From 8d4be669479d95a0c6eb4b6a538460f0ab35c4f7 Mon Sep 17 00:00:00 2001 From: H Hartley Sweeten Date: Wed, 9 Jan 2013 13:29:19 -0700 Subject: [PATCH] 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: H Hartley Sweeten Signed-off-by: Ian Abbott Signed-off-by: Greg Kroah-Hartman --- drivers/staging/comedi/comedi_buf.c | 74 ++++++++++++++++------------- 1 file changed, 41 insertions(+), 33 deletions(-) diff --git a/drivers/staging/comedi/comedi_buf.c b/drivers/staging/comedi/comedi_buf.c index 1b269a7a07ac..95cbe365ded2 100644 --- a/drivers/staging/comedi/comedi_buf.c +++ b/drivers/staging/comedi/comedi_buf.c @@ -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) { @@ -203,40 +205,46 @@ 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; - } - /* don't munge partial samples */ - num_bytes -= num_bytes % num_sample_bytes; - while (count < num_bytes) { - int block_size; - - 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; + count = num_bytes; + } else { + /* don't munge partial samples */ + num_bytes -= num_bytes % num_sample_bytes; + while (count < num_bytes) { + int block_size = num_bytes - count; + unsigned int buf_end; + + if (block_size < 0) { + dev_warn(s->device->class_dev, + "%s: %s: bug! block_size is negative\n", + __FILE__, __func__); + break; + } + + 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); + + /* + * 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; + async->munge_count += block_size; + async->munge_ptr += block_size; + async->munge_ptr %= async->prealloc_bufsz; + count += block_size; } - 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, - block_size, async->munge_chan); - - smp_wmb(); /* barrier insures data is munged in buffer - * before munge_count is incremented */ - - async->munge_chan += block_size / num_sample_bytes; - async->munge_chan %= async->cmd.chanlist_len; - async->munge_count += block_size; - async->munge_ptr += block_size; - async->munge_ptr %= async->prealloc_bufsz; - count += block_size; } + BUG_ON((int)(async->munge_count - async->buf_write_count) > 0); return count; } -- 2.30.2