Hi all,
Am 25.03.24 um 19:30 schrieb Hans de Goede:
[snip]
If the kernel already handles the custom protocol into generic HID, the
work for userspace is not too hard because they can deal with a known
protocol and can be cross-platform in their implementation.
I'm mentioning that cross-platform because SDL used to rely on the
input, LEDs, and other Linux peculiarities and eventually fell back on
using hidraw only because it's way more easier that way.
The other advantage of LampArray is that according to Microsoft's
document, new devices are going to support it out of the box, so they'll
be supported out of the box directly.
Most of the time my stance is "do not add new kernel API, you'll regret
it later". So in that case, given that we have a formally approved
standard, I would suggest to use it, and consider it your API.
The only new UAPI would be the use_leds_uapi switch to turn on/off the backwards compatibility.
Actually we don't even need that. Typically there is a single HID
driver handling both keys and the backlight, so userspace cannot
just unbind the HID driver since then the keys stop working.
But with a virtual LampArray HID device the only functionality
for an in kernel HID driver would be to export a basic keyboard
backlight control interface for simple non per key backlight control
to integrate nicely with e.g. GNOME's backlight control.
Don't forget that in the future there will be devices that natively support
LampArray in their firmware, so for them it is the same device.
Regards,
Werner
And then when OpenRGB wants to take over it can just unbind the HID
driver from the HID device using existing mechanisms for that.
Hmm, I wonder if that will not also kill hidraw support though ...
I guess getting hidraw support back might require then also manually
binding the default HID input driver. Bentiss any input on this?
Background info: as discussed earlier in the thread Werner would like
to have a basic driver registering a /sys/class/leds/foo::kbd_backlight/
device, since those are automatically supported by GNOME (and others)
and will give basic kbd backlight brightness control in the desktop
environment. This could be a simple HID driver for
the hid_allocate_device()-ed virtual HID device, but userspace needs
to be able to move that out of the way when it wants to take over
full control of the per key lighting.
Regards,
Hans
The control flow for the whole system would look something like this:
- System boots
- Kernel driver initializes keyboard (maybe stops rainbowpuke boot effects, sets brightness to a default value, or initializes a solid color)
- systemd-backlight restores last keyboard backlight brightness
- UPower sees sysfs leds entry and exposes it to DBus for DEs to do keyboard brightness handling
- If the user wants more control they (auto-)start OpenRGB
- OpenRGB disables sysfs leds entry via use_leds_uapi to prevent double control of the same device by UPower
- OpenRGB directly interacts with hidraw device via LampArray API to give fine granular control of the backlight
- When OpenRGB closes it should reenable the sysfs leds entry
- System shutdown
- Since OpenRGB reenables the sysfs leds entry, systemd-backlight can correctly store a brightness value for next boot
Regards,
Werner
Side note to self: I really need to resurrect the hidraw revoke series
so we could export those hidraw node to userspace with uaccess through
logind...
Cheers,
Benjamin
