6.4.2. LIRC write()¶
6.4.2.1. Name¶
lirc-write - Write to a LIRC device
6.4.2.3. Arguments¶
fd- File descriptor returned by
open(). buf- Buffer with data to be written
count- Number of bytes at the buffer
6.4.2.4. Description¶
write() writes up to count bytes to the device
referenced by the file descriptor fd from the buffer starting at
buf.
The exact format of the data depends on what mode a driver is in, use ioctl LIRC_GET_FEATURES to get the supported modes and use ioctls LIRC_GET_SEND_MODE and LIRC_SET_SEND_MODE set the mode.
When in LIRC_MODE_PULSE mode, the data written to
the chardev is a pulse/space sequence of integer values. Pulses and spaces
are only marked implicitly by their position. The data must start and end
with a pulse, therefore, the data must always include an uneven number of
samples. The write function blocks until the data has been transmitted
by the hardware. If more data is provided than the hardware can send, the
driver returns EINVAL.
When in LIRC_MODE_SCANCODE mode, one
struct lirc_scancode must be written to the chardev at a time, else
EINVAL is returned. Set the desired scancode in the scancode member,
and the IR protocol in the
rc_proto: member. All other members must be
set to 0, else EINVAL is returned. If there is no protocol encoder
for the protocol or the scancode is not valid for the specified protocol,
EINVAL is returned. The write function blocks until the scancode
is transmitted by the hardware.
6.4.2.5. Return Value¶
On success, the number of bytes written is returned. It is not an error if
this number is smaller than the number of bytes requested, or the amount
of data required for one frame. On error, -1 is returned, and the errno
variable is set appropriately. The generic error codes are described at the
Generic Error Codes chapter.