On Tue, Nov 4, 2014 at 10:45 AM, Bastien Nocera <hadess@xxxxxxxxxx> wrote: > On Tue, 2014-11-04 at 10:37 +0200, Daniel Baluta wrote: >> On Tue, Nov 4, 2014 at 10:27 AM, Bastien Nocera <hadess@xxxxxxxxxx> wrote: >> > On Tue, 2014-11-04 at 10:18 +0200, Daniel Baluta wrote: >> >> On Tue, Nov 4, 2014 at 1:01 AM, Bastien Nocera <hadess@xxxxxxxxxx> wrote: >> >> > On Wed, 2014-10-29 at 19:30 +0100, Lars-Peter Clausen wrote: >> >> >> On 10/29/2014 06:47 PM, Bastien Nocera wrote: >> >> >> > On Wed, 2014-10-29 at 18:39 +0100, Lars-Peter Clausen wrote: >> >> >> >> On 10/29/2014 06:33 PM, Bastien Nocera wrote: >> >> >> >>> On Wed, 2014-10-29 at 18:21 +0100, Lars-Peter Clausen wrote: >> >> >> >>>> On 10/29/2014 03:30 PM, Bastien Nocera wrote: >> >> >> >>>>> Hey, >> >> >> >>>>> >> >> >> >>>>> I've posted this a couple of days ago: >> >> >> >>>>> http://www.hadess.net/2014/10/a-gnome-kernel-wishlist.html >> >> >> >>>>> along with a mail to LKML: >> >> >> >>>>> http://thread.gmane.org/gmane.linux.kernel/1810083 >> >> >> >>>>> >> >> >> >>>>> I've recently added to my list an item about IIO: >> >> >> >>>>> https://wiki.gnome.org/BastienNocera/KernelWishlist >> >> >> >>>>> >> >> >> >>>>> Are there any plans for a better API for the IIO subsystem? The API >> >> >> >>>>> might be good enough to drive from shell scripts, or helpers that only >> >> >> >>>>> need to work with one variant of a device, but my attempts at trying to >> >> >> >>>>> use the IIO subsystem to provide an accelerometer to do automatic >> >> >> >>>>> display rotation[1] showed that the API is really cumbersome. >> >> >> >>>>> >> >> >> >>>>> The code I wrote spends most of its time creating sysfs paths, reading >> >> >> >>>>> values in different formats, and mangling filenames[2]. >> >> >> >>>>> >> >> >> >>>>> Is an ioctl-based API planned? Something where I could get/set >> >> >> >>>>> structures to gather metadata about the device, and set it up easily, so >> >> >> >>>>> reading data from it is easier? >> >> >> >>>> >> >> >> >>>> No, unfortunately not and I'm not sure if such a ABI would be accepted if >> >> >> >>>> proposed. >> >> >> >>> >> >> >> >>> Why not? >> >> >> >> >> >> >> >> Because it means there will be ambiguity in the API on how to do things. >> >> >> >> Which is typically not a desired property. >> >> >> >> >> >> >> >>> >> >> >> >>>> But checkout libiio[1][2], it hides the details of the sysfs file manipulation. >> >> >> >>> >> >> >> >>> I'm not sure that's any better unfortunately. I've certainly tried to do >> >> >> >>> that already in my code, but that doesn't change that the user-space API >> >> >> >>> is barely usable. >> >> >> >> >> >> >> >> It's not completely unusable ;) >> >> >> > >> >> >> > In the end, you prefer the "self-documenting" of using sysfs files, >> >> >> > rather than an API which you can document in a header file? >> >> >> >> >> >> If it was for me we'd be using a state-full IOCTL ABI rather than a >> >> >> stateless sysfs ABI. I'm definitely not happy with the current interface, >> >> >> but it's the interface we have. But the problem with userspace ABI (in >> >> >> comparison to in-kernel API) is that we can just change things at random, >> >> >> but we have to stick with the existing interface. >> >> >> >> >> >> The sysfs ABI is not meant to be self documenting and it is not >> >> >> undocumented. The documentation for the different attributes can be found in >> >> >> Documentation/ABI/testing/sysfs-bus-iio[1]. >> >> > >> >> > That's useful if a bit terse. Thanks though. >> >> > >> >> >> > I don't understand that. My questions on this very mailing-list, and >> >> >> > comments that were made to users of my code[1] clearly show that the >> >> >> > existing API is anything but "not ambiguous". >> >> >> >> >> >> That bug report sounds like bugs in the driver. >> >> > >> >> > Not really. Some drivers need the "in_accel_hysteresis" set, some don't >> >> > have that sysfs file, for example. >> >> > >> >> >> > I've used the Bluetooth, input, rfkill, and inotify APIs as provided >> >> >> > directly by the Linux kernel (not through a layer) and they're of better >> >> >> > quality than the IIO one. >> >> >> > >> >> >> > I just don't see how one could support a class of IIO sensors with the >> >> >> > existing API. >> >> >> >> >> >> I can understand your frustration. A API that is not usable in a generic way >> >> >> is not really useful. So we should try to fix that, but we are bound by the >> >> >> framework itself and can't just throw everything away. >> >> >> >> >> >> So lets start by trying to identify what is missing. Which information do >> >> >> you think could be provided by using a IOCTL interface which you need or >> >> >> want which is not provided by the current sysfs interface or can not be >> >> >> provided by the current sysfs interface. >> >> > >> >> > (pseudo code ahead) >> >> > >> >> > First, being able to cut down on the string manipulation would be great. >> >> > So instead of doing: >> >> > accel_x_path = build_filename (sysfs_path, "in_accel_x_raw"); >> >> > accel_y_path = build_filename (sysfs_path, "in_accel_y_raw"); >> >> > accel_z_path = build_filename (sysfs_path, "in_accel_z_raw"); >> >> > if (exists(accel_x_path) && exists(accel_y_path) && exists(accel_z_path)) { >> >> > // We have an accelerometer >> >> > do_something(); >> >> > } >> >> > free(..x); >> >> > free(..y); >> >> > free(..z); >> >> > free(sysfs_path); >> >> > >> >> > I could query for the device's capabilities: >> >> > fd = open ("/dev/iio0"); >> >> > ioctl(fd, IIO_GET_CAPS, &caps); >> >> > if (caps.channels & (IIO_CAP_ACCEL_X | IIO_CAP_ACCEL_Y | IIO_CAP_ACCEL_Z)) { >> >> > // We have an accelerometer >> >> > do_something(); >> >> > } >> >> > >> >> > Note that, from the data given, I don't know how to make out whether >> >> > something is an accelerometer, or a quartenion sensor, or which one we >> >> > should prefer on specific machines. >> >> > >> >> > This would also be stateful, so that 1) enabling the various channels, >> >> > 2) changing the hysteresis would be reset when the fd is closed. That >> >> > would cut down on the power consumption when unused, or when the service >> >> > that uses that data crashes. >> >> > >> >> > Finally, there's some documentation, and it's not quite finished, or >> >> > there's something fishy on this device: >> >> > $ ls /sys//devices/platform/80860F41:04/i2c-12/i2c-SMO8500:00/iio:device0/events >> >> > in_accel_x_thresh_thresh_en in_accel_x_thresh_thresh_value >> >> > in_accel_y_thresh_thresh_period in_accel_z_thresh_thresh_en >> >> > in_accel_z_thresh_thresh_value >> >> > in_accel_x_thresh_thresh_period in_accel_y_thresh_thresh_en >> >> > in_accel_y_thresh_thresh_value in_accel_z_thresh_thresh_period >> >> >> >> Could you paste here the initialization part of iio_chan_spec + iio_event_spec? >> > >> > How would I do that? >> >> Just look into the code and search for iio_chan_spec and >> iio_event_spec declaration. > > Oh, the code. Well, you've already sent a patch for it, so you should > know ;) > > I've sent the patch adding support for the accelerometer in my device > yesterday: > http://thread.gmane.org/gmane.linux.kernel.iio/14487 > > I'll test your patch in a little while once I've had the chance to play > with the Bluetooth support code. I forgot that SMO8500 is KXCJ9. Should work with https://lkml.org/lkml/2014/10/10/249 :). Daniel. -- 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
