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demo/mmap: check subdevice exists and supports 'read' commands

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Check the subdevice actually exists and that it claims to support 'read'
commands (SDF_CMD_READ subdevice flag set), bailing out early if not.
This commit is contained in:
Ian Abbott 2016-11-08 14:29:58 +00:00
parent ad70295bb4
commit facb713cd8
1 changed files with 14 additions and 0 deletions
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14
demo/mmap.c
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@ -70,6 +70,20 @@ int main(int argc, char *argv[])
fprintf(stderr, "defaulted to subdevice %d\n", options.subdevice);
}
/* Check subdevice exists. */
ret = comedi_get_n_subdevices(dev);
if(ret <= options.subdevice){
fprintf(stderr, "subdevice %d does not exist\n", options.subdevice);
exit(1);
}
/* Check subdevice supports 'read' commands. */
ret = comedi_get_subdevice_flags(dev, options.subdevice);
if(ret < 0 || !(ret & SDF_CMD_READ)) {
fprintf(stderr, "subdevice %d does not support 'read' commands\n", options.subdevice);
exit(1);
}
ret = comedi_get_buffer_size(dev, options.subdevice);
if(ret < 0){
comedi_perror("comedi_get_buffer_size");