Hi Pavel,
Thanks for the review.
On 02/11/2015 10:57 PM, Pavel Machek wrote:
On Thu 2015-02-05 09:42:53, 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 <[email protected]>
Acked-by: Kyungmin Park <[email protected]>
Cc: Bryan Wu <[email protected]>
Cc: Richard Purdie <[email protected]>
---
Documentation/leds/leds-class-flash.txt | 63 +++++++++++++++++++++++++++++++
1 file changed, 63 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..16c6187
--- /dev/null
+++ b/Documentation/leds/leds-class-flash.txt
@@ -0,0 +1,63 @@
+
+Flash LED handling under Linux
+==============================
+
+Some LED devices support two modes - torch and flash. In the LED subsystem
+those modes are supported by LED class (see Documentation/leds/leds-class.txt)
+and LED Flash class respectively. The torch mode related features are enabled
+by default and the flash ones only if a driver declares it by setting
+LED_DEV_CAP_FLASH flag.
+
+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 function to gain flash
+related capabilities.
+
+There are flash LED devices which can control more than one LED and allow for
+strobing the sub-LEDs synchronously. A LED will be strobed synchronously with
+the one whose identifier is written to the flash_sync_strobe sysfs attribute.
+The list of available sub-LED identifiers can be read from the
available_sync_leds
+sysfs attribute. In order to enable the related settings the driver must set
+LED_DEV_CAP_SYNC_STROBE flag.
+
+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)
in microamperes
+ - flash_timeout - flash strobe duration in microseconds (RW)
+ - max_flash_timeout - maximum available flash strobe duration
(RO)
in microseconds
+ - flash_strobe - flash strobe state (RW)
This is integer..?
I can be 0 or 1. Let's make it more precise:
- flash_strobe - flash strobe state (RW):
semantics on write:
0: turn the flash LED off
1: strobe the flash LED
semantics on read:
0: flash LED is off
1: flash LED is strobing
+ - available_sync_leds - list of sub-LEDs available for flash strobe
+ synchronization (RO)
"space separated"?
- available_sync_leds - space separated list of sub-LEDs available for
flash strobe synchronization; each sub-LED is
described in the form of chunks:
[led_id: led_name]
So this will say something like "0 3 5"
Rather e.g.: [0: none] [1: max77693-led1] [2: max77693-led2]
+ - flash_sync_strobe - identifier of the sub-LED to synchronize the flash
+ strobe with; 0 stands for no synchronization (RW)
...and it means that I can put 0, 3 or 5 into this file?
Yes.
+ - flash_fault - list of flash faults that may have occurred:
"space separated"?
Right.
+ * led-over-voltage - flash controller voltage to the flash LED
+ has exceededthe limit specific to the flash controller
+ * flash-timeout-exceeded - the flash strobe was still on when
+ the timeout set by the user has expired; not all flash
+ controllers may set this in all such conditions
+ * controller-over-temperature - the flash controller has
+ overheated
+ * controller-short-circuit - the short circuit protection
+ of the flash controller has been triggered
+ * led-power-supply-over-current - current in the LED power
+ supply has exceeded the limit specific to the flash
+ controller
+ * indicator-led-fault - the flash controller has detected
+ a short or open circuit condition on the indicator LED
+ * led-under-voltage - flash controller voltage to the flash
+ LED has been below the minimum limit specific to
+ the flash
+ * controller-under-voltage - the input voltage of the flash
+ controller is below the limit under which strobing the
+ flash at full current will not be possible;
+ the condition persists until this flag is no longer set
+ * led-over-temperature - the temperature of the LED has exceeded
+ its allowed upper limit
+
+ Flash faults should be read in the strobe_set callback, right
+ after the instruction initiating the strobe. If a flash LED
Ok, so this is part sysfs documentation, part kernel class
documentation... it is a bit confusing.
As it documents the class itself it is convenient that all information
is available in one place. LED class documentation
Documentation/leds/leds-class.txt also contains information about
sysfs attributes semantics.
--
Best Regards,
Jacek Anaszewski
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