linux-kernel - RE: [PATCH v2 3/3] platform/x86: dell-wmi: add new dmi keys to bios_to_linux

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Message-ID: <a8b5465e4c834f1c98c8499acb0cacb7@AUSX13MPC105.AMER.DELL.COM>
Date:   Fri, 12 Jun 2020 14:59:39 +0000
From:   <Mario.Limonciello@...l.com>
To:     <pali@...nel.org>
CC:     <rdunlap@...radead.org>, <y.linux@...itcher.com>,
        <linux-kernel@...r.kernel.org>,
        <platform-driver-x86@...r.kernel.org>, <mjg59@...f.ucam.org>
Subject: RE: [PATCH v2 3/3] platform/x86: dell-wmi: add new dmi keys to
 bios_to_linux_keycode

> >
> > >
> > > And what does mean "no function"? I do not know what should I imagine
> if
> > > I receive key press marked as "no function".
> >
> > It means no action is expected to occur, should behave like a no-op.  I
> think
> > discarding it makes fine sense.
> 
> Thank you! This was missing bit of information.
> 
> Just I'm curious, why firmware sends "no-op" event which we could ignore?
> :D
> 

I don't have details on this, but I can at least hypothesize a situation that
there was a manufacturing error with the wrong keyboard applied.  Like think if
the system has keyboard without a backlight and there was a keyboard with
a silkscreened key for modifying backlight.  In this case firmware events
related to keyboard backlight shouldn't flow through so firmware could instead
send this type of event.

> I can imagine that those events / scan codes may contain some
> information which we can use...

I mean I suppose you can choose to ignore my comments, but I'm telling you this
event doesn't contain anything useful.

> 
> > >
> > > > > E.g. I remember that pressing Fn+Q or Fn+W on some Dell Latitude
> > > > > generates code 255, which could prove my thesis about "special
> codes"
> > > > > (which are probably not found in e.g. Windows or Linux mapping
> tables).
> > > > >
> > > > > > >  };
> > > > > > >
> > > > > > >  /*
> > > > > > > @@ -503,10 +504,7 @@ static void handle_dmi_entry(const struct
> > > > > dmi_header *dm, void *opaque)
> > > > > > >  					&table->keymap[i];
> > > > > > >
> > > > > > >  		/* Uninitialized entries are 0 aka KEY_RESERVED. */
> > > > > > > -		u16 keycode = (bios_entry->keycode <
> > > > > > > -			       ARRAY_SIZE(bios_to_linux_keycode)) ?
> > > > > > > -			bios_to_linux_keycode[bios_entry->keycode] :
> > > > > > > -			KEY_RESERVED;
> > > > > > > +		u16 keycode = bios_to_linux_keycode[bios_entry-
> >keycode];
> > > > > > >
> > > > > > >  		/*
> > > > > > >  		 * Log if we find an entry in the DMI table that we
> don't
> > > > > > >
> > > > > >
> > > > > > Something like:
> > > > > >
> > > > > > 		u16 keycode;
> > > > > >
> > > > > > 		keycode = bios_entry->keycode == 0xffff ? KEY_UNKNOWN :
> > > > > > 			(bios_entry->keycode <
> > > > > > 			       ARRAY_SIZE(bios_to_linux_keycode)) ?
> > > > > > 			bios_to_linux_keycode[bios_entry->keycode] :
> > > > > > 			KEY_RESERVED;
> > > > > >
> > > > > >
> > > > > >
> > > > > > Also please fix this:
> > > > > > (no To-header on input) <>
> > > > >
> > > > > Hint: specifying git send-email with '--to' argument instead of '--
> cc'
> > > > > should help.
> > > > >
> > > > > >
> > > > > > --
> > > > > > ~Randy
> > > > > >