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Commit f8f76e90 authored by H Hartley Sweeten's avatar H Hartley Sweeten Committed by Greg Kroah-Hartman
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staging: comedi: comedi_buf: factor out common comedi_buf_write_alloc_* code 



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: default avatarH Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: default avatarIan Abbott <abbotti@mev.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 61c9fb0e

drivers/staging/comedi/comedi_buf.c

+21 −31
Original line number Diff line number Diff line
@@ -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

drivers/staging/comedi/comedidev.h

+0 −1
Original line number Diff line number Diff line
@@ -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,