Re: [PATCH v1 2/2] HID: HID Sensor: Update document for custom sensor

[Jonathan Cameron <jic23@kernel.org>]

On 05/03/15 16:05, Srinivas Pandruvada wrote:
> Added custom sensor documentation
> 
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Looks good to me.

Acked-by: Jonathan Cameron <jic23@kernel.org>

> ---
>  Documentation/hid/hid-sensor.txt | 79 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 79 insertions(+)
> 
> diff --git a/Documentation/hid/hid-sensor.txt b/Documentation/hid/hid-sensor.txt
> index 948b098..25de1bc 100644
> --- a/Documentation/hid/hid-sensor.txt
> +++ b/Documentation/hid/hid-sensor.txt
> @@ -138,3 +138,82 @@ accelerometer wants to poll X axis value, then it can call this function with
>  the usage id of X axis. HID sensors can provide events, so this is not necessary
>  to poll for any field. If there is some new sample, the core driver will call
>  registered callback function to process the sample.
> +
> +
> +----------
> +
> +HID Custom and generic Sensors
> +
> +HID Sensor specification defines two special sensor usage types. Since they
> +don't represent a standard sensor, it is not possible to define using Linux IIO
> +type interfaces.
> +The purpose of these sensors is to extend the functionality or provide a
> +way to obfuscate the data being communicated by a sensor. Without knowing the
> +mapping between the data and its encapsulated form, it is difficult for
> +an application/driver to determine what data is being communicated by the sensor.
> +This allows some differentiating use cases, where vendor can provide applications.
> +Some common use cases are debug other sensors or to provide some events like
> +keyboard attached/detached or lid open/close.
> +
> +To allow application to utilize these sensors, here they are exported uses sysfs
> +attribute groups, attributes and misc device interface.
> +
> +An example of this representation on sysfs:
> +/sys/devices/pci0000:00/INT33C2:00/i2c-0/i2c-INT33D1:00/0018:8086:09FA.0001/HID-SENSOR-2000e1.6.auto$ tree -R
> +.
> +├── enable_sensor
> +├── feature-0-200316
> +│   ├── feature-0-200316-maximum
> +│   ├── feature-0-200316-minimum
> +│   ├── feature-0-200316-size
> +│   ├── feature-0-200316-unit-expo
> +│   ├── feature-0-200316-units
> +│   └── feature-0-200316-value
> +├── feature-1-200201
> +│   ├── feature-1-200201-maximum
> +│   ├── feature-1-200201-minimum
> +│   ├── feature-1-200201-size
> +│   ├── feature-1-200201-unit-expo
> +│   ├── feature-1-200201-units
> +│   └── feature-1-200201-value
> +├── input-0-200201
> +│   ├── input-0-200201-maximum
> +│   ├── input-0-200201-minimum
> +│   ├── input-0-200201-size
> +│   ├── input-0-200201-unit-expo
> +│   ├── input-0-200201-units
> +│   └── input-0-200201-value
> +├── input-1-200202
> +│   ├── input-1-200202-maximum
> +│   ├── input-1-200202-minimum
> +│   ├── input-1-200202-size
> +│   ├── input-1-200202-unit-expo
> +│   ├── input-1-200202-units
> +│   └── input-1-200202-value
> +
> +Here there is a custom sensors with four fields, two feature and two inputs.
> +Each field is represented by a set of attributes. All fields except the "value"
> +are read only. The value field is a RW field.
> +Example
> +/sys/bus/platform/devices/HID-SENSOR-2000e1.6.auto/feature-0-200316$ grep -r . *
> +feature-0-200316-maximum:6
> +feature-0-200316-minimum:0
> +feature-0-200316-size:1
> +feature-0-200316-unit-expo:0
> +feature-0-200316-units:25
> +feature-0-200316-value:1
> +
> +How to enable such sensor?
> +By default sensor can be power gated. To enable sysfs attribute "enable" can be
> +used.
> +$ echo 1 > enable_sensor
> +
> +Once enabled and powered on, sensor can report value using HID reports.
> +These reports are pushed using misc device interface in a FIFO order.
> +/dev$ tree | grep HID-SENSOR-2000e1.6.auto
> +│   ├── 10:53 -> ../HID-SENSOR-2000e1.6.auto
> +├── HID-SENSOR-2000e1.6.auto
> +
> +Each reports can be of variable length preceded by a header. This header
> +consist of a 32 bit usage id of the report and 32 bit length field of raw
> +data. The actual report raw data follows this header.
> 

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