On 01/26/2017 08:51 PM, Jacek Anaszewski wrote: > On 01/26/2017 09:33 AM, Pali Rohár wrote: >> On Wednesday 25 January 2017 22:35:53 Jacek Anaszewski wrote: >>> On 01/25/2017 05:49 PM, Pali Rohár wrote: >>>> On Wednesday 25 January 2017 17:11:27 Hans de Goede wrote: >>>>> Some LEDs may have their brightness level changed autonomously >>>>> (outside of kernel control) by hardware / firmware. This commit >>>>> adds support for an optional brightness_hw_changed attribute to >>>>> signal such changes to userspace (if a driver can detect them): >>>>> >>>>> What: /sys/class/leds/<led>/brightness_hw_changed >>>>> Date: January 2017 >>>>> KernelVersion: 4.11 >>>>> Description: >>>>> Last hardware set brightness level for this LED. Some LEDs >>>>> may be changed autonomously by hardware/firmware. Only LEDs >>>>> where this happens and the driver can detect this, will >>>>> have this file. >>>>> >>>>> This file supports poll() to detect when the hardware >>>>> changes the brightness. >>>>> >>>>> Reading this file will return the last brightness level set >>>>> by the hardware, this may be different from the current >>>>> brightness. >> >> In which situation this attribute may be different? >> >> I think some information should be present in this description... > > The first sentence in description says: > > "Last hardware set brightness level for this LED" - i.e. it may be > different from the _actual_ brightness, which could have been set by > LED class driver. > >>>>> Drivers which want to support this, simply add LED_BRIGHT_HW_CHANGED to >>>>> their flags field and call led_classdev_notify_brightness_hw_changed() >>>>> with the hardware set brightness when they detect a hardware / firmware >>>>> triggered brightness change. >>>>> >>>>> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx> >>>> >>>> Just speculation: What about using name 'actual_brightness'? It provides >>>> same output on read as actual_brightness from /sys/class/backlight/. >>> >>> This name is ambiguous. Propagating it to the LED subsystem only because >>> it exists in backlight is not sufficient argument IMHO. >> >> I thought that having same name could help userspace and also to have >> consistency between similar subsystems. But ok, that was just my >> speculation. > > Please also note the "actual" would be ambiguous especially in view > of my above explanation. > >> I have just one small suggestion in current name "brightness_hw_changed". >> As it provides regular read() capability I would suggest to not indicate >> "activity" (changed) in name... > > Without "changed" one could think that brightness file (the one we have > currently) doesn't reflect hardware state. A new, possibly better name has just come to my mind. Since the file has two purposes: to notify about brightness changes made by hardware and caching last such a change, then we could call it hw_brightness_cache. Now there is no activity in the file name. -- Best regards, Jacek Anaszewski
