On 12/04/2015 07:40 AM, Tolga Cakir wrote: > I think we need a decision about what needs to be done in kernel and what is better handled in user-space. I've walked through the Corsair Vengeance K90 driver (hid-corsair.c) and I must say, I'm not really happy about the desicions made in the design. In my opinion, we should only do essential stuff in kernel space and do the rest in user-space. > > To be more precise about hid-corsair.c (and possibly future gaming keyboard implementations): > > 1. We should not handle profile switching and exposing a sysfs ABI for profile-number in kernel-space. This has no advantage over keeping track of profiles in user-space. We need to use user-space programs anyway in order to handle macros and profile-sensitive key-handling. Using a keyboard specific ABI for parsing the profile just adds complexity to kernel- and user-space. > > 2. We should not map false keycodes to keys. hid-corsair.c is using BTN_TRIGGER_HAPPY[N] - this is a huge design flaw in my opinion. Eventhough this might get the job done, I'm questioning the design decision. First of all, we're generally talking about KEYs on a keyboard, not BTNs. Second, they are not TRIGGERs. Third, they are not HAPPY. Also, BTN_TRIGGER_HAPPY[N] is only specified for up to 40 extra keys. What do we do with gaming keyboards, which offer more? The Microsoft Sidewinder X6 has 33 non-standard extra keys for example (agreed, it's less than 40, but still near the maximum). Do we really need to map random linux/input.h keycodes to non-standard keys? I choose the TRIGGER_HAPPY buttons because the only use I found for it was extra buttons on some devices. It seems the most appropriate. It would be nice to have special key codes for this kind of keys, I asked about that with my original patch but I did not get any answer so the BTN_TRIGGER_HAPPY stayed there. They are keys the user may be interested in, I don't see why they should not have key events. > > I think mapping linux/input.h keycodes to non-standard keys has only one reason: to keep things simple with X11. As Clement mentioned, keycodes above 256 don't work with X11. However, this should not be a reason to hack workarounds into kernel. We can use hidraw / hiddev in user-space instead to catch those events and map them accordingly to our needs (they are designed to be fully programmable keys after all). This adds complexity in user-space, but also adds flexibility and we don't need to break / workaround any HID stuff. It does not work with X11 but it works with existing remapping software based on evdev. I don't understand what you mean with "break / workaround", I am remapping *invalid* HID usage code from the keyboard. If I don't do that pressing those keys triggers unwanted key events. > > 3. We should either have common ABI for gaming keyboards or we shouldn't have them at all (or just in very special cases). This just adds complexity in kernel- and user-space, as lots of keyboards need to be handled their own way. Gaming keyboards have things in common, like LEDs. Creating an ABI for setting extra LEDs is totally legit, but we should define standards, so user-space applications can rely on something. Most keyboards have multiple profile LEDs, 1 recording LED, sometimes 1 gaming mode LED (disabling Windows key) and sometimes keyboard backlight is also adjustable. > > We could define a common ABI for them: > - read-only profile_led_count (or profile_led_max): parse number of profile_leds > - rw profile_led_[N]: setting and parsing profile_led_[N] status, 0 and 1 Isn't this the same as the current_profile attribute you were arguing against? > - rw recording_led: setting and parsing recording_led status, 0 and 1 > - rw gaming_led: setting and parsing gaming_led status, 0 and 1 > - read-only backlight_max: parse maximum brightness > - rw backlight: setting and parsing backlight intensity, 0 - backlight_max LED class devices already do that. > > Exposing a read-write interface for switching HW / SW mode is also a legit use-case for ABI. > > A major drawback of ABI (and user-space programs depending on it): we cannot respond fast enough to new devices, as people need to wait several months / years for the updated kernel versions or run a patched kernel (including all the drawbacks associated with using a custom kernel for the average user). Drivers can be added as out-of-tree modules. > > The kernel's role would be creating an interface to interact with the keyboard's extras and it's up to the user-space, how to make use of them (e.g. profile-switching macro tool using LEDs for active profile number, or custom script using them in a blinking pattern for incoming E-Mails). > > Now about the Logitech G710+. Things, that need and should be handled in kernel space (in my opinion): > > 1. Bugs. Thanks to Jimmy Berry, there is already a G710+ bugfix applied to 4.4 (http://www.spinics.net/lists/linux-input/msg42186.html). There are no other bugs for the G710+ I'm aware of. > > 2. The Logitech G710+ is a composite device: interface #1 is used for G1 - G6 keys + usual standard keyboard. Please note, that the G1 - G6 keys are outputting KEY_1 - KEY_6. Interface #2 is used for M1 - M3, MR key (macro recording and profile switching / LEDs) and also the G1 - G6 keys (outputting non-standard HID events!). As you can see, G1 - G6 keys are double mapped for 2 devices. In case, an operating system doesn't recognize G1 - G6 keys on interface #2, we're simply getting KEY_1 - KEY6 from interface #1. The Windows Logitech driver is sending out a specific packet, so the G1 - G6 keys on interface #1 get completely disabled (maybe other changes aswell, I don't know). This is a perfect use case for kernel-space. > > Sorry for the wall of text. > > Cheers, > Tolga -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
