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staging: comedi: introduce some sample size manipulation functions

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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@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ian Abbott 2014-10-23 13:47:51 +01:00 committed by Greg Kroah-Hartman
parent 7885b070b8
commit bf33eb4b4f
1 changed files with 59 additions and 4 deletions
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63
drivers/staging/comedi/comedidev.h
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@ -413,12 +413,67 @@ 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);
}
/*