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staging: comedi: comedi_buf: factor out common comedi_buf_write_alloc_* code

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The only difference between comedi_buf_write_alloc() and the *_strict()
version is that the *_strict() one will only allocate the chunk if it
can completely fulfill the request.

Factor out the common code and add a flag parameter to indicate the 'strict'
usage. Change the exported functions so they are just wrappers around the
common function.

Cleanup the common function a bit and use the comedi_buf_write_n_available()
helper to determine the number of bytes available.

comedi_buf_write_n_available() is not used outside this module so make it
static. Since the only caller is __comedi_buf_write_alloc(), which will
always have a valid async pointer and already has a memory barrier, we
can remove the unnecessary (async == NULL) test as well as the smp_mb().
Also, the rounding of the sample size can be removed since the caller
does not need it.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
H Hartley Sweeten 2013-01-09 13:27:48 -07:00 committed by Greg Kroah-Hartman
parent 61c9fb0eb0
commit f8f76e909b
2 changed files with 21 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

52
drivers/staging/comedi/comedi_buf.c
View File

@ -159,22 +159,30 @@ void comedi_buf_reset(struct comedi_async *async)
async->events = 0;
}
unsigned int comedi_buf_write_n_available(struct comedi_async *async)
static unsigned int comedi_buf_write_n_available(struct comedi_async *async)
{
unsigned int free_end;
unsigned int nbytes;
unsigned int free_end = async->buf_read_count + async->prealloc_bufsz;
if (async == NULL)
return 0;
return free_end - async->buf_write_alloc_count;
}
free_end = async->buf_read_count + async->prealloc_bufsz;
nbytes = free_end - async->buf_write_alloc_count;
nbytes -= nbytes % bytes_per_sample(async->subdevice);
/* barrier insures the read of buf_read_count in this
query occurs before any following writes to the buffer which
might be based on the return value from this query.
static unsigned int __comedi_buf_write_alloc(struct comedi_async *async,
unsigned int nbytes,
int strict)
{
unsigned int available = comedi_buf_write_n_available(async);
if (nbytes > available)
nbytes = strict ? 0 : available;
async->buf_write_alloc_count += nbytes;
/*
* ensure the async buffer 'counts' are read and updated
* before we write data to the write-alloc'ed buffer space
*/
smp_mb();
return nbytes;
}
@ -182,16 +190,7 @@ unsigned int comedi_buf_write_n_available(struct comedi_async *async)
unsigned int comedi_buf_write_alloc(struct comedi_async *async,
unsigned int nbytes)
{
unsigned int free_end = async->buf_read_count + async->prealloc_bufsz;
if ((int)(async->buf_write_alloc_count + nbytes - free_end) > 0)
nbytes = free_end - async->buf_write_alloc_count;
async->buf_write_alloc_count += nbytes;
/* barrier insures the read of buf_read_count above occurs before
we write data to the write-alloc'ed buffer space */
smp_mb();
return nbytes;
return __comedi_buf_write_alloc(async, nbytes, 0);
}
EXPORT_SYMBOL(comedi_buf_write_alloc);
@ -199,16 +198,7 @@ EXPORT_SYMBOL(comedi_buf_write_alloc);
unsigned int comedi_buf_write_alloc_strict(struct comedi_async *async,
unsigned int nbytes)
{
unsigned int free_end = async->buf_read_count + async->prealloc_bufsz;
if ((int)(async->buf_write_alloc_count + nbytes - free_end) > 0)
nbytes = 0;
async->buf_write_alloc_count += nbytes;
/* barrier insures the read of buf_read_count above occurs before
we write data to the write-alloc'ed buffer space */
smp_mb();
return nbytes;
return __comedi_buf_write_alloc(async, nbytes, 1);
}
/* munging is applied to data by core as it passes between user

1
drivers/staging/comedi/comedidev.h
View File

@ -438,7 +438,6 @@ comedi_to_usb_interface(struct comedi_device *dev)
int comedi_buf_put(struct comedi_async *async, short x);
int comedi_buf_get(struct comedi_async *async, short *x);
unsigned int comedi_buf_write_n_available(struct comedi_async *async);
unsigned int comedi_buf_write_alloc(struct comedi_async *async,
unsigned int nbytes);
unsigned int comedi_buf_write_alloc_strict(struct comedi_async *async,