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staging: comedi: add new comedi_buf_write_n_available()

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Add a new function `comedi_buf_write_n_available()` to return the amount
of buffer space available for writing, including space already allocated
by `comedi_buf_write_alloc()` plus any unallocated space available.
This is currently just for internal use by the comedi core, so is not
exported.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ian Abbott 2015-10-09 12:26:49 +01:00 committed by Greg Kroah-Hartman
parent 274ec5ee54
commit 432fbde739
2 changed files with 9 additions and 0 deletions
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8
drivers/staging/comedi/comedi_buf.c
View File

@ -253,6 +253,14 @@ static unsigned int comedi_buf_write_n_unalloc(struct comedi_subdevice *s)
return free_end - async->buf_write_alloc_count;
}
unsigned int comedi_buf_write_n_available(struct comedi_subdevice *s)
{
struct comedi_async *async = s->async;
unsigned int free_end = async->buf_read_count + async->prealloc_bufsz;
return free_end - async->buf_write_count;
}
/**
* comedi_buf_write_alloc() - Reserve buffer space for writing
* @s: COMEDI subdevice.

1
drivers/staging/comedi/comedi_internal.h
View File

@ -31,6 +31,7 @@ void comedi_buf_map_get(struct comedi_buf_map *bm);
int comedi_buf_map_put(struct comedi_buf_map *bm);
struct comedi_buf_map *comedi_buf_map_from_subdev_get(
struct comedi_subdevice *s);
unsigned int comedi_buf_write_n_available(struct comedi_subdevice *s);
unsigned int comedi_buf_write_n_allocated(struct comedi_subdevice *s);
void comedi_device_cancel_all(struct comedi_device *dev);
bool comedi_can_auto_free_spriv(struct comedi_subdevice *s);