Introduce a few static inline helper functions:
`comedi_bytes_per_sample(s)` is the same as the existing
`bytes_per_sample(s)` and determines the size of a comedi sample in
bytes. (`bytes_per_sample(s)` will be removed.)
`comedi_sample_shift(s)` determines the log2 of the comedi sample size,
so it can be used in bit-shift operations to multiply or divide by the
sample size.
`comedi_bytes_to_samples(s, nbytes)` converts a number of bytes to a
number of samples (rounding down).
`comedi_samples_to_bytes(s, nsamples)` converts a number of samples to a
number of bytes.
Signed-off-by: Ian Abbott <abbotti@xxxxxxxxx>
---
drivers/staging/comedi/comedidev.h | 63 +++++++++++++++++++++++++++++++++++---
1 file changed, 59 insertions(+), 4 deletions(-)
diff --git a/drivers/staging/comedi/comedidev.h b/drivers/staging/comedi/comedidev.h
index 1b2bbd5..69cf6fe 100644
--- a/drivers/staging/comedi/comedidev.h
+++ b/drivers/staging/comedi/comedidev.h
@@ -391,12 +391,67 @@ static inline unsigned int comedi_offset_munge(struct comedi_subdevice *s,
return val ^ s->maxdata ^ (s->maxdata >> 1);
}
-static inline unsigned int bytes_per_sample(const struct comedi_subdevice *subd)
+/**
+ * comedi_bytes_per_sample - determine subdevice sample size
+ * @s: comedi_subdevice struct
+ *
+ * The sample size will be 4 (sizeof int) or 2 (sizeof short) depending on
+ * whether the SDF_LSAMPL subdevice flag is set or not.
+ *
+ * Returns the subdevice sample size.
+ */
+static inline unsigned int comedi_bytes_per_sample(struct comedi_subdevice *s)
{
- if (subd->subdev_flags & SDF_LSAMPL)
- return sizeof(unsigned int);
+ return s->subdev_flags & SDF_LSAMPL ? sizeof(int) : sizeof(short);
+}
- return sizeof(short);
+/* to be removed */
+static inline unsigned int bytes_per_sample(struct comedi_subdevice *s)
+{
+ return comedi_bytes_per_sample(s);
+}
+
+/**
+ * comedi_sample_shift - determine log2 of subdevice sample size
+ * @s: comedi_subdevice struct
+ *
+ * The sample size will be 4 (sizeof int) or 2 (sizeof short) depending on
+ * whether the SDF_LSAMPL subdevice flag is set or not. The log2 of the
+ * sample size will be 2 or 1 and can be used as the right operand of a
+ * bit-shift operator to multiply or divide something by the sample size.
+ *
+ * Returns log2 of the subdevice sample size.
+ */
+static inline unsigned int comedi_sample_shift(struct comedi_subdevice *s)
+{
+ return s->subdev_flags & SDF_LSAMPL ? 2 : 1;
+}
+
+/**
+ * comedi_bytes_to_samples - converts a number of bytes to a number of samples
+ * @s: comedi_subdevice struct
+ * @nbytes: number of bytes
+ *
+ * Returns the number of bytes divided by the subdevice sample size.
+ */
+static inline unsigned int comedi_bytes_to_samples(struct comedi_subdevice *s,
+ unsigned int nbytes)
+{
+ return nbytes >> comedi_sample_shift(s);
+}
+
+/**
+ * comedi_samples_to_bytes - converts a number of samples to a number of bytes
+ * @s: comedi_subdevice struct
+ * @nsamples: number of samples
+ *
+ * Returns the number of samples multiplied by the subdevice sample size.
+ * Does not check for arithmetic overflow.
+ */
+static inline unsigned int comedi_samples_to_bytes(struct comedi_subdevice *s,
+ unsigned int nsamples)
+{
+ return nsamples << comedi_sample_shift(s);
}
/*
--
2.1.1
_______________________________________________
devel mailing list
devel@xxxxxxxxxxxxxxxxxxxxxx
http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
