On September 9, 2014 1:04:30 AM GMT+01:00, Darren Hart <dvhart@xxxxxxxxxxxxx> wrote: >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? Absolutely fine in IIO. Sorry I took so long to reply. Read the title and expected more detailed issue so queued it up for when I had more time. Oops. Only slight gotcha is that there is some debate over the iio timer trigger configuration interface which would be equivalent of a polled input device. Hence it hasn't merged yet. Comes down to how these are instantiated. Lars-Peter Clausen is planning a configfs proposal rather than how we do the user space trigger creation currently. A user space trigger would work but then you loose lack of hitting sysfs files. > >> >> 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. -- Sent from my Android phone with K-9 Mail. Please excuse my brevity. -- 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
