staging: comedi: cb_pcidas: cleanup dac08_write()

PATCH In review H Hartley Sweeten 2 participants 2 messages Jun 27, 2012 Staging

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H Hartley Sweeten

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2012-06-27 01:12 UTC #0 lore raw

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(-)

drivers/staging/comedi/drivers/cb_pcidas.c +15 ~~-13~~

index 1479325..3ba75af 100644
@@ -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,

Signature · 1 line

1.7.11

Ian Abbott

2012-06-27 09:44 UTC #1 lore raw

Quoted 8 lines · H Hartley Sweeten

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.

Quoted 4 lines

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.

Signature · 2 lines

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