On Fri, Sep 05, 2014 at 11:04:18PM -0600, Azael Avalos wrote: > Hi there, > > 2014-09-05 20:42 GMT-06:00 Darren Hart <dvhart@xxxxxxxxxxxxx>: > > On Fri, Sep 05, 2014 at 11:14:05AM -0600, Azael Avalos wrote: > >> The accelerometer sensor is very sensitive, and having userspace > >> poll the sysfs position entry is not very battery friendly. > >> > >> This patch removes the sysfs entry and instead, it creates an > >> input polled device (joystick) for the built-in accelerometer. > > > > Hrm, while sysfs details can change across kernel versions, usually due to > > driver core changes, we try to keep them as consistent as possible so as not to > > break userspace. > > > > That said, if we are going to try and come up with a better model for > > representing an accelerometer, wouldn't treating it as an IIO device be the more > > logical approach? > > Yes of course, but the actual accelerometer device (sensor?) is not > really exposed, > only certain "functions" it provides, and they are divided across two > different ACPI devices, > TOS620A exposes the protection, and the TOS1900 (and et. al.) only > exposes the axes. As I understand it, IIO defines an interface to a device, a standard sysfs set of properties. I should think we could provide the appropriate callbacks even for a partially implemented (or a pair of) accelerometer. Jonathan, what are your thoughts here. Is such a "device" (ACPI accessors to axis and threshold) a candidate for IIO, or is this input polled device more appropriate? > > I see your point in breaking userspace, but given the fact that it was > recently introduced, > I didn't thought it was already "adopted", that's why I decided to > remove the sysfs entry. Looks like since 3.15 if I read the log correctly. That is fairly recent and this is not one of the "defined interfaces" in the sysfs documentation. Greg, can you weigh in here - does this change count as "breaking userspace", or is this more inline with the scheduler knobs in /proc/sched_debug which can change from version to version. > > Then we might as well keep the sysfs entry and have the input polled > device as well. Let's see what Greg has to say. If he isn't bothered by the change, I won't push the issue. -- Darren Hart Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
