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Commit 8d4be669 authored by H Hartley Sweeten's avatar H Hartley Sweeten Committed by Greg Kroah-Hartman
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staging: comedi: comedi_buf: cleanup comedi_buf_munge() 



Refactor this function so there is a single return point and only
one BUG_ON check. The BUG_ON needs to be looked at to see if it
can be safely removed.

Clarify the test in the munge loop that checks for a block copy
that would extend pass the end of the prealloc_buf.

Reword the comment about the need for the smp_wmb().

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 47181eab

drivers/staging/comedi/comedi_buf.c

+41 −33
Original line number Diff line number Diff line
@@ -194,8 +194,10 @@ unsigned int comedi_buf_write_alloc(struct comedi_async *async, 
}

EXPORT_SYMBOL(comedi_buf_write_alloc);



/* munging is applied to data by core as it passes between user

 * and kernel space */

/*

 * munging is applied to data by core as it passes between user

 * and kernel space

 */

static unsigned int comedi_buf_munge(struct comedi_async *async,

				     unsigned int num_bytes)

{
@@ -203,32 +205,36 @@ static unsigned int comedi_buf_munge(struct comedi_async *async, 
	unsigned int count = 0;

	const unsigned num_sample_bytes = bytes_per_sample(s);



	if (s->munge == NULL || (async->cmd.flags & CMDF_RAWDATA)) {

	if (!s->munge || (async->cmd.flags & CMDF_RAWDATA)) {

		async->munge_count += num_bytes;

		BUG_ON((int)(async->munge_count - async->buf_write_count) > 0);

		return num_bytes;

	}

		count = num_bytes;

	} else {

		/* don't munge partial samples */

		num_bytes -= num_bytes % num_sample_bytes;

		while (count < num_bytes) {

		int block_size;

			int block_size = num_bytes - count;

			unsigned int buf_end;



		block_size = num_bytes - count;

			if (block_size < 0) {

				dev_warn(s->device->class_dev,

					"%s: %s: bug! block_size is negative\n",

					__FILE__, __func__);

				break;

			}

		if ((int)(async->munge_ptr + block_size -

			  async->prealloc_bufsz) > 0)

			block_size = async->prealloc_bufsz - async->munge_ptr;



		s->munge(s->device, s, async->prealloc_buf + async->munge_ptr,

			buf_end = async->prealloc_bufsz - async->munge_ptr;

			if (block_size > buf_end)

				block_size = buf_end;



			s->munge(s->device, s,

				 async->prealloc_buf + async->munge_ptr,

				 block_size, async->munge_chan);



		smp_wmb();	/* barrier insures data is munged in buffer

				 * before munge_count is incremented */

			/*

			 * ensure data is munged in buffer before the

			 * async buffer munge_count is incremented

			 */

			smp_wmb();



			async->munge_chan += block_size / num_sample_bytes;

			async->munge_chan %= async->cmd.chanlist_len;
@@ -237,6 +243,8 @@ static unsigned int comedi_buf_munge(struct comedi_async *async, 
			async->munge_ptr %= async->prealloc_bufsz;

			count += block_size;

		}

	}



	BUG_ON((int)(async->munge_count - async->buf_write_count) > 0);

	return count;

}