linux-kernel - Re: [PATCH] macintosh: move mac

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Date:   Mon, 29 May 2017 20:03:25 +0200
From:   Michal Suchánek <msuchanek@...e.de>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org
Subject: Re: [PATCH] macintosh: move mac_hid driver to input/mouse.

On Sun, 28 May 2017 10:55:40 -0700
Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:

> On Sun, May 28, 2017 at 11:47:58AM +0200, Michal Suchanek wrote:
> > On Tue, 9 May 2017 17:43:27 -0700
> > Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:

> > 
> > If not then please do your job as maintainer and accept trivial
> > patches for perfectly working drivers we have now.  
> 
> I am doing my job as a maintainer right now. The driver might have
> been beneficial 15 years ago, when we did not have better options,
> but I would rather not continue expanding it's use.
> 
> The main problem with the driver is that the functionality it is not
> easily discoverable by end users. And once you plumb it through
> userspace to present users with options you might as well handle it
> all in userspace.
> 
...
> 
> >   
> > > 
> > > What hardware do you believe would benefit from this and why?  
> > 
> > Any touchpad hardware where you cannot press two buttons at once to
> > emulate the third button due to hardware design. And any touchpad
> > hardware on which some of the buttons are broken when it comes to
> > it.
> > 
> > It is built into a notebook and works fine for moving the cursor but
> > due to lack of usable buttons you still need a mouse to use the
> > notebook.  
> 
> Have you tried simply redefining keymap of your keyboard to emit
> BTN_RIGHT/BTN_MIDDLE? Both atkbd and HID keyboards support keymap
> updates from userspace/udev/hwdb and if there is a driver that does
> not support it I will take patches fixing that.

How is that more easily discoverable by users?

More importantly how is that mapping supposed to be represented in a
hwdb file?

The help text in the hwdb file says:

# Scan codes are specified as:
#   KEYBOARD_KEY_<hex scan code>=<key code identifier>
# The scan code should be expressed in hex lowercase. The key codes
# are retrieved and normalized from the kernel input API header.

So they are converted in some unspecified way.

The example below defines some mappings, presumably:

evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer*:pn*
evdev:atkbd:dmi:bvn*:bvr*:bd*:svnGateway*:pnA0A1*:pvr*
evdev:atkbd:dmi:bvn*:bvr*:bd*:svneMachines:pneMachines*E725:pvr*
 KEYBOARD_KEY_a5=help                                   # Fn+F1
 KEYBOARD_KEY_a6=setup                                  # Fn+F2
 KEYBOARD_KEY_a7=battery                                # Fn+F3

/usr/include/linux/input-event-codes.h has occurence of battery in

#define KEY_BATTERY		236

meaning that the unspecified conversion is probably performed by

1) stripping KEY_ prefix
2) converting to lowercase

This is what systemd hwdb check script does in reverse when checking
the keycode values.

The BTN_LEFT 0x110 value does not conflict with KEY_* values, though.
So technically you could include it in the keymap. If you had a tool
for that. And if it is not rejected by the kernel. And if it does not
crash your X server which is very picky about receiving pointer events
from a keyboard or the other way around.

Thanks

Michal