staging:iio: ABI documentation (partial)

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

drivers/staging/iio/Documentation/sysfs-class-iio

+
+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)
+