Hi!
> >>+ - flash_fault - list of flash faults that may have occurred:
> >>+ * 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 are cleared, if possible, by reading the attribute.
> >
> >That's bad. Now you can no longer present flash_fault file as readable
> >to non-root users, and grep -ri foo /sys will interfere with your
> >camera application.
> >
> >Bad interface, just fix it.
>
> In my opinion it isn't crucial for the user to be aware of the
> fact that some non-persistent fault happened right after strobing the
> flash (e.g. over temperature).
>
> I cannot see anything harmful in the situation when someone does grep
> on /sys and clears non-persistent fault on a flash LED device.
So why export the faults at all?
I mean... another user can just read the file in loop, and the camera
application will not get any useful information.
> Also, not all devices may be able to report the faults that happened
> earlier but are not valid at the time of I2C readout. In that case the
> user will never now that the fault has ever occurred, unless they read
> the flash_fault attribute at the proper moment.
>
> In this case we cannot enforce consistent policy for all devices.
Too bad. But lets do a good job at least for devices where we can do a
good job, ok?
> Please describe the use case when clearing the fault on read can be
> harmful, if you have any.
while true; grep -ri foo /sys; done
And no, your application trying to read the faults will very probably
read nothing.
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures)
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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