Messages in this thread | | | Subject | Re: [PATCH 1/2] platform/x86: asus-wmi: Call new led hw_changed API on kbd brightness change | From | Hans de Goede <> | Date | Tue, 5 Jun 2018 09:35:04 +0200 |
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Hi,
On 05-06-18 04:31, Darren Hart wrote: > On Mon, Jun 04, 2018 at 04:23:04PM +0200, Hans de Goede wrote: >> Hi, >> >> On 04-06-18 15:51, Daniel Drake wrote: >>> On Mon, Jun 4, 2018 at 7:22 AM, Hans de Goede <hdegoede@redhat.com> wrote: >>>> Is this really a case of the hardware itself processing the >>>> keypress and then changing the brightness *itself* ? >>>> >>>> From the "[PATCH 2/2] platform/x86: asus-wmi: Add keyboard backlight >>>> toggle support" patch I get the impression that the driver is >>>> modifying the brightness from within the kernel rather then the >>>> keyboard controller are ACPI embeddec-controller doing it itself. >>>> >>>> If that is the case then the right fix is for the driver to stop >>>> mucking with the brighness itself, it should simply report the >>>> right keyboard events and export a led interface and then userspace >>>> will do the right thing (and be able to offer flexible policies >>>> to the user). >>> >>> Before this modification, the driver reports the brightness keypresses >>> to userspace and then userspace can respond by changing the brightness >>> level, as you describe. >>> >>> You are right in that the hardware doesn't change the brightness >>> directly itself, which is the normal usage of LED_BRIGHT_HW_CHANGED. >>> >>> However this approach was suggested by Benjamin Berg and Bastien >>> Nocera in the thread: Re: [PATCH v2] platform/x86: asus-wmi: Add >>> keyboard backlight toggle support >>> https://marc.info/?l=linux-kernel&m=152639169210655&w=2 >>> >>> The issue is that we need to support a new "keyboard backlight >>> brightness cycle" key (in the patch that follows this one) which >>> doesn't fit into any definitions of keys recognised by the kernel and >>> likewise there's no userspace code to handle it. >>> >>> If preferred we could leave the standard brightness keys behaving as >>> they are (input events) and make the new special key type directly >>> handled by the kernel? >> >> I'm sorry that Benjamin and Bastien steered you in this direction, >> IMHO none of it should be handled in the kernel. >> >> Anytime any sort of input is directly responded to by the kernel >> it is a huge PITA to deal with from userspace. The kernel will have >> a simplistic implementation which almost always is wrong. >> >> Benjamin, remember the pain we went through with rfkill hotkey >> presses being handled in the kernel ? >> >> And then there is the whole acpi_video.brightness_switch_enabled >> debacle, which is an option which defaults to true which causes >> the kernel to handle LCD brightness key presses, which all distros >> have been patching to default to off for ages. >> >> To give a concrete example, we may want to implement software >> dimming / auto-off of the kbd backlight when the no keys are >> touched for x seconds. This would seriously get in the way of that. >> >> So sorry, but NACK to this series. > > So if instead of modifying the LED value, the kernel platform drivers > converted the TOGGLE into a cycle even by converting to an UP event > based on awareness of the plaform specific max value and the read > current value, leaving userspace to act on the TOGGLE/UP events - would > that be preferable?
I was thinking about doing that as a workaround myself, but I'm not sure that is a good idea (because of e.g. races with userspace auto-correcting the brightness based on ambient light and/or keyboard activity).
As I see it there are 2 proper solutions to this:
1) Make userspace treat KEY_KBDILLUMTOGGLE as a cycle key, this is what the kbd-backlight on most laptops with a single hotkey (*) does in cases where this is handled in firmware, rather then left to the OS. The handled in firmware is the case which I created the led_classdev_notify_brightness_hw_changed() API for. This would be my preferred solution and I believe that Benjamin is discussing this with Bastien ATM.
2) Add a new KEY_KBDILLUMCYCLE event and send that for the TOGGLE code on these laptops.
Regards,
Hans
*) Rather then separate up / down hotkeys
> > Something like: > > if (code == TOGGLE && ledval < ledmax) > code = UP; > > sparse_keymap_report_event(..., code, ...) > > } >
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