2012-06-27 01:12:33

by Hartley Sweeten

Subject: [PATCH 36/36] staging: comedi: cb_pcidas: cleanup dac08_write()

Reverse the logic of the test against the cached value so that
the function only has one exit point.

Make the logic of the dac write a bit clearer by create a local
variable for the address used in the outw() calls and masking the
value to write and setting the enable bits before doing the outw()
calls. Add a comment just to make sure it's clear.

Also, add a comment about the 'return 1;'. This should be
insn->n which is the number of data parameters used to do the
dac08_write_insn() but the insn is not a parameter to this
function.

Signed-off-by: H Hartley Sweeten <[email protected]>
Cc: Ian Abbott <[email protected]>
Cc: Frank Mori Hess <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
---
drivers/staging/comedi/drivers/cb_pcidas.c | 28 +++++++++++++++-------------
1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/drivers/staging/comedi/drivers/cb_pcidas.c b/drivers/staging/comedi/drivers/cb_pcidas.c
index 1479325..3ba75af 100644
--- a/drivers/staging/comedi/drivers/cb_pcidas.c
+++ b/drivers/staging/comedi/drivers/cb_pcidas.c
@@ -662,23 +662,25 @@ static int caldac_read_insn(struct comedi_device *dev,
static int dac08_write(struct comedi_device *dev, unsigned int value)
{
struct cb_pcidas_private *devpriv = dev->private;
+ unsigned long cal_reg;

- if (devpriv->dac08_value == value)
- return 1;
+ if (devpriv->dac08_value != value) {
+ devpriv->dac08_value = value;

- devpriv->dac08_value = value;
+ cal_reg = devpriv->control_status + CALIBRATION_REG;

- outw(cal_enable_bits(dev) | (value & 0xff),
- devpriv->control_status + CALIBRATION_REG);
- udelay(1);
- outw(cal_enable_bits(dev) | SELECT_DAC08_BIT | (value & 0xff),
- devpriv->control_status + CALIBRATION_REG);
- udelay(1);
- outw(cal_enable_bits(dev) | (value & 0xff),
- devpriv->control_status + CALIBRATION_REG);
- udelay(1);
+ value &= 0xff;
+ value |= cal_enable_bits(dev);

- return 1;
+ /* latch the new value into the caldac */
+ outw(value, cal_reg);
+ udelay(1);
+ outw(value | SELECT_DAC08_BIT, cal_reg);
+ udelay(1);
+ outw(value, cal_reg);
+ udelay(1);
+ }
+ return 1; /* insn->n */
}

static int dac08_write_insn(struct comedi_device *dev,
--
1.7.11

2012-06-27 09:44:44

by Ian Abbott

Subject: Re: [PATCH 36/36] staging: comedi: cb_pcidas: cleanup dac08_write()

On 2012-06-27 02:12, H Hartley Sweeten wrote:
> Reverse the logic of the test against the cached value so that
> the function only has one exit point.
>
> Make the logic of the dac write a bit clearer by create a local
> variable for the address used in the outw() calls and masking the
> value to write and setting the enable bits before doing the outw()
> calls. Add a comment just to make sure it's clear.
>
> Also, add a comment about the 'return 1;'. This should be
> insn->n which is the number of data parameters used to do the
> dac08_write_insn() but the insn is not a parameter to this
> function.

It's probably better to make dac08_write() return void and return 1 in
dac08_write_insn().

Actually, I think dac08_write_insn() ought to call dac08_write() in a
loop, iterating over data[] and return insn->n. That's what the
INSN_WRITE instruction is meant to do although it's not implemented all
that consistently by the drivers.

--
-=( Ian Abbott @ MEV Ltd. E-mail: <[email protected]> )=-
-=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=-