On Monday, June 13, 2011 00:06:19 Mauro Carvalho Chehab wrote: > Em 12-06-2011 15:09, Hans Verkuil escreveu: > > On Sunday, June 12, 2011 19:27:21 Mauro Carvalho Chehab wrote: > >> Em 12-06-2011 13:07, Hans Verkuil escreveu: > >>> On Sunday, June 12, 2011 16:37:55 Mauro Carvalho Chehab wrote: > >>>> Em 12-06-2011 07:59, Hans Verkuil escreveu: > >>>>> From: Hans Verkuil <hans.verkuil@xxxxxxxxx> > >>>>> > >>>>> The check_mode function checks whether a mode is supported. So calling it > >>>>> supported_mode is more appropriate. In addition it returned either 0 or > >>>>> -EINVAL which suggests that the -EINVAL error should be passed on. However, > >>>>> that's not the case so change the return type to bool. > >>>> > >>>> I prefer to keep returning -EINVAL. This is the proper thing to do, and > >>>> to return the result to the caller. A fixme should be added though, so, > >>>> after someone add a subdev call that would properly handle the -EINVAL > >>>> code for multiple tuners, the functions should return the error code > >>>> instead of 0. > >>> > >>> No, you can't return -EINVAL here. It is the responsibility of the bridge > >>> driver to determine whether there is e.g. a radio tuner. So if one of these > >>> tuner subdevs is called with mode radio while it is a tv tuner, then that > >>> is not an error, but instead it is a request that can safely be ignored > >>> as not relevant for that tuner. It is up to the bridge driver to ensure > >>> that a tuner is loaded that is actually valid for the radio mode. > >>> > >>> Subdev ops should only return errors when there is a real problem (e.g. i2c > >>> errors) and should just return 0 if a request is not for them. > >>> > >>> That's why I posted these first two patches: these functions suggest that you > >>> can return an error if the mode doesn't match when you really cannot. > >>> > >>> If I call v4l2_device_call_until_err() for e.g. s_frequency, then the error > >>> that is returned should match a real error (e.g. an i2c error), not that one > >>> of the tv tuners refused the radio mode. I know there is a radio tuner somewhere, > >>> otherwise there wouldn't be a /dev/radio node. > >>> > >>> I firmly believe that the RFCv4 series is correct and just needs an additional > >>> patch adding some documentation. > >>> > >>> That said, it would make sense to move the first three patches to the end > >>> instead if you prefer. Since these are cleanups, not bug fixes like the others. > >> > >> > >> The errors at tuner should be propagated. If there's just one tuner, the error > >> code should just be returned by the ioctl. But, if there are two tuners, if the bridge > >> driver calls G_TUNER (or any other tuner subdev call) and both tuners return -EINVAL, > >> then it needs to return -EINVAL to userspace. If just one returns -EINVAL, and the > >> other tuner returns 0, then it should return 0. So, it is about the opposite behaviour > >> implemented at v4l2_device_call_until_err(). > > > > Sorry, but no, that's not true. You are trying to use the error codes from tuner > > subdevs to determine whether none of the tuner subdevs support a certain tuner mode. > > Not only that. There are some cases where the tuner driver may not bind for some reason. > So, even if the bridge driver does support a certain mode, a call to G_TUNER may fail > (for example, if tea5767 probe failed). Only with a proper return code, the bridge driver > can detect if the driver found some issue. Surely, that's an error reported by tuner_probe, isn't it? That's supposed to ensure that the tuner driver was loaded and initialized correctly. I'm not sure if it does, but that's definitely where any errors of that kind should be reported. Looking at it some more, it seems to me that s_type_addr should also return an error if there are problems. Ditto for tuner_s_config. An alternative solution is to keep a 'initialized' boolean that is set to true once the tuner is fully configured. If g_tuner et al are called when the tuner is not fully configured, then you can return -ENODEV or -EIO or something like that. But that's a separate status check and has nothing to do with mode checking. > > E.g., you want to change something for a radio tuner and there are no radio tuner > > subdevs. But that's the job of the bridge driver to check. That has the overview, > > the lowly subdevs do not. The subdevs just filter the ops and check the mode to see > > if they should handle it and ignore it otherwise. > > > > Only if they have to handle it will they return a possible error. The big problem > > with trying to use subdev errors codes for this is that you don't see the difference > > between a real error of a subdev (e.g. -EIO when an i2c access fails) and a subdev > > that returns -EINVAL just because it didn't understand the tuner mode. > > > > So the bridge may return -EINVAL to the application instead of the real error, which > > is -EIO. > > An -EIO would also be discarded, as errors at v4l2_device_call_all() calls don't return > anything. So, currently, the bridge has to assume that no errors happened and return 0. Obviously, v4l2_device_call_all calls should be replaced with v4l2_device_call_until_err. I've no problem with that. > > > That's the whole principle behind the sub-device model: sub-devices do not know > > about 'the world outside'. So if you pass RADIO mode to S_FREQUENCY and there is no > > radio tuner, then the bridge driver is the one that should detect that and return > > -EINVAL. > > > > Actually, as mentioned before, it can also be done in video_ioctl2.c by checking > > the tuner mode against the device node it's called on. But that requires tightening > > of the V4L2 spec first. > > Yes, video_ioctl2 (or, currently, the bridge driver) shouldn't allow an invalid operation. > But if the call returns an error, this error should be propagated. > > Also, as I've explained before, even adding the invalid mode check inside video_ioctl, > you may still have errors if the registered tuners don't support the mode, because one > of the tuners didn't registered properly. And that's something that tuner_probe/s_type_addr/s_config should have detected. Or, should that be impossible (I would have to spend more time to analyze that) we might have to add a 'validate_tuner' op that can be called to verify all tuners are configured correctly. Regards, Hans -- 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
