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.. -*- coding: utf-8; mode: rst -*-
.. _lirc_ioctl:
**************
LIRC ioctl fop
**************
The LIRC device's ioctl definition is bound by the ioctl function
definition of struct file_operations, leaving us with an unsigned int
for the ioctl command and an unsigned long for the arg. For the purposes
of ioctl portability across 32-bit and 64-bit, these values are capped
to their 32-bit sizes.
The following ioctls can be used to change specific hardware settings.
In general each driver should have a default set of settings. The driver
implementation is expected to re-apply the default settings when the
device is closed by user-space, so that every application opening the
device can rely on working with the default settings initially.
LIRC_GET_FEATURES
Obviously, get the underlying hardware device's features. If a
driver does not announce support of certain features, calling of the
corresponding ioctls is undefined.
LIRC_GET_SEND_MODE
Get supported transmit mode. Only LIRC_MODE_PULSE is supported by
lircd.
LIRC_GET_REC_MODE
Get supported receive modes. Only LIRC_MODE_MODE2 and
LIRC_MODE_LIRCCODE are supported by lircd.
LIRC_GET_SEND_CARRIER
Get carrier frequency (in Hz) currently used for transmit.
LIRC_GET_REC_CARRIER
Get carrier frequency (in Hz) currently used for IR reception.
LIRC_{G,S}ET_{SEND,REC}_DUTY_CYCLE
Get/set the duty cycle (from 0 to 100) of the carrier signal.
Currently, no special meaning is defined for 0 or 100, but this
could be used to switch off carrier generation in the future, so
these values should be reserved.
LIRC_GET_REC_RESOLUTION
Some receiver have maximum resolution which is defined by internal
sample rate or data format limitations. E.g. it's common that
signals can only be reported in 50 microsecond steps. This integer
value is used by lircd to automatically adjust the aeps tolerance
value in the lircd config file.
LIRC_GET_M{IN,AX}_TIMEOUT
Some devices have internal timers that can be used to detect when
there's no IR activity for a long time. This can help lircd in
detecting that a IR signal is finished and can speed up the decoding
process. Returns an integer value with the minimum/maximum timeout
that can be set. Some devices have a fixed timeout, in that case
both ioctls will return the same value even though the timeout
cannot be changed.
LIRC_GET_M{IN,AX}_FILTER_{PULSE,SPACE}
Some devices are able to filter out spikes in the incoming signal
using given filter rules. These ioctls return the hardware
capabilities that describe the bounds of the possible filters.
Filter settings depend on the IR protocols that are expected. lircd
derives the settings from all protocols definitions found in its
config file.
LIRC_GET_LENGTH
Retrieves the code length in bits (only for LIRC_MODE_LIRCCODE).
Reads on the device must be done in blocks matching the bit count.
The bit could should be rounded up so that it matches full bytes.
LIRC_SET_{SEND,REC}_MODE
Set send/receive mode. Largely obsolete for send, as only
LIRC_MODE_PULSE is supported.
LIRC_SET_{SEND,REC}_CARRIER
Set send/receive carrier (in Hz).
LIRC_SET_TRANSMITTER_MASK
This enables the given set of transmitters. The first transmitter is
encoded by the least significant bit, etc. When an invalid bit mask
is given, i.e. a bit is set, even though the device does not have so
many transitters, then this ioctl returns the number of available
transitters and does nothing otherwise.
LIRC_SET_REC_TIMEOUT
Sets the integer value for IR inactivity timeout (cf.
LIRC_GET_MIN_TIMEOUT and LIRC_GET_MAX_TIMEOUT). A value of 0
(if supported by the hardware) disables all hardware timeouts and
data should be reported as soon as possible. If the exact value
cannot be set, then the next possible value _greater_ than the
given value should be set.
LIRC_SET_REC_TIMEOUT_REPORTS
Enable (1) or disable (0) timeout reports in LIRC_MODE_MODE2. By
default, timeout reports should be turned off.
LIRC_SET_REC_FILTER_{,PULSE,SPACE}
Pulses/spaces shorter than this are filtered out by hardware. If
filters cannot be set independently for pulse/space, the
corresponding ioctls must return an error and LIRC_SET_REC_FILTER
shall be used instead.
LIRC_SET_MEASURE_CARRIER_MODE
Enable (1)/disable (0) measure mode. If enabled, from the next key
press on, the driver will send LIRC_MODE2_FREQUENCY packets. By
default this should be turned off.
LIRC_SET_REC_{DUTY_CYCLE,CARRIER}_RANGE
To set a range use
LIRC_SET_REC_DUTY_CYCLE_RANGE/LIRC_SET_REC_CARRIER_RANGE
with the lower bound first and later
LIRC_SET_REC_DUTY_CYCLE/LIRC_SET_REC_CARRIER with the upper
bound.
LIRC_NOTIFY_DECODE
This ioctl is called by lircd whenever a successful decoding of an
incoming IR signal could be done. This can be used by supporting
hardware to give visual feedback to the user e.g. by flashing a LED.
LIRC_SETUP_{START,END}
Setting of several driver parameters can be optimized by
encapsulating the according ioctl calls with
LIRC_SETUP_START/LIRC_SETUP_END. When a driver receives a
LIRC_SETUP_START ioctl it can choose to not commit further setting
changes to the hardware until a LIRC_SETUP_END is received. But
this is open to the driver implementation and every driver must also
handle parameter changes which are not encapsulated by
LIRC_SETUP_START and LIRC_SETUP_END. Drivers can also choose to
ignore these ioctls.
LIRC_SET_WIDEBAND_RECEIVER
Some receivers are equipped with special wide band receiver which is
intended to be used to learn output of existing remote. Calling that
ioctl with (1) will enable it, and with (0) disable it. This might
be useful of receivers that have otherwise narrow band receiver that
prevents them to be used with some remotes. Wide band receiver might
also be more precise On the other hand its disadvantage it usually
reduced range of reception. Note: wide band receiver might be
implictly enabled if you enable carrier reports. In that case it
will be disabled as soon as you disable carrier reports. Trying to
disable wide band receiver while carrier reports are active will do
nothing.
.. _lirc_dev_errors:
Return Value
============
On success 0 is returned, on error -1 and the ``errno`` variable is set
appropriately. The generic error codes are described at the
:ref:`Generic Error Codes <gen-errors>` chapter.
|
