Hi Bryan,
Thanks for a review.
On 11/13/2014 07:58 PM, Bryan Wu wrote:
On Wed, Nov 12, 2014 at 8:09 AM, Jacek Anaszewski
<j.anaszewski@xxxxxxxxxxx> 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@xxxxxxxxxxx>
Acked-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
Cc: Bryan Wu <cooloney@xxxxxxxxx>
Cc: Richard Purdie <rpurdie@xxxxxxxxx>
---
Documentation/leds/leds-class-flash.txt | 39 +++++++++++++++++++++++++++++++
1 file changed, 39 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..0164329
--- /dev/null
+++ b/Documentation/leds/leds-class-flash.txt
@@ -0,0 +1,39 @@
+
+Flash LED handling under Linux
+==============================
+
+Some LED devices support two modes - torch and flash. In order to enable
I think I asked this question before, Torch, Flash and Indicator. As
you answered torch is implemented by sync led brightness set operation
in our LEDS_CLASS and Flash is implemented in this LEDS_CLASS_FLASH.
I suggest put this information in document or code comments. Then
people know how to use torch and flash.
Good point.
For indicator I still don't know why we need this since indicator is
like blinking and it should be support by LEDS_CLASS right?
Indicator led is strictly related to flash devices. It is also called a
"privacy led" because of its purpose - protecting a privacy of a person
being recorded by providing a light signal signifying that a camera is
on. It is a low current led, but some devices use the same led as
for torch and flash and only apply reduced current in the indicator
mode.
In the V4L2 subsystem I see only one driver supporting indicator
leds: /drivers/media/i2c/as3645a.c. It looks like indicator intensity
can be set only when flash mode is V4L2_FLASH_LED_MODE_NONE, i.e. torch
and flash leds cannot be active simultaneously with indicator led.
It is reasonable, as active torch led is a sufficient signalization
of recording.
In the LED subsystem I also see indicators in some drivers,
e.g. leds-lm355x.c, but they are registered as a separate LED class
devices. Moreover the driver adds also a "pattern" sysfs attribute
for choosing indicator blinking pattern so that is something to be
added to the LED Flash class.
I think that similar improvement to the V4L2 Flash API should be made.
Sakari, what is your opinion?
Flash is for some camera capture, right?
+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)
+ - indicator_brightness - privacy LED brightness in microamperes (RW)
+ - max_indicator_brightness - maximum privacy LED brightness in
+ microamperes (RO)
What's the privacy mean here?
Indeed, consistent naming should be applied, so I will modify it to:
"maximum indicator LED brightness in microaperes (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_fault - bitmask of flash faults that may have occurred,
+ possible flags are:
+ * 0x01 - flash controller voltage to the flash LED has exceeded
+ the limit specific to the flash controller
+ * 0x02 - 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
+ * 0x04 - the flash controller has overheated
+ * 0x08 - the short circuit protection of the flash controller
+ has been triggered
+ * 0x10 - current in the LED power supply has exceeded the limit
+ specific to the flash controller
+ * 0x40 - flash controller voltage to the flash LED has been
+ below the minimum limit specific to the flash
+ * 0x80 - 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
+ * 0x100 - the temperature of the LED has exceeded its allowed
+ upper limit
Are these error code the same for all the LED controller? Or just for
some specific chip?
They are generic error codes, and map directly to V4L2 Flash errors.
Error descriptions were copied from the V4L2 Flash documentation.
Best Regards,
Jacek Anaszewski
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