Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH 2/6] ASoC: codecs: AK4641 depends on GPIOLIB | Date | Mon, 03 Oct 2011 12:59:58 +0200 |
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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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