u16 bios_to_linux_keycode[256] = {
> >  	[37]	= KEY_UNKNOWN,
> >  	[38]	= KEY_MICMUTE,
> >  	[255]	= KEY_PROG3,
> > +	[65535]	= KEY_UNKNOWN,
> 
> Also it seems that this change is not complete. It looks like that you
> map two different scancodes (0x48 and 0x50) to same keycodes, moreover
> both are unknown.
> 
> Could you please describe which key presses (or events) generate
> delivering these WMI scancode events?
> 
> Note that purpose of printing unknown/unrecognized keys messages is to
> inform that current pressed key was not processed or that it was
> ignored.
> 
> For me it looks like this just just hide information that key was not
> processed correctly as this change does not implement correct processing
> of this key.
> 
> Also, could you share documentation about these 0x48/0x50 events? Or it
> is under NDA?
> 
> >  };
> >
> >  /*
> > --
> > 2.27.0
> >

I would actually question if there is value to lines in dell-wmi.c like this:

pr_info("Unknown WMI event type 0x%x\n", (int)buffer_entry[1]);

and

pr_info("Unknown key with type 0x%04x and code 0x%04x pressed\n", type, code);

In both of those cases the information doesn't actually help the user, by default it's
ignored by the driver anyway.  It just notifies the user it's something the driver doesn't
comprehend.  I would think these are better suited to downgrade to debug.  And if
a key combination isn't doing something expected the user can use dyndbg to turn it
back on and can be debugged what should be populated or "explicitly" ignored.