The `DAS08_MUX_MASK` macro is a bitmask for the control register
corresponding to the analog input multiplexor channel selection bits.
Rename it to `DAS08_CONTROL_MUX_MASK` and add a comment. Note that the
current setting of the multiplexor can also be read from the same bit
positions in the status register, but the driver does not use it. Add a
comment to that effect.
The `DAS08_MUX(x)` macro takes an analog input channel number and
returns the corresponding analog input multiplexor channel selection
bits for the control register. Rename it to `DAS08_CONTROL_MUX(x)` and
add a comment.
Signed-off-by: Ian Abbott <abbo...@mev.co.uk>
---
drivers/staging/comedi/drivers/das08.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/drivers/staging/comedi/drivers/das08.c
b/drivers/staging/comedi/drivers/das08.c
index b43bc2d..f0ee617 100644
--- a/drivers/staging/comedi/drivers/das08.c
+++ b/drivers/staging/comedi/drivers/das08.c
@@ -68,8 +68,12 @@
/* digital inputs (not "JR" boards) */
#define DAS08_STATUS_DI(x) (((x) & 0x70) >> 4)
#define DAS08_CONTROL_REG 0x02 /* (W) control */
-#define DAS08_MUX_MASK 0x7
-#define DAS08_MUX(x) ((x) & DAS08_MUX_MASK)
+/*
+ * Note: The AI multiplexor channel can also be read from status register using
+ * the same mask.
+ */
+#define DAS08_CONTROL_MUX_MASK 0x7 /* multiplexor channel mask */
+#define DAS08_CONTROL_MUX(x) ((x) & DAS08_CONTROL_MUX_MASK) /* mux channel */
#define DAS08_INTE (1<<3)
#define DAS08_DO_MASK 0xf0
#define DAS08_OP(x) (((x) << 4) & DAS08_DO_MASK)
@@ -238,8 +242,8 @@ static int das08_ai_rinsn(struct comedi_device *dev, struct
comedi_subdevice *s,
/* set multiplexer */
/* lock to prevent race with digital output */
spin_lock(&dev->spinlock);
- devpriv->do_mux_bits &= ~DAS08_MUX_MASK;
- devpriv->do_mux_bits |= DAS08_MUX(chan);
+ devpriv->do_mux_bits &= ~DAS08_CONTROL_MUX_MASK;
+ devpriv->do_mux_bits |= DAS08_CONTROL_MUX(chan);
outb(devpriv->do_mux_bits, dev->iobase + DAS08_CONTROL_REG);
spin_unlock(&dev->spinlock);
--
2.1.4
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