diff options
| -rw-r--r-- | drivers/staging/comedi/comedi_buf.c | 69 |
1 files changed, 65 insertions, 4 deletions
diff --git a/drivers/staging/comedi/comedi_buf.c b/drivers/staging/comedi/comedi_buf.c index 63553d9dc051..d45a4b65e8d3 100644 --- a/drivers/staging/comedi/comedi_buf.c +++ b/drivers/staging/comedi/comedi_buf.c @@ -253,7 +253,17 @@ static unsigned int comedi_buf_write_n_available(struct comedi_subdevice *s) return free_end - async->buf_write_alloc_count; } -/* allocates chunk for the writer from free buffer space */ +/** + * comedi_buf_write_alloc() - Reserve buffer space for writing + * @s: COMEDI subdevice. + * @nbytes: Maximum space to reserve in bytes. + * + * Reserve up to @nbytes bytes of space to be written in the COMEDI acquisition + * data buffer associated with the subdevice. The amount reserved is limited + * by the space available. + * + * Return: The amount of space reserved in bytes. + */ unsigned int comedi_buf_write_alloc(struct comedi_subdevice *s, unsigned int nbytes) { @@ -329,7 +339,21 @@ unsigned int comedi_buf_write_n_allocated(struct comedi_subdevice *s) return async->buf_write_alloc_count - async->buf_write_count; } -/* transfers a chunk from writer to filled buffer space */ +/** + * comedi_buf_write_free() - Free buffer space after it is written + * @s: COMEDI subdevice. + * @nbytes: Maximum space to free in bytes. + * + * Free up to @nbytes bytes of space previously reserved for writing in the + * COMEDI acquisition data buffer associated with the subdevice. The amount of + * space freed is limited to the amount that was reserved. The freed space is + * assumed to have been filled with sample data by the writer. + * + * If the samples in the freed space need to be "munged", do so here. The + * freed space becomes available for allocation by the reader. + * + * Return: The amount of space freed in bytes. + */ unsigned int comedi_buf_write_free(struct comedi_subdevice *s, unsigned int nbytes) { @@ -349,6 +373,17 @@ unsigned int comedi_buf_write_free(struct comedi_subdevice *s, } EXPORT_SYMBOL_GPL(comedi_buf_write_free); +/** + * comedi_buf_read_n_available() - Determine amount of readable buffer space + * @s: COMEDI subdevice. + * + * Determine the amount of readable buffer space in the COMEDI acquisition data + * buffer associated with the subdevice. The readable buffer space is that + * which has been freed by the writer and "munged" to the sample data format + * expected by COMEDI if necessary. + * + * Return: The amount of readable buffer space. + */ unsigned int comedi_buf_read_n_available(struct comedi_subdevice *s) { struct comedi_async *async = s->async; @@ -369,7 +404,21 @@ unsigned int comedi_buf_read_n_available(struct comedi_subdevice *s) } EXPORT_SYMBOL_GPL(comedi_buf_read_n_available); -/* allocates a chunk for the reader from filled (and munged) buffer space */ +/** + * comedi_buf_read_alloc() - Reserve buffer space for reading + * @s: COMEDI subdevice. + * @nbytes: Maximum space to reserve in bytes. + * + * Reserve up to @nbytes bytes of previously written and "munged" buffer space + * for reading in the COMEDI acquisition data buffer associated with the + * subdevice. The amount reserved is limited to the space available. The + * reader can read from the reserved space and then free it. A reader is also + * allowed to read from the space before reserving it as long as it determines + * the amount of readable data available, but the space needs to be marked as + * reserved before it can be freed. + * + * Return: The amount of space reserved in bytes. + */ unsigned int comedi_buf_read_alloc(struct comedi_subdevice *s, unsigned int nbytes) { @@ -397,7 +446,19 @@ static unsigned int comedi_buf_read_n_allocated(struct comedi_async *async) return async->buf_read_alloc_count - async->buf_read_count; } -/* transfers control of a chunk from reader to free buffer space */ +/** + * comedi_buf_read_free() - Free buffer space after it has been read + * @s: COMEDI subdevice. + * @nbytes: Maximum space to free in bytes. + * + * Free up to @nbytes bytes of buffer space previously reserved for reading in + * the COMEDI acquisition data buffer associated with the subdevice. The + * amount of space freed is limited to the amount that was reserved. + * + * The freed space becomes available for allocation by the writer. + * + * Return: The amount of space freed in bytes. + */ unsigned int comedi_buf_read_free(struct comedi_subdevice *s, unsigned int nbytes) { |