|From:||Jonathan Cameron <firstname.lastname@example.org>|
|Subject:||[RFC] Staging:IIO: New ABI|
|Date:||Wed, 20 Jan 2010 15:13:40 +0000|
|Cc:||Manuel Stahl <email@example.com>, "Hennerich, Michael" <Michael.Hennerich@analog.com>, "Frysinger, Michael" <Michael.Frysinger@analog.com>, "Getz, Robin" <Robin.Getz@analog.com>, Greg KH <firstname.lastname@example.org>, Jean Delvare <email@example.com>, "Trisal, Kalhan" <firstname.lastname@example.org>, "Zhang, Xing Z" <email@example.com>, Ira Snyder <firstname.lastname@example.org>|
Dear All, An extensive conversation with Manuel Stahl that grew out of his work on an ADIS16400 driver and the userspace IIO tools at iioutils.sourceforge.net showed that there were a number of significant short comings in the current IIO ABI. Some of these were simply things that have never been pinned down, others are down to silly issues with how the code has developed. Hence Manuel and I have drawn up a new ABI specification. With hindsight we should probably have held the entire conversation publicly but this document will hopefully act as summary. Please forgive the flagrant abuse of syntax in large parts of this file. This will all be cleaned up before a formal submission. At this stage what we are after is comments on the actual IIO sysfs ABI. There are doubtlessly unclear sections and elements we have forgotten completely so if you know of something that is missing (along with a concrete example of where it is needed, please do point it out!) To avoid an insanely long ABI spec, I've suppressed fields that are not of interest to this discussion and not specified some items that are similar in purpose to those given for volt channels. All comments welcome. One area of extreme complexity currently is that of event handling and specifically how come up with a consistent generalizable specification when there are so many different options. Comments / suggestions on this are particularly welcome! As ever, if people could forward / cc anyone how they think may be interested that would be great. The current cc list is based on a fairly rapid dash through previous threads. What: /sys/class/iio/device[n] Description: Hardware chip or device accessed by on communication port. Corresponds to a grouping of sensor channels. What: /sys/class/iio/trigger[n] Description: An event driven driver of data capture to an in kernel buffer. May be provided a device driver that also has an IIO device based on hardware generated events (e.g. data ready) or provided by other hardware (e.g. periodic timer or gpio) Contains trigger type specific elements. These do not generalize well. What: /sys/class/iio/ring_buffer[m] Description: Link to /sys/class/iio/device[n]/ring_buffer[m]. Ring buffer numbering may not match that of device as some devices do not have ring buffers. What: /sys/class/iio/device[n]/name Description: Description of the physical chip / device. Typically a part number. What: /sys/class/iio/device[n]/volt_[name][m]_raw Description: Raw (unscaled no bias removal etc) voltage measurement from channel m. name is used in special cases where this does not correspond to externally available input (e.g. supply voltage monitoring). What: /sys/class/iio/device[n]/volt_[name][m]_offset Description: If known for a device, offset to be added to volt[m]_raw prior to scaling by volt[m]_scale in order to obtain voltage in Volts. Not present if the offset is always 0 or unknown. If m is not present, then voltage offset applies to all volt channels. May be writable if a variable offset is controlled by the device. Note that this is different to calibbias which is for devices that apply offsets to compensate for variation between different instances of the part. What: /sys/class/iio/device[n]/volt_[name][m]_offset_available Description: If a small number of discrete offset values are available, this will be a space separated list. If these are independant (but options the same) for individual offsets then m should not be present. What: /sys/class/iio/device[n]/volt_[name][m]_offset_[min|max] Description: If a more or less continuous range of voltage offsets are supported then this specifies the minimum / maximum. If shared by all volt channels then m is not present. What: /sys/class/iio/device[n]/volt_[name][m]_calibbias Description: Hardware applied calibration offset. (assumed to fix production inaccuracies) What /sys/class/iio/device[n]/volt_[name][m]_calibscale Description: Hardware applied calibration scale factor. (assumed to fix production inaccuracies) What: /sys/class/iio/device[n]/volt_[name][m]_scale Description: If known for a device, scale to be applied to volt[m]_raw post addition of volt[m]_offset in order to obtain the measured voltage in volts. If shared across all voltage channels the m is not present. What: /sys/class/iio/device[n]/accel_[x|y|z][m]_raw Description: Acceleration in direction x, y or z (may be arbitrarily assigned but should match other such assignments on device) channel m (not present if only one accelerometer channel at this orientation). Has all of the equivalent parameters as per volt[m]. Units after application of scale and offset are m/s^2. What: /sys/class/iio/device[n]/gyro_[x|y|z][m]_raw Description: Angular velocity about axis x,y or z (may be arbitrarily assigned) channel m (not present if only one gyroscope at this orientation). Data converted by application of offset then scale to radians per second. Has all the equivalent parameters as per volt[m]. What: /sys/class/iio/device[n]/mag_[x|y|z][m]_raw Description: Magnetic field along axis x, y or z (may be arbitrarily assigned) channel m (not present if only one magnetometer at this orientation). Data converted by application of offset then scale to Gauss Has all the equivalent modifiers as per volt[m]. What: /sys/class/iio/device[n]/pressure[m]_raw Description: Barometric pressure //Lots more to add along a similar vain. What: /sys/class/iio/device[n]/event_line[m] Description: Configuration of which hardware generated events are passed up to userspace. Some of these are a bit complex to generalize so this section is a work in progress. What: /sys/class/iio/device[n]/event_line[m]/dev Description: major:minor character device numbers. Again taking accel_x0 as example and serious liberties with ABI spec. What: /sys/.../event_line[m]/accel_x0_thresh[_high|_low] Description: Event generated when accel_x0 passes a threshold in correction direction (or stays beyond one). If direction isn't specified, either triggers it. Note driver will assume last p events requested are enabled where p is however many it supports. So if you want to be sure you have set what you think you have, check the contents of these. Drivers may have to buffer any parameters so that they are consistent when a given event type is enabled a future point (and not those for whatever alarm was previously enabled). What: /sys/.../event_line[m]/accel_x0_roc[_high|_low] Description: Same as above but based on the first differential of the value. What: /sys/.../event_line[m]/accel_x0[_thresh|_roc][_high|_low]_period Description: A period of time (microsecs) for which the condition must be broken before an interrupt is triggered. Applies to all alarms if type is not specified. What: /sys/.../event_line[m]/accel_x0[_thresh|_roc][_high|_low]_value Description: The actual value of the threshold either in raw device units obtained by reverse application of scale and offfset to the acceleration in m/s^2. What: /sys/.../event_line[m]/free_fall Description: Common hardware event in accelerometers. Takes no parameters. There are many other weird and wonderful event types that we'll deal with as and when. Taking accel_x0 for example of next section. What: /sys/class/iio/device[n]/scan_elements/[m]_accel_x0_en Description: Scan element control for triggered data capture. m implies the ordering within the buffer. Next the type is specified with modifier and channel number as per the sysfs single channel access above. What: /sys/class/iio/device[n]/scan_elements/accel[_x0]_precision Description: Scan element precision within the ring buffer. Note that the data alignment must restrictions must be read from in ring_buffer to work out full data alignment for data read via ring_access chrdev. _x0 dropped if shared across all acceleration channels. What: /sys/class/iio/device[n]/scan_elements/accel[_x0]_shift Description: A bit shift (to right) that must be applied prior to extracting the bits specified by accel[_x0]_precision. What: /sys/class/iio/device[n]/ring_buffer[m] Description: Ring buffer specific parameters separate. Some are influenced by scan_elements. What: /sys/.../ring_buffer[m]/ring_event[o]/dev Description: Ring buffer m event character device o major:minor numbers. What: /sys/.../ring_buffer[m]/ring_access[o]/dev Description: Ring buffer m access character device o major:minor numbers. What: /sys/.../ring_buffer[m]/trigger Description: The name of the trigger source being used, as per string given in /sys/class/iio/trigger[n]/name. What: /sys/.../ring_buffer[m]/length Description: Number of scans contained by the buffer. What: /sys/.../ring_buffer[m]/bps Description: Bytes per scan. Due to alignment fun, the scan may be larger than implied directly by the scan_element parameters. What: /sys/.../ring_buffer[m]/enable Description: Actually start the ring buffer capture up. Will start trigger if first device and appropriate. What: /sys/.../ring_buffer[m]/alignment Description: Minimum data alignment. Scan elements larger than this are aligned to the nearest power of 2 times this. (may not be true in weird hardware ring buffers that pack data well) So an example, adis16350 /sys/class/iio contains device0 accel_scale (applies to all accel channels) accel_x_raw (the raw reading) accel_x_calibbias (calibration value - in reg XACCEL_OFF accel_x_raw_offset assumed to be 0 so not provided). accel_y_raw accel_y_calibbias accel_z_raw accel_z_calibbias gyro_scale gyro_x_raw gyro_x_calibbias gyro_y_raw gyro_x_calibbias gyro_z_raw gyro_z_calbbias volt_0_raw volt_0_scale volt_supply_raw volt_supply_scale temp_gyrox_raw (These are somewhat unusual!) temp_scale temp_offset temp_gyroy_raw temp_gyroz_raw frequency (applies even when trigger not running) //some stuff that may not generalise... auto_bias_calib auto_bias_calib_precision restore_factory gyro_compensate_accel accel_origin_align //associated trigger can be navigated to via device directory. Also the default //trigger will be set correctly. Not in ring_buffer as that directory may become //dependent on live configurable ring buffer types. (spurious argument?) trigger/ current_trigger ring_buffer0/ ring_access0 dev ring_event0 dev length bps ring_enable alignment scan_elements 00_volt_supply_en 01_gyro_x_en 02_gyro_y_en 03_gyro_z_en 04_accel_x_en 05_accel_y_en 06_accel_z_en 07_temp_gyrox_en 08_temp_gyroy_en 09_temp_gyroz_en 10_volt_0_en gyro_prescision accel_precision volt_0_precision volt_supply_precision temp_precision event_line0/ dev accel_x_thresh_high_en accel_x_thresh_high_value accel_x_thresh_high_period accel_x_thresh_low_en accel_x_thresh_low_value accel_x_thresh_low_period accel_x_roc_high_en accel_x_roc_high_value accel_x_roc_high_period accel_x_roc_low_en accel_x_roc_low_value accel_x_roc_low_period //etc. This may seem overkill but this the only option that I //can think of that generalizes well. Other suggestions welcome! //device specific (may generalize) filtered trigger0/ (adis16350 is providing a data ready trigger) name //there are no other parameters here as the datardy frequency is dependent //on how device is configured. (I think it makes more sense in device). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to email@example.com More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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