ssize_t
LSM303D::mag_read(struct file *filp, char *buffer, size_t buflen)
{
unsigned count = buflen / sizeof(struct mag_report);
mag_report *mrb = reinterpret_cast<mag_report *>(buffer);
int ret = 0;
/* buffer must be large enough */
if (count < 1)
return -ENOSPC;
/* if automatic measurement is enabled */
if (_call_mag_interval > 0) {
/*
* While there is space in the caller's buffer, and reports, copy them.
*/
while (count--) {
if (_mag_reports->get(mrb)) {
ret += sizeof(*mrb);
mrb++;
}
}
/* if there was no data, warn the caller */
return ret ? ret : -EAGAIN;
}
/* manual measurement */
_mag_reports->flush();
_mag->measure();
/* measurement will have generated a report, copy it out */
if (_mag_reports->get(mrb))
ret = sizeof(*mrb);
return ret;
}
