Hi Sakari,

On 08/20/2014 04:41 PM, Sakari Ailus wrote:

Hi Jacek,

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LED Class Flash driver gains V4L2 Flash API when
CONFIG_V4L2_FLASH_LED_CLASS is defined. This is accomplished in
the probe function by either calling v4l2_flash_init function
or the macro of this name, when the CONFIG_V4L2_FLASH_LED_CLASS
macro isn't defined.

If the v4l2-flash.c was to call the LED API directly, then the
led-class-flash module symbols would have to be available at
v4l2-flash.o linking time.

Is this an issue? EXPORT_SYMBOL_GPL() for the relevant symbols should be
enough.

It isn't enough. If I call e.g. led_set_flash_brightness
directly from v4l2-flash.c and configure led-class-flash to be built as
a module then I am getting "undefined reference to
led_set_flash_brightness" error during linking phase.

You should not. You also should change the check as (unless you've changed
it already):

#if IS_ENABLED(CONFIG_V4L2_FLASH_LED_CLASS)

This will evaluate to non-zero if the macro arguent or the argument
postfixed with "_MODULE" is defined.

I've missed this macro. Indeed, it is possible to avoid the need
for ops with it. I will fix it in the next version of the patch set.
Thanks for the hint.

Best Regards,
Jacek Anaszewski