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staging: comedi: usbdux: simplify initializing the ao urb transfer_buffer

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Remove the ugly casting of datap to the ao urb->transfer_buffer. The format
of the data in the buffer is simply.

  [0] = # of channels to update (s->async->cmd.chanlist.len)
  [1] = lsb of value for 1st channel to update
  [2] = msb of value for 1st channel to update
  [3] = 1st channel to update (depvriv->dac_commands[0])

If more than 1 channel is to be updated they are simply added to the buffer:

  [4] = lsb of value for 2st channel to update
  [5] = msb of value for 2st channel to update
  [6] = 1st channel to update (depvriv->dac_commands[1])

etc.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Reviewed-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
H Hartley Sweeten 2013-07-25 16:10:25 -07:00 • committed by Greg Kroah-Hartman
parent a998a3db53
commit c769f85e27
1 changed files with 10 additions and 9 deletions
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19
drivers/staging/comedi/drivers/usbdux.c
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@ -425,8 +425,10 @@ static void usbduxsub_ao_isoc_irq(struct urb *urb)
struct comedi_device *dev = urb->context;
struct comedi_subdevice *s = dev->write_subdev;
struct usbdux_private *devpriv = dev->private;
int i, ret;
int8_t *datap;
int len;
int ret;
int i;
switch (urb->status) {
case 0:
@ -484,9 +486,11 @@ static void usbduxsub_ao_isoc_irq(struct urb *urb)
return;
}
}
/* transmit data to the USB bus */
((uint8_t *) (urb->transfer_buffer))[0] =
s->async->cmd.chanlist_len;
datap = urb->transfer_buffer;
len = s->async->cmd.chanlist_len;
*datap++ = len;
for (i = 0; i < s->async->cmd.chanlist_len; i++) {
unsigned int chan = devpriv->dac_commands[i];
short val;
@ -498,12 +502,9 @@ static void usbduxsub_ao_isoc_irq(struct urb *urb)
COMEDI_CB_OVERFLOW);
}
/* pointer to the DA */
datap =
(&(((int8_t *) urb->transfer_buffer)[i * 3 + 1]));
/* get the data from comedi */
datap[0] = val;
datap[1] = val >> 8;
datap[2] = chan;
*datap++ = val & 0xff;
*datap++ = (val >> 8) & 0xff;
*datap++ = chan;
devpriv->ao_readback[chan] = val;
s->async->events |= COMEDI_CB_BLOCK;