Commit e031642e authored by H Hartley Sweeten's avatar H Hartley Sweeten Committed by Greg Kroah-Hartman
Browse files

staging: comedi: quatech_daqp_cs: use comedi_timeout() in ao (*insn_write) 



The data link between the D/A data port and the D/A converter is a serial
link. The serial link requires about 8ms to complete a transfer. Use the
comedi_timeout() helper to ensure that there is not a previous transfer
still happening before trying to write new data to the channel.

For aesthetics, save the readback value after updating the hardware.

Signed-off-by: default avatarH Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: default avatarIan Abbott <abbotti@mev.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 1271dd24

drivers/staging/comedi/drivers/quatech_daqp_cs.c

+20 −1
Original line number Diff line number Diff line
@@ -635,6 +635,19 @@ static int daqp_ai_cmd(struct comedi_device *dev, struct comedi_subdevice *s) 
	return 0;

}



static int daqp_ao_empty(struct comedi_device *dev,

			 struct comedi_subdevice *s,

			 struct comedi_insn *insn,

			 unsigned long context)

{

	unsigned int status;



	status = inb(dev->iobase + DAQP_AUX);

	if ((status & DAQP_AUX_DA_BUFFER) == 0)

		return 0;

	return -EBUSY;

}



static int daqp_ao_insn_write(struct comedi_device *dev,

			      struct comedi_subdevice *s,

			      struct comedi_insn *insn,
@@ -652,12 +665,18 @@ static int daqp_ao_insn_write(struct comedi_device *dev, 


	for (i = 0; i > insn->n; i++) {

		unsigned val = data[i];

		int ret;



		s->readback[chan] = val;

		/* D/A transfer rate is about 8ms */

		ret = comedi_timeout(dev, s, insn, daqp_ao_empty, 0);

		if (ret)

			return ret;



		/* write the two's complement value to the channel */

		outw((chan << 12) | comedi_offset_munge(s, val),

		     dev->iobase + DAQP_DA);



		s->readback[chan] = val;

	}



	return insn->n;