staging:iio: ABI documentation (partial)

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/staging/iio/Documentation/sysfs-class-iio b/drivers/staging/iio/Documentation/sysfs-class-iio
new file mode 100644 (file)
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+
+What:          /sys/bus/iio/devices/device[n]
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Hardware chip or device accessed by on communication port.
+               Corresponds to a grouping of sensor channels.
+
+What:          /sys/bus/iio/devices/trigger[n]
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               An event driven driver of data capture to an in kernel buffer.
+               May be provided by a device driver that also has an IIO device
+               based on hardware generated events (e.g. data ready) or
+               provided by a separate driver for other hardware (e.g.
+               periodic timer, gpio or high resolution timer).
+               Contains trigger type specific elements. These do not
+               generalize well and hence are not documented in this file.
+
+What:          /sys/bus/iio/devices/device[n]:buffer
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Link to /sys/class/iio/device[n]/device[n]:buffer. n indicates the
+               device with which this buffer buffer is associated.
+
+What:          /sys/.../device[n]/name
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Description of the physical chip / device. Typically a part
+               number.
+
+What:          /sys/.../device[n]/sampling_frequency
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Some devices have internal clocks.  This parameter sets the
+               resulting sampling frequency.  In many devices this
+               parameter has an effect on input filters etc rather than
+               simply controlling when the input is sampled.  As this
+               effects datardy triggers, hardware buffers and the sysfs
+               direct access interfaces, it may be found in any of the
+               relevant directories.  If it effects all of the above
+               then it is to be found in the base device directory as here.
+
+What:          /sys/.../device[n]/sampling_frequency_available
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               When the internal sampling clock can only take a small
+               discrete set of values, this file lists those availale.
+
+What:          /sys/.../device[n]/in[_name][m]_raw
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+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 in which case the file is in_supply_raw).
+
+What:          /sys/.../device[n]/in[_name][m]_offset
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               If known for a device, offset to be added to in[m]_raw prior
+               to scaling by volt[m]_scale in order to obtain voltage in
+               millivolts.  Not present if the offset is always 0 or unknown.
+               If m is not present, then voltage offset applies to all in
+               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, typically adjusted by
+               using some hardware supported calibration procedure.
+
+What:          /sys/.../device[n]/in[_name][m]_offset_available
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+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/.../device[n]/in[_name][m]_offset_[min|max]
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               If a more or less continuous range of voltage offsets are supported
+               then these specify the minimum and maximum.  If shared by all
+               in channels then m is not present.
+
+What:          /sys/.../device[n]/in[_name][m]_calibbias
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Hardware applied calibration offset. (assumed to fix production
+               inaccuracies)
+
+What           /sys/.../device[n]/in[_name][m]_calibscale
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Hardware applied calibration scale factor. (assumed to fix production
+               inaccuracies)
+
+What:          /sys/.../device[n]/in[_name][m]_scale
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+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 millivolts.  If shared across all in channels then m is not present.
+
+What:          /sys/.../device[n]/in[m]-in[o]_raw
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Raw (unscaled) differential voltage measurement equivalent to
+               channel m - channel o where these channel numbers apply to the physically
+               equivalent inputs when non differential readings are separately available.
+               In differential only parts, then all that is required is a consistent
+               labelling.
+
+What:          /sys/.../device[n]/accel[_x|_y|_z][m]_raw
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+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 in[m].
+               Units after application of scale and offset are m/s^2.
+
+What:          /sys/.../device[n]/gyro[_x|_y|_z][m]_raw
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+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 in[m].
+
+What:          /sys/.../device[n]/mag[_x|_y|_z][m]_raw
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+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 in[m].
+
+What:          /sys/.../device[n]/device[n]:event[m]
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+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/.../device[n]:event[m]/dev
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               major:minor character device numbers for the event line.
+
+Taking accel_x0 as an example
+
+What:          /sys/.../device[n]:event[m]/accel_x0_thresh[_high|_low]_en
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+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/.../device[n]:event[m]/accel_x0_roc[_high|_low]_en
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Same as above but based on the first differential of the value.
+
+
+What:          /sys/.../device[n]:event[m]/accel_x0[_thresh|_roc][_high|_low]_period
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+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/.../device[n]:event[m]/accel_x0[_thresh|_roc][_high|_low]_value
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               The actual value of the threshold in raw device units obtained by
+                reverse application of scale and offfset to the acceleration in m/s^2.
+
+What:          /sys/.../device[n]/scan_elements
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Directory containing interfaces for elements that will be captured
+               for a single triggered sample set in the buffer.
+
+What:          /sys/.../device[n]/scan_elements/[m]_accel_x0_en
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+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/.../device[n]/scan_elements/accel[_x0]_precision
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Scan element precision within the buffer. Note that the
+               data alignment must restrictions must be read from within
+               buffer to work out full data alignment for data read
+               via buffer_access chrdev. _x0 dropped if shared across all
+               acceleration channels.
+
+What:          /sys/.../device[n]/scan_elements/accel[_x0]_shift
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               A bit shift (to right) that must be applied prior to
+               extracting the bits specified by accel[_x0]_precision.
+
+What:          /sys/.../device[n]/device[n]:buffer:event/dev
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Buffer for device n event character device major:minor numbers.
+
+What:          /sys/.../device[n]/device[n]:buffer:access/dev
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Buffer for device n access character device o major:minor numbers.
+
+What:          /sys/.../device[n]:buffer/trigger
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               The name of the trigger source being used, as per string given
+               in /sys/class/iio/trigger[n]/name.
+
+What:          /sys/.../device[n]:buffer/length
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Number of scans contained by the buffer.
+
+What:          /sys/.../device[n]:buffer/bps
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Bytes per scan.  Due to alignment fun, the scan may be larger
+               than implied directly by the scan_element parameters.
+
+What:          /sys/.../device[n]:buffer/enable
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+Description:
+               Actually start the buffer capture up.  Will start trigger
+               if first device and appropriate.
+
+What:          /sys/.../device[n]:buffer/alignment
+KernelVersion: 2.6.35
+Contact:       linux-iio@vger.kernel.org
+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 buffers that pack data well)
+