diff options
Diffstat (limited to 'Documentation/ABI/testing/sysfs-bus-iio')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-bus-iio | 30 |
1 files changed, 29 insertions, 1 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio index a9d51810a3ba..df42bed09f25 100644 --- a/Documentation/ABI/testing/sysfs-bus-iio +++ b/Documentation/ABI/testing/sysfs-bus-iio @@ -15,6 +15,7 @@ Description: 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. X is the IIO index of the trigger. @@ -65,6 +66,7 @@ Contact: linux-iio@vger.kernel.org Description: When the internal sampling clock can only take a specific set of frequencies, we can specify the available values with: + - a small discrete set of values like "0 2 4 6 8" - a range with minimum, step and maximum frequencies like "[min step max]" @@ -665,6 +667,7 @@ Description: <type>[Y][_name]_<raw|input>_thresh_falling_value may take different values, but the device can only enable both thresholds or neither. + Note the driver will assume the last p events requested are to be enabled where p is how many it supports (which may vary depending on the exact set requested. So if you want to be @@ -719,6 +722,7 @@ Description: <type>[Y][_name]_<raw|input>_roc_falling_value may take different values, but the device can only enable both rate of change thresholds or neither. + Note the driver will assume the last p events requested are to be enabled where p is however many it supports (which may vary depending on the exact set requested. So if you want to be @@ -774,9 +778,11 @@ Description: Specifies the value of threshold that the device is comparing against for the events enabled by <type>Y[_name]_thresh[_rising|falling]_en. + If separate attributes exist for the two directions, but direction is not specified for this attribute, then a single threshold value applies to both directions. + The raw or input element of the name indicates whether the value is in raw device units or in processed units (as _raw and _input do on sysfs direct channel read attributes). @@ -859,6 +865,7 @@ Description: If separate attributes exist for the two directions, but direction is not specified for this attribute, then a single hysteresis value applies to both directions. + For falling events the hysteresis is added to the _value attribute for this event to get the upper threshold for when the event goes back to normal, for rising events the hysteresis is subtracted from the _value @@ -905,6 +912,7 @@ Description: Specifies the value of rate of change threshold that the device is comparing against for the events enabled by <type>[Y][_name]_roc[_rising|falling]_en. + If separate attributes exist for the two directions, but direction is not specified for this attribute, then a single threshold value applies to both directions. @@ -1304,6 +1312,7 @@ Description: Proximity measurement indicating that some object is near the sensor, usually by observing reflectivity of infrared or ultrasound emitted. + Often these sensors are unit less and as such conversion to SI units is not possible. Higher proximity measurements indicate closer objects, and vice versa. Units after @@ -1449,9 +1458,12 @@ Contact: linux-iio@vger.kernel.org Description: A single positive integer specifying the maximum number of scan elements to wait for. + Poll will block until the watermark is reached. + Blocking read will wait until the minimum between the requested read amount or the low water mark is available. + Non-blocking read will retrieve the available samples from the buffer even if there are less samples then watermark level. This allows the application to block on poll with a timeout and read @@ -1480,11 +1492,13 @@ Description: device settings allows it (e.g. if a trigger is set that samples data differently that the hardware fifo does then hardware fifo will not enabled). + If the hardware fifo is enabled and the level of the hardware fifo reaches the hardware fifo watermark level the device will flush its hardware fifo to the device buffer. Doing a non blocking read on the device when no samples are present in the device buffer will also force a flush. + When the hardware fifo is enabled there is no need to use a trigger to use buffer mode since the watermark settings guarantees that the hardware fifo is flushed to the device @@ -1522,6 +1536,7 @@ Description: A single positive integer specifying the minimum watermark level for the hardware fifo of this device. If the device does not have a hardware fifo this entry is not present. + If the user sets buffer/watermark to a value less than this one, then the hardware watermark will remain unset. @@ -1532,6 +1547,7 @@ Description: A single positive integer specifying the maximum watermark level for the hardware fifo of this device. If the device does not have a hardware fifo this entry is not present. + If the user sets buffer/watermark to a value greater than this one, then the hardware watermark will be capped at this value. @@ -1543,6 +1559,7 @@ Description: levels for the hardware fifo. This entry is optional and if it is not present it means that all the values between hwfifo_watermark_min and hwfifo_watermark_max are supported. + If the user sets buffer/watermark to a value greater than hwfifo_watermak_min but not equal to any of the values in this list, the driver will chose an appropriate value for the @@ -1604,7 +1621,8 @@ KernelVersion: 4.1.0 Contact: linux-iio@vger.kernel.org Description: '1' (enable) or '0' (disable) specifying the enable - of heater function. Same reading values apply + of heater function. Same reading values apply. + This ABI is especially applicable for humidity sensors to heatup the device and get rid of any condensation in some humidity environment @@ -1627,17 +1645,21 @@ Description: Mounting matrix for IIO sensors. This is a rotation matrix which informs userspace about sensor chip's placement relative to the main hardware it is mounted on. + Main hardware placement is defined according to the local reference frame related to the physical quantity the sensor measures. + Given that the rotation matrix is defined in a board specific way (platform data and / or device-tree), the main hardware reference frame definition is left to the implementor's choice (see below for a magnetometer example). + Applications should apply this rotation matrix to samples so that when main hardware reference frame is aligned onto local reference frame, then sensor chip reference frame is also perfectly aligned with it. + Matrix is a 3x3 unitary matrix and typically looks like [0, 1, 0; 1, 0, 0; 0, 0, -1]. Identity matrix [1, 0, 0; 0, 1, 0; 0, 0, 1] means sensor chip and main hardware @@ -1646,8 +1668,10 @@ Description: For example, a mounting matrix for a magnetometer sensor informs userspace about sensor chip's ORIENTATION relative to the main hardware. + More specifically, main hardware orientation is defined with respect to the LOCAL EARTH GEOMAGNETIC REFERENCE FRAME where : + * Y is in the ground plane and positive towards magnetic North ; * X is in the ground plane, perpendicular to the North axis and positive towards the East ; @@ -1656,13 +1680,16 @@ Description: An implementor might consider that for a hand-held device, a 'natural' orientation would be 'front facing camera at the top'. The main hardware reference frame could then be described as : + * Y is in the plane of the screen and is positive towards the top of the screen ; * X is in the plane of the screen, perpendicular to Y axis, and positive towards the right hand side of the screen ; * Z is perpendicular to the screen plane and positive out of the screen. + Another example for a quadrotor UAV might be : + * Y is in the plane of the propellers and positive towards the front-view camera; * X is in the plane of the propellers, perpendicular to Y axis, @@ -1704,6 +1731,7 @@ Description: This interface is deprecated; please use the Counter subsystem. A list of possible counting directions which are: + - "up" : counter device is increasing. - "down": counter device is decreasing. |