Re: [PATCH 1/2] Input: soc_button_array - Set input device name

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Mon, Jan 23, 2017 at 02:10:44PM -0800, Dmitry Torokhov wrote:
> On Sun, Jan 22, 2017 at 11:10:31AM +0100, Hans de Goede wrote:
> > Hi,
> > 
> > On 22-01-17 11:00, Dmitry Torokhov wrote:
> > >On Sun, Jan 22, 2017 at 12:49 AM, Hans de Goede <hdegoede@redhat.com> wrote:
> > >>Hi,
> > >>
> > >>On 21-01-17 20:13, Dmitry Torokhov wrote:
> > >>>
> > >>>On Mon, Jan 09, 2017 at 06:57:06PM +0100, Hans de Goede wrote:
> > >>>>
> > >>>>On some tablets using the soc_button_array driver the buttons do not
> > >>>>follow the standard home, power, volume_up, volume_down, rotation_lock
> > >>>>button order as published by Microsoft.
> > >>>>
> > >>>>We can use the existing udev hwdb mechanism to fix this up, but then
> > >>>>the created devices must have a unique name, therefor this commit adds
> > >>>>a unique name for the 2 created gpio-keys input devices.
> > >>>
> > >>>
> > >>>Why does it have to have unique name? You should be able to match on
> > >>>other input device properties, for example ATTR{capabilities/ev} or
> > >>>ATTR{capabilities/keys} to identify the device you want to adjust.
> > >>
> > >>
> > >>hwdb entries do not have access to full udev data, basically there
> > >>are 2 match formats:
> > >>
> > >># Supported hardware matches are:
> > >>#  - Generic input devices match:
> > >>#      evdev:input:bZZZZvYYYYpXXXXeWWWW-VVVV
> > >>#    This matches on the kernel modalias of the input-device, mainly:
> > >>#    ZZZZ is the bus-id (see /usr/include/linux/input.h BUS_*), YYYY, XXXX
> > >>and
> > >>#    WWW are the 4-digit hex uppercase vendor, product and version ID and
> > >>VVVV
> > >>#    is an arbitrary length input-modalias describing the device
> > >>capabilities.
> > >>#    The vendor, product and version ID for a device node "eventX" is listed
> > >>#    in /sys/class/input/eventX/device/id.
> > >>#
> > >>#  - Input driver device name and DMI data match:
> > >>#      evdev:name:<input device name>:dmi:bvn*:bvr*:bd*:svn<vendor>:pn*
> > >>#    <input device name> is the name device specified by the
> > >>#    driver, <vendor> is the firmware-provided string exported
> > >>#    by the kernel DMI modalias, see /sys/class/dmi/id/modalias
> > >>
> > >>
> > >>Since we want to match on DMI info we need to use the second, and
> > >>the info you are referring to is not available here.
> > >
> > >Well, you can either teach hwdb new tricks or mangle the name in udev
> > >rule. As far as I can see the original invocation is:
> > >
> > ># device matching the input device name and the machine's DMI data
> > >KERNELS=="input*", IMPORT{builtin}="hwdb
> > >'evdev:name:$attr{name}:$attr{[dmi/id]modalias}'", \
> > > RUN{builtin}+="keyboard", GOTO="evdev_end"
> > >
> > >You can add a similar rule that also looks at ATTR{whatever}, but
> > >instead of using "name:$attr{name}" you can use whatever string you
> > >want.
> > >
> > >There is no need to change kernel, it already exports all necessary data.
> > 
> > Ah, come one, requiring a custom udev rule for this is a pain, where as
> 
> OK, do not require custom property. Provide an extended one:
> 
> # device matching the input device properties and the machine's DMI data
> KERNELS=="input*", IMPORT{builtin}="hwdb
> 'evdev:name:$attr{name}:phys:$attr{phys}:ev:$attr{capabilities/ev}:$attr{[dmi/id]modalias}'", \
>   RUN{builtin}+="keyboard"
> 
> and either migrate old keymaps to the extended one, or keep both. In the
> end, there is nothing special in 'evdev:name:...' prefix, it matches
> across all lines of hwdb with whatever is provided in the rule.
> 
> > this is really easy to fix on the kernel side.
> 
> Even if changing the kernel seems most convenient for you it does not
> mean it is the right approach.
> 
> > 
> > Besides that, the way soc_button_array works is that we currently end
> > up with 2 identical named (gpio_keys) input devices which is all sorts
> > of inconvenient, e.g. during testing the setkeycode support I had
> > to guess which was which when invoking evemu-record to test, they
> > will have the same name in "xinput list", etc.
> > 
> > Input device names really should be unique where ever possible, for
> > various reasons, and here we can easily make them unique.
> 
> We never provided any guarantees about uniqueness of names of input
> devices and I do not think we should start now. If you plug 2 same USB
> keyboards you'll get 2 devices with same names. Same goes for mice,
> tablets, etc. I do not see why SOC buttons should be different.

Forgot to add: for ordinary users, distinction between between
autorepeat and not-autorepeat SOC buttons devices is absolutely
uninteresting. They could care less. You just want something different
about them to trigger hwdb match, and we already have that, but not in
name.

Thanks.

-- 
Dmitry