\# Author Andy Pugh
\# Issued under the terms of the GPL v2 License or any later version

.TH hm2_bspi_set_write_function "3hm2" "2011-05-31" "LinuxCNC Documentation" "Hostmot2"
.SH NAME

hm2_bspi_set_write_function \- Register a function to handle the tram write phase
of a hostmot2 buffered SPI driver. 
.SH SYNTAX
.nf
.B #include <hostmot2-serial.h>
.HP
int hm2_bspi_set_write_function(char *name, void *func, void *subdata)

.SH DESCRIPTION
\fBhm2_bspi_set_write_function\fR registers a function in an external driver
to be called every time that the main Hostmot2
driver calls the generic "prepare_tram_write" functions. 
The names of the available channels are printed with rtapi_print_msg during the
driver loading process and take the form:
.RS
hm2_<board name>.<board index>.bspi.<index>
.RE
For example hm2_5i23.0.bspi.0.

"func" should be a pointer to a function in the sub driver which is to be
called to process the pins into BSPI write registers prior to the regular TRAM
write phase. The function must take a single argument, a pointer to an
individual instance of the internal driver. If defined in comp then the 
function must \fBnot\fP use the FUNCTION() convenience macro, and the argument
to the function in the definition  must \fBalways\fP be (struct state *inst).

"subdata" is a pointer to the driver instance internal data. In the case of a
driver written in comp this will always be "inst" in the function call.

If using comp then the call to this function should be anywhere in the
EXTRA_SETUP code. 

.SH REALTIME CONSIDERATIONS
Call only from realtime init code, not from user space or realtime code.

.SH RETURN VALUE
Returns 0 on success and \-1 on failure.

.SH SEE ALSO
\fBhm2_allocate_bspi_tram(3hm2)\fR,
\fBhm2_bspi_set_read_function(3hm2)\fR,
\fBhm2_bspi_setup_chan(3hm2)\fR,
\fBhm2_bspi_write_chan(3hm2)\fR,
\fBhm2_tram_add_bspi_frame(3hm2)\fR,
src/hal/drivers mesa_7i65.comp in the LinuxCNC source distribution.
