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author | H Hartley Sweeten <hsweeten@visionengravers.com> | 2013-01-09 20:27:48 (GMT) |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2013-01-18 00:53:58 (GMT) |
commit | f8f76e909b8cc6696071e69cf4be07714c95bcb4 (patch) | |
tree | 92c1c24246f38177ce10f80f998ac07d933c18b2 /drivers/staging/comedi/comedi_buf.c | |
parent | 61c9fb0eb08bc9b7164a6181b0062d9959406a34 (diff) | |
download | linux-f8f76e909b8cc6696071e69cf4be07714c95bcb4.tar.xz |
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: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/staging/comedi/comedi_buf.c')
-rw-r--r-- | drivers/staging/comedi/comedi_buf.c | 52 |
1 files changed, 21 insertions, 31 deletions
diff --git a/drivers/staging/comedi/comedi_buf.c b/drivers/staging/comedi/comedi_buf.c index 9392453..2f38a87 100644 --- a/drivers/staging/comedi/comedi_buf.c +++ b/drivers/staging/comedi/comedi_buf.c @@ -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 |