(Sorry your mail was lost due to mail outage) On 05/30/12 05:16, Ohad Ben-Cohen wrote: > > On Wed, May 30, 2012 at 11:36 AM, Stephen Boyd <sboyd@xxxxxxxxxxxxxx> wrote: > >> One complaint I've gotten is that the error messages are essentially >> useless now. I believe there are some ongoing discussions on lkml to fix >> this by traversing the device hierarchy to find the "real" device but >> the hard part is finding the real device. > You probably refer to the discussions around the input subsystem's pull request. > > I was thinking about that too when creating this patch, and it looks > like whatever Greg will come up with on that matter will benefit us > too. So taking that into account, it might make more sense to do stick > with the virtual device rather than use the real one here (we'll end > up having more information in the long run). Fair enough. Hopefully something comes out of that discussion since this will need it. >> I'm not clear on busses versus classes. > I think that busses is a whole lot more complex beast. Probably the > main indication we want one is when we need to match drivers to > devices. > > In this case, I was more wondering between using a class to a device type. > >> I recall seeing a thread where >> someone said classes were on the way out and shouldn't be used but I >> can't find it anymore. > I also remembered a similar discussion at a plumbers mini-conf about > 2-3 years ago too, so I looked at device_type as an alternative to > class. The former looks somewhat simpler, but I couldn't find any > major advantage for using one over the other, and both seem to be in > use by many subsystems. > >> Should we use classes for devices that will never >> have a matching driver? > It's not strictly required, but in case we want to provide these > devices some common behavior (and in our case we want them all to have > the same release handler, and very soon, the same PM handlers, too), > then a class (or a type) is helpful. > > It looks like moving from a class to a type is quite trivial, in case > classes do eventually go away (or an advantage of using the latter > shows up), but I'm not aware of any other viable alternative for us > other than class/type. > Ok. Will moving from a class to a device type disrupt the kernel ABI? First it will be under /sys/class/ and then under /sys/bus? Greg, can you shed some light on when to use a class versus a device type? -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
