Messages in this thread | | | Date | Thu, 04 Dec 2014 10:42:55 +0100 | From | Jacek Anaszewski <> | Subject | Re: [PATCH/RFC v9 02/19] Documentation: leds: Add description of LED Flash class extension |
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Hi Sakari,
Thanks for the review.
On 12/03/2014 06:08 PM, Sakari Ailus wrote: > Hi Jacek, > > On Wed, Dec 03, 2014 at 05:06:37PM +0100, Jacek Anaszewski wrote: >> The documentation being added contains overall description of the >> LED Flash Class and the related sysfs attributes. >> >> Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com> >> Acked-by: Kyungmin Park <kyungmin.park@samsung.com> >> Cc: Bryan Wu <cooloney@gmail.com> >> Cc: Richard Purdie <rpurdie@rpsys.net> >> --- >> Documentation/leds/leds-class-flash.txt | 50 +++++++++++++++++++++++++++++++ >> 1 file changed, 50 insertions(+) >> create mode 100644 Documentation/leds/leds-class-flash.txt >> >> diff --git a/Documentation/leds/leds-class-flash.txt b/Documentation/leds/leds-class-flash.txt >> new file mode 100644 >> index 0000000..82e58b1 >> --- /dev/null >> +++ b/Documentation/leds/leds-class-flash.txt >> @@ -0,0 +1,50 @@ >> + >> +Flash LED handling under Linux >> +============================== >> + >> +Some LED devices support two modes - torch and flash. The modes are >> +supported by the LED class (see Documentation/leds/leds-class.txt) >> +and LED Flash class respectively. >> + >> +In order to enable support for flash LEDs CONFIG_LEDS_CLASS_FLASH symbol >> +must be defined in the kernel config. A flash LED driver must register >> +in the LED subsystem with led_classdev_flash_register to gain flash >> +capabilities. >> + >> +Following sysfs attributes are exposed for controlling flash led devices: >> + >> + - flash_brightness - flash LED brightness in microamperes (RW) >> + - max_flash_brightness - maximum available flash LED brightness (RO) >> + - flash_timeout - flash strobe duration in microseconds (RW) >> + - max_flash_timeout - maximum available flash strobe duration (RO) >> + - flash_strobe - flash strobe state (RW) >> + - flash_sync_strobe - one flash device can control more than one >> + sub-led; when this atrribute is set to 1 > > s/atrribute/attribute/ > >> + the flash led will be strobed synchronously >> + with the other one controlled by the same >> + device; flash timeout setting is inherited >> + from the led being strobed explicitly and >> + flash brightness setting of a sub-led's >> + being synchronized is used (RW) > > The flash brightness shouldn't be determined by the strobed LED. If this is > a property of the hardware, then be it, but in general no, it it shouldn't > be an interface requirement. I think this should just say that the strobe is > synchronised.
I intended this to sound exactly as you laid it out above, but maybe it is obscure English. "and flash brightness setting of a sub-led >>>being synchronized<<< is used" - from my point of view the led being synchronized is the one that isn't strobed explicitly. But I'm ok with confining ourselves only to saying that strobe is synchronized.
> How does the user btw. figure out which flash LEDs may be strobed > synchronously using the LED flash interface?
The flash_sync_strobe argument is absent if synchronized strobe is not available for a LED. The driver defines this by setting newly added LED_DEV_CAP_COMPOUND flag.
Best Regards, Jacek Anaszewski
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