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    SubjectRe: [PATCH/RFC v4 15/21] media: Add registration helpers for V4L2 flash
    Hi Sakari,

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

    [...]
    >>>>
    >>>> 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



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