Re: [PATCH/RFC v9 02/19] Documentation: leds: Add description of LED Flash class extension
Hi Sakari, On 12/09/2014 01:38 PM, Sakari Ailus wrote: [...] 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. I meant that how does the user figure out which LEDs may be strobed synchronously, together. Say, if you have two of these chips and four LEDs, then how does it work? :-) User can figure it out by checking the existence of the flash_sync_strobe attribute. Sub-leds can by synchronized only when are driven by common chip. It is assumed that sub-leds of one chip will have common segment in their name, defined in DT 'label' property. Maybe we should enforce it by adding another property to the leds/common.txt DT binding, e.g. 'device-prefix'? Best Regards, Jacek Anaszewski -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH/RFC v9 02/19] Documentation: leds: Add description of LED Flash class extension
Hi Jacek, On Thu, Dec 04, 2014 at 10:42:55AM +0100, Jacek Anaszewski wrote: > 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 > >>Acked-by: Kyungmin Park > >>Cc: Bryan Wu > >>Cc: Richard Purdie > >>--- > >> 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 000..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. Agreed. > >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. I meant that how does the user figure out which LEDs may be strobed synchronously, together. Say, if you have two of these chips and four LEDs, then how does it work? :-) -- Kind regards, Sakari Ailus e-mail: sakari.ai...@iki.fi XMPP: sai...@retiisi.org.uk -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH/RFC v9 02/19] Documentation: leds: Add description of LED Flash class extension
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 Acked-by: Kyungmin Park Cc: Bryan Wu Cc: Richard Purdie --- 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 000..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 -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH/RFC v9 02/19] Documentation: leds: Add description of LED Flash class extension
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 > Acked-by: Kyungmin Park > Cc: Bryan Wu > Cc: Richard Purdie > --- > 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 000..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. How does the user btw. figure out which flash LEDs may be strobed synchronously using the LED flash interface? > + - 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 > + > + Flash faults are cleared by reading the attribute. -- Kind regards, Sakari Ailus e-mail: sakari.ai...@iki.fi XMPP: sai...@retiisi.org.uk -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
