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@xxxxxxxxxxxxxxxxxxx>
Cc: Ian Abbott <abbobbi@xxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/staging/comedi/comedi_buf.c | 52 +++++++++++++++----------------------
drivers/staging/comedi/comedidev.h | 1 -
2 files changed, 21 insertions(+), 32 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
diff --git a/drivers/staging/comedi/comedidev.h b/drivers/staging/comedi/comedidev.h
index c3bc4b7..bf0fd8d 100644
--- a/drivers/staging/comedi/comedidev.h
+++ b/drivers/staging/comedi/comedidev.h
@@ -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,
--
1.8.0
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