Re: [PATCH v2 2/4] platform/x86: thinkpad_acpi: Support for trackpoint doubletap

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 4/18/24 2:24 PM, Mark Pearson wrote:
> Hi Hans,
> 
> On Thu, Apr 18, 2024, at 7:34 AM, Hans de Goede wrote:
>> Hi Mark,
>>
>> On 4/18/24 1:57 AM, Mark Pearson wrote:
>>> Hi Hans,
>>>
>>> On Wed, Apr 17, 2024, at 4:06 PM, Hans de Goede wrote:
>>>> Hi Mark,
>>>>
>>>> On 4/17/24 9:39 PM, Hans de Goede wrote:
>>>>> Hi Mark,
>>>>>
>>>>> Thank you for the new version of this series, overall this looks good,
>>>>> one small remark below.
>>>>>
>>>>> On 4/17/24 7:31 PM, Mark Pearson wrote:
>>>>>> Lenovo trackpoints are adding the ability to generate a doubletap event.
>>>>>> This handles the doubletap event and sends the KEY_PROG1 event to
>>>>>> userspace.
>>>>>>
>>>>>> Signed-off-by: Mark Pearson <mpearson-lenovo@squebb.ca>
>>>>>> Signed-off-by: Vishnu Sankar <vishnuocv@gmail.com>
>>>>>> ---
>>>>>> Changes in v2:
>>>>>>  - Use KEY_PROG1 instead of KEY_DOUBLETAP as input maintainer doesn't
>>>>>>    want new un-specific key codes added.
>>>>>>  - Add doubletap to hotkey scan code table and use existing hotkey
>>>>>>    functionality.
>>>>>>  - Tested using evtest, and then gnome settings to configure a custom shortcut
>>>>>>    to launch an application.
>>>>>>
>>>>>>  drivers/platform/x86/thinkpad_acpi.c | 18 ++++++++++++++++++
>>>>>>  1 file changed, 18 insertions(+)
>>>>>>
>>>>>> diff --git a/drivers/platform/x86/thinkpad_acpi.c b/drivers/platform/x86/thinkpad_acpi.c
>>>>>> index 3b48d893280f..6d04d45e8d45 100644
>>>>>> --- a/drivers/platform/x86/thinkpad_acpi.c
>>>>>> +++ b/drivers/platform/x86/thinkpad_acpi.c
>>>>>> @@ -232,6 +232,9 @@ enum tpacpi_hkey_event_t {
>>>>>>  
>>>>>>  	/* Misc */
>>>>>>  	TP_HKEY_EV_RFKILL_CHANGED	= 0x7000, /* rfkill switch changed */
>>>>>> +
>>>>>> +	/* Misc2 */
>>>>>> +	TP_HKEY_EV_TRACK_DOUBLETAP      = 0x8036, /* trackpoint doubletap */
>>>>>>  };
>>>>>>  
>>>>>>  /****************************************************************************
>>>>>> @@ -1786,6 +1789,7 @@ enum {	/* hot key scan codes (derived from ACPI DSDT) */
>>>>>>  	TP_ACPI_HOTKEYSCAN_NOTIFICATION_CENTER,
>>>>>>  	TP_ACPI_HOTKEYSCAN_PICKUP_PHONE,
>>>>>>  	TP_ACPI_HOTKEYSCAN_HANGUP_PHONE,
>>>>>
>>>>> I understand why you've done this but I think this needs a comment,
>>>>> something like:
>>>>>
>>>>>         /*
>>>>>          * For TP_HKEY_EV_TRACK_DOUBLETAP, unlike the codes above which map to:
>>>>>          * (hkey_event - 0x1300) + TP_ACPI_HOTKEYSCAN_EXTENDED_START, this is
>>>>>          * hardcoded for TP_HKEY_EV_TRACK_DOUBLETAP handling. Therefor this must
>>>>>          * always be the last entry (after any 0x1300-0x13ff entries).
>>>>>          */
>>>>> +	TP_ACPI_HOTKEYSCAN_DOUBLETAP,
>>>>
>>>> Ugh, actually this will not work becuuse we want hotkeyscancodes to be stable
>>>> because these are userspace API since they can be remapped using hwdb so we
>>>> cannot have the hotkeyscancode changing when new 0x1300-0x13ff range entries
>>>> get added.
>>>>
>>>> So we need to either grow the table a lot and reserve a whole bunch of space
>>>> for future 0x13xx - 0x13ff codes or maybe something like this:
>>>>
>>>> diff --git a/drivers/platform/x86/thinkpad_acpi.c 
>>>> b/drivers/platform/x86/thinkpad_acpi.c
>>>> index 771aaa7ae4cf..af3279889ecc 100644
>>>> --- a/drivers/platform/x86/thinkpad_acpi.c
>>>> +++ b/drivers/platform/x86/thinkpad_acpi.c
>>>> @@ -1742,7 +1742,12 @@ enum {	/* hot key scan codes (derived from ACPI 
>>>> DSDT) */
>>>>  	TP_ACPI_HOTKEYSCAN_VOLUMEDOWN,
>>>>  	TP_ACPI_HOTKEYSCAN_MUTE,
>>>>  	TP_ACPI_HOTKEYSCAN_THINKPAD,
>>>> -	TP_ACPI_HOTKEYSCAN_UNK1,
>>>> +	/*
>>>> +	 * Note this gets send both on 0x1019 and on 
>>>> TP_HKEY_EV_TRACK_DOUBLETAP
>>>> +	 * hotkey-events. 0x1019 events have never been seen on any actual hw
>>>> +	 * and a scancode is needed for the special 0x8036 doubletap 
>>>> hotkey-event.
>>>> +	 */
>>>> +	TP_ACPI_HOTKEYSCAN_DOUBLETAP,
>>>>  	TP_ACPI_HOTKEYSCAN_UNK2,
>>>>  	TP_ACPI_HOTKEYSCAN_UNK3,
>>>>  	TP_ACPI_HOTKEYSCAN_UNK4,
>>>>
>>>> or just hardcode KEY_PROG1 like your previous patch does, but I'm not
>>>> a fan of that because of loosing hwdb remapping functionality for this
>>>> "key" then.
>>>>
>>>> Note I'm open to other suggestions.
>>>>
>>> Oh...I hadn't thought of that impact. That's not great :(
>>>
>>> I have an idea, but want to prototype it to see if it works out or not. Will update once I've had a chance to play with it.
>>
>> Thinking more about this I just realized that the input subsystem
>> already has a mechanism for dealing with scancode ranges with
>> (big) holes in them in the form of linux/input/sparse-keymap.h .
>>
>> I think that what needs to be done is convert the existing code
>> to use sparse-keymap, keeping the mapping of the "MHKP"
>> returned hkey codes to internal TP_ACPI_HOTKEYSCAN_* values
>> for currently supported "MHKP" hkey codes for compatibility
>> and then for new codes just directly map them in the sparse map
>> aka the struct key_entry table. After converting the existing code
>> to use sparse-keymap, then for the new events we would simply add:
>>
>>
>> 	{ KE_KEY, 0x131d, { KEY_VENDOR} }, /* Fn + N, system debug info */
>> 	{ KE_KEY, 0x8036, { KEY_PROG1 } }, /* Trackpoint doubletap */
>>
>> entries to the table without needing to define intermediate
>> TP_ACPI_HOTKEYSCAN_* values for these.
>>
> 
> Ah! I didn't know about sparse-keymap but it looks similar to what I was thinking and played with a bit last night. Agreed using existing infrastructure is better.
> 
> Only things I'd flag is that:
>  - It did look like it would be useful to identify keys that the driver handles (there aren't many but a few). Maybe one of the other key types can help handle that?
>  - There are also some keys that use the tpacpi_input_send_key_masked that might need some special consideration.
> 
>> I already have somewhat of a design for this in my head and I really
>> believe this is the way forward as it uses existing kernel infra
>> and it will avoid hitting this problem again when some other new
>> "MHKP" hkey codes show up.
>>
>> I plan to start working on implementing conversion of the existing
>> code to use sparse-keymap, which should result in a nice cleanup
>> after lunch and I hope to have something for you to test no later
>> then next Tuesday.
>>
> 
> That would be amazing - do let me know if there is anything I can help with. Agreed this will help clean up a bunch of the keycode handling :)

I noticed a small problem while working on this. The hwdb shipped with
systemd has:

# thinkpad_acpi driver
evdev:name:ThinkPad Extra Buttons:dmi:bvn*:bvr*:bd*:svnIBM*:pn*:*
 KEYBOARD_KEY_01=battery                                # Fn+F2
 KEYBOARD_KEY_02=screenlock                             # Fn+F3
 KEYBOARD_KEY_03=sleep                                  # Fn+F4
 KEYBOARD_KEY_04=wlan                                   # Fn+F5
 KEYBOARD_KEY_06=switchvideomode                        # Fn+F7
 KEYBOARD_KEY_07=zoom                                   # Fn+F8 screen expand
 KEYBOARD_KEY_08=f24                                    # Fn+F9 undock
 KEYBOARD_KEY_0b=suspend                                # Fn+F12
 KEYBOARD_KEY_0f=brightnessup                           # Fn+Home
 KEYBOARD_KEY_10=brightnessdown                         # Fn+End
 KEYBOARD_KEY_11=kbdillumtoggle                         # Fn+PgUp - ThinkLight
 KEYBOARD_KEY_13=zoom                                   # Fn+Space
 KEYBOARD_KEY_14=volumeup
 KEYBOARD_KEY_15=volumedown
 KEYBOARD_KEY_16=mute
 KEYBOARD_KEY_17=prog1                                  # ThinkPad/ThinkVantage button (high k

Notice the last line, this last line maps the old thinkpad /
thinkvantage key: https://www.thinkwiki.org/wiki/ThinkPad_Button
which is define by the kernel as KEY_VENDOR to KEY_PROG1 to
use a keycode below 240 for X11 compatiblity which does not
handle higher keycodes.

This means that in practice at least on older models
KEY_PROG1 is already taken and the thinkpad / thinkvantage key
does the same (open lenovo help center / sysinfo) as
what the new Fn + N key combo does. So it does makes sense
to map Fn + N to KEY_VENDOR so those align but given the existing
remapping of the thinkpad / thinkvantage key to PROG1 I think
it would be better to not use PROG1 for the doubletap.

I guess we can just use PROG2 instead to avoid the overlap
with the remapped old ThinkPad / ThinkVantage buttons
(which are more like Fn + N then doubletap).

Regards,

Hans