mirror of
https://github.com/torvalds/linux.git
synced 2024-11-16 09:02:00 +00:00
3f0f4a3f20
Add short documentation for two ALS / proximity chip drivers. Signed-off-by: Samu Onkalo <samu.p.onkalo@nokia.com> Acked-by: Jonathan Cameron <jic23@cam.ac.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
112 lines
3.5 KiB
Plaintext
112 lines
3.5 KiB
Plaintext
Kernel driver apds990x
|
|
======================
|
|
|
|
Supported chips:
|
|
Avago APDS990X
|
|
|
|
Data sheet:
|
|
Not freely available
|
|
|
|
Author:
|
|
Samu Onkalo <samu.p.onkalo@nokia.com>
|
|
|
|
Description
|
|
-----------
|
|
|
|
APDS990x is a combined ambient light and proximity sensor. ALS and proximity
|
|
functionality are highly connected. ALS measurement path must be running
|
|
while the proximity functionality is enabled.
|
|
|
|
ALS produces raw measurement values for two channels: Clear channel
|
|
(infrared + visible light) and IR only. However, threshold comparisons happen
|
|
using clear channel only. Lux value and the threshold level on the HW
|
|
might vary quite much depending the spectrum of the light source.
|
|
|
|
Driver makes necessary conversions to both directions so that user handles
|
|
only lux values. Lux value is calculated using information from the both
|
|
channels. HW threshold level is calculated from the given lux value to match
|
|
with current type of the lightning. Sometimes inaccuracy of the estimations
|
|
lead to false interrupt, but that doesn't harm.
|
|
|
|
ALS contains 4 different gain steps. Driver automatically
|
|
selects suitable gain step. After each measurement, reliability of the results
|
|
is estimated and new measurement is trigged if necessary.
|
|
|
|
Platform data can provide tuned values to the conversion formulas if
|
|
values are known. Otherwise plain sensor default values are used.
|
|
|
|
Proximity side is little bit simpler. There is no need for complex conversions.
|
|
It produces directly usable values.
|
|
|
|
Driver controls chip operational state using pm_runtime framework.
|
|
Voltage regulators are controlled based on chip operational state.
|
|
|
|
SYSFS
|
|
-----
|
|
|
|
|
|
chip_id
|
|
RO - shows detected chip type and version
|
|
|
|
power_state
|
|
RW - enable / disable chip. Uses counting logic
|
|
1 enables the chip
|
|
0 disables the chip
|
|
lux0_input
|
|
RO - measured lux value
|
|
sysfs_notify called when threshold interrupt occurs
|
|
|
|
lux0_sensor_range
|
|
RO - lux0_input max value. Actually never reaches since sensor tends
|
|
to saturate much before that. Real max value varies depending
|
|
on the light spectrum etc.
|
|
|
|
lux0_rate
|
|
RW - measurement rate in Hz
|
|
|
|
lux0_rate_avail
|
|
RO - supported measurement rates
|
|
|
|
lux0_calibscale
|
|
RW - calibration value. Set to neutral value by default.
|
|
Output results are multiplied with calibscale / calibscale_default
|
|
value.
|
|
|
|
lux0_calibscale_default
|
|
RO - neutral calibration value
|
|
|
|
lux0_thresh_above_value
|
|
RW - HI level threshold value. All results above the value
|
|
trigs an interrupt. 65535 (i.e. sensor_range) disables the above
|
|
interrupt.
|
|
|
|
lux0_thresh_below_value
|
|
RW - LO level threshold value. All results below the value
|
|
trigs an interrupt. 0 disables the below interrupt.
|
|
|
|
prox0_raw
|
|
RO - measured proximity value
|
|
sysfs_notify called when threshold interrupt occurs
|
|
|
|
prox0_sensor_range
|
|
RO - prox0_raw max value (1023)
|
|
|
|
prox0_raw_en
|
|
RW - enable / disable proximity - uses counting logic
|
|
1 enables the proximity
|
|
0 disables the proximity
|
|
|
|
prox0_reporting_mode
|
|
RW - trigger / periodic. In "trigger" mode the driver tells two possible
|
|
values: 0 or prox0_sensor_range value. 0 means no proximity,
|
|
1023 means proximity. This causes minimal number of interrupts.
|
|
In "periodic" mode the driver reports all values above
|
|
prox0_thresh_above. This causes more interrupts, but it can give
|
|
_rough_ estimate about the distance.
|
|
|
|
prox0_reporting_mode_avail
|
|
RO - accepted values to prox0_reporting_mode (trigger, periodic)
|
|
|
|
prox0_thresh_above_value
|
|
RW - threshold level which trigs proximity events.
|