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    SubjectRe: [PATCH 2/6] ASoC: codecs: AK4641 depends on GPIOLIB
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    On Sunday 02 October 2011 22:27:11 Mark Brown wrote:
    > > Is there any other symbol that I can test then?
    >
    > You shouldn't be testing anything - the client side GPIO API (which is
    > what this driver is using) is supposed to stub itself out when not in
    > use so drivers should just be able to use it without worrying about
    > dependencies. You didn't report the problem but I'd expect that
    > whatever you saw will be an issue in whatever platform you were trying
    > to build for (I'm guessing it hasn't provided gpio_request_one()),
    > though it could be a problem in the gpiolib stubs if that's being used.

    I don't remember where I first saw it. If the problem comes back,
    I'll do a full bug report. I've verified now that it works on
    various platforms with and without GPIOLIB.

    I didn't know how the GPIO bits fit together, so I ended up doing
    something that made the problem go away, whatever it was. This
    is of course a problem with the randconfig fixing: One really needs
    to understand every possible corner of the kernel to get it right,
    and if you don't you end up with a patch that avoids the symptom
    without fixing the underlying bug and then you make it harder to
    find.

    I really appreciate you doing the thorough review of the patches
    to make sure we find the actual bugs, which is one of the main
    things I want to achieve here anyway.

    > > I noticed that a lot of places use 'depends on GPIOLIB' or
    > > '#ifdef CONFIG_GPIOLIB', are those usually wrong, too?
    >
    > Checks for gpiolib in drivers providing GPIOs are sensible, if a
    > platform hasn't used gpiolib then it's generally not even got an
    > interface for drivers to provide GPIOs.
    >
    > On the user side these are usually due to people making the sort of
    > changes you're making here due to a random build coverage issue - it
    > seems unfortunately common for people to just shove a dependency in
    > Kconfig when they run into a build coverage issue without looking at
    > what's going on. For a lot of the stuff you see on PCs it's going to
    > make sense but for some of the "service" APIs like GPIOs that are more
    > commonly used only in embedded contexts the use of the API is usually
    > completely optional (eg, in this case the driver is controlling power
    > and reset lines which could easily just be strapped in the hardware with
    > no soft control and are supplied as optional platform data) so for many
    > systems the driver is going to work completely happily without doing
    > anything with GPIOs.
    >
    > Adding dependencies to all the users needlessly restricts which systems
    > can use the drivers. Adding ifdefs to the drivers is repetitive and
    > isn't great for legiblity, having the header stub itself out is simpler
    > and easier to use on the driver side.

    Ok, makes sense. Thanks for the background information!

    Arnd


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