Hey, On Mon, 2016-09-12 at 17:25 +0200, Hans de Goede wrote: > Hi Bastien, > > So as I guess you sorta know in my spare time I work on Linux > (mainline) support for Allwinner SoC based ARM devices, including > a whole lot of cheap Chinese tablets. > > Recently I've begun looking into supporting the accelerometers > on these devices and I'm making good progress on getting the > kernel bits working using iio drivers (including a few new > ones I've written recently). > > Yesterday I realized there is a bit of a catch though, all > these iio drivers report results assuming that the accelerometer > is mounted on the top side of the PCB and with its X/Y > coordination properly taken info account. > > Unfortunately neither is necessarily true. Almost all > tablet PCBS are mounted upside down (with an empty PCB > backside against the lcd-panel. Meaning that the Z axis > reads -1G when the tablet is lying on its back instead > of the expected +1G and some need X/Y axis swapping and/or > inversion too. > > So there are 3 problems here: > > 1) Where do we store the orientation of the chip > <snip> > 2) Where do we correct the readings for the orientation <snip> > 3) Currently implementing orientation support in an iio driver > requires copy and pasting quite a bit of boiler plate, so > a question to the linux-iio list, has anyone though of an > easier way to do this. I really just want to be able to > pass say a single flag to iio_device_register and then > have the iio-core automatically call of_iio_read_mount_matrix() > and add mount_matrix ext_info. All good ideas, but we need a way to do this for devices without DT (meaning all of the x86 tablets). Perhaps iio-sensor-proxy could read from udev instead, and udev either pull from DT when available, or apply from its own rules? Cheers -- 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
