Em Fri, 28 Jun 2013 13:18:44 +0200 Hans Verkuil <hverkuil@xxxxxxxxx> escreveu: > On Fri June 28 2013 13:00:43 Mauro Carvalho Chehab wrote: > > Em Fri, 28 Jun 2013 10:24:15 +0200 > > Hans Verkuil <hverkuil@xxxxxxxxx> escreveu: > > > > > This fixes a dependency problem as found by Randy Dunlap: > > > > > > https://lkml.org/lkml/2013/6/27/501 > > > > > > Mauro, is there any reason for any V4L2 driver to depend on VIDEO_DEV instead of > > > just VIDEO_V4L2? > > > > > > Some drivers depend on VIDEO_DEV, some on VIDEO_V4L2, some on both. It's all > > > pretty chaotic. > > > > It should be noticed that, despite its name, this config is actually a > > joint dependency of VIDEO_DEV and I2C that will compile drivers as module > > if either I2C or VIDEO_DEV is a module: > > > > config VIDEO_V4L2 > > tristate > > depends on (I2C || I2C=n) && VIDEO_DEV > > default (I2C || I2C=n) && VIDEO_DEV > > > > So, a V4L2 device that doesn't have any I2C device doesn't need to depend > > on VIDEO_V4L2. That includes, for example, reversed-engineered webcam > > drivers where the sensor code is inside the driver and a few capture-only > > device drivers. > > Yes, it does have to depend on it. That's exactly why usbtv is failing: like > any other v4l2 driver usbtv needs the videodev.ko module. That is dependent > on VIDEO_V4L2. What is happening here is that the dependency of usbtv on > VIDEO_DEV allows it to be built as part of the kernel, but VIDEO_V4L2 is built > as a module due to its I2C dependency with the result that usbtv can't link to > the videodev functions. > > The way things are today I do not believe any v4l2 driver should depend on > VIDEO_DEV, instead they should all depend on VIDEO_V4L2. That would make a > lot more sense. Hmm... $ git grep -l i2c drivers/media/v4l2-core/ drivers/media/v4l2-core/tuner-core.c (not part of videodev.ko module) drivers/media/v4l2-core/v4l2-async.c drivers/media/v4l2-core/v4l2-common.c drivers/media/v4l2-core/v4l2-ctrls.c (actually, there's just a comment there) drivers/media/v4l2-core/v4l2-device.c $ git grep CONFIG_I2C drivers/media/v4l2-core/ drivers/media/v4l2-core/v4l2-common.c:#if IS_ENABLED(CONFIG_I2C) drivers/media/v4l2-core/v4l2-common.c:#endif /* defined(CONFIG_I2C) */ drivers/media/v4l2-core/v4l2-device.c:#if IS_ENABLED(CONFIG_I2C) yes, there are some parts of videodev that are dependent on I2C. That's basically why all V4L2 drivers should depend on VIDEO_V4L2. That's said, before the addition of v4l2-async, it was safe to compile the core without I2C, as the parts of the code that are I2C specific are protected by a: #if defined(CONFIG_I2C) With its addition, I suspect that we'll still have Kbuild issues, if I2C is disabled and a driver that doesn't depends on I2C is compiled. So, 2 patches seem to be needed: 1) a patch that replaces all driver dependencies from CONFIG_DEV to CONFIG_V4L2; 2) a patch that fixes the issues with v4l2-async. With regards to the last one, I can see 3 ways to fix it: 1) don't add v4l2-async at videodev.ko if I2C is not selected; 2) protect the I2C specific parts of v4l2-async with #if defined(CONFIG_I2C) 3) put v4l2-async on a separate module. (or some combination of the above) As only very few drivers use v4l2-async, as this is more focused to fix troubles with OT, I think that the better would be to do (3) and to add an specific Kconfig entry for it. Regards, Mauro. -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
