diff options
Diffstat (limited to 'drivers/staging/comedi/comedi_buf.c')
| -rw-r--r-- | drivers/staging/comedi/comedi_buf.c | 125 |
1 files changed, 101 insertions, 24 deletions
diff --git a/drivers/staging/comedi/comedi_buf.c b/drivers/staging/comedi/comedi_buf.c index 19e7b229d15e..90c28016c6c1 100644 --- a/drivers/staging/comedi/comedi_buf.c +++ b/drivers/staging/comedi/comedi_buf.c @@ -245,7 +245,7 @@ void comedi_buf_reset(struct comedi_subdevice *s) async->events = 0; } -static unsigned int comedi_buf_write_n_available(struct comedi_subdevice *s) +static unsigned int comedi_buf_write_n_unalloc(struct comedi_subdevice *s) { struct comedi_async *async = s->async; unsigned int free_end = async->buf_read_count + async->prealloc_bufsz; @@ -253,15 +253,33 @@ 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 */ +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. + * @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) { struct comedi_async *async = s->async; - unsigned int available = comedi_buf_write_n_available(s); + unsigned int unalloc = comedi_buf_write_n_unalloc(s); - if (nbytes > available) - nbytes = available; + if (nbytes > unalloc) + nbytes = unalloc; async->buf_write_alloc_count += nbytes; @@ -329,7 +347,21 @@ 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 +381,17 @@ 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 +412,21 @@ 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 +454,19 @@ 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) { @@ -469,15 +538,21 @@ static void comedi_buf_memcpy_from(struct comedi_subdevice *s, } /** - * comedi_buf_write_samples - write sample data to comedi buffer - * @s: comedi_subdevice struct - * @data: samples - * @nsamples: number of samples + * comedi_buf_write_samples() - Write sample data to COMEDI buffer + * @s: COMEDI subdevice. + * @data: Pointer to source samples. + * @nsamples: Number of samples to write. * - * Writes nsamples to the comedi buffer associated with the subdevice, marks - * it as written and updates the acquisition scan progress. + * Write up to @nsamples samples to the COMEDI acquisition data buffer + * associated with the subdevice, mark it as written and update the + * acquisition scan progress. If there is not enough room for the specified + * number of samples, the number of samples written is limited to the number + * that will fit and the %COMEDI_CB_OVERFLOW event flag is set to cause the + * acquisition to terminate with an overrun error. Set the %COMEDI_CB_BLOCK + * event flag if any samples are written to cause waiting tasks to be woken + * when the event flags are processed. * - * Returns the amount of data written in bytes. + * Return: The amount of data written in bytes. */ unsigned int comedi_buf_write_samples(struct comedi_subdevice *s, const void *data, unsigned int nsamples) @@ -490,8 +565,7 @@ unsigned int comedi_buf_write_samples(struct comedi_subdevice *s, * If not, clamp the nsamples to the number that will fit, flag the * buffer overrun and add the samples that fit. */ - max_samples = comedi_bytes_to_samples(s, - comedi_buf_write_n_available(s)); + max_samples = comedi_bytes_to_samples(s, comedi_buf_write_n_unalloc(s)); if (nsamples > max_samples) { dev_warn(s->device->class_dev, "buffer overrun\n"); s->async->events |= COMEDI_CB_OVERFLOW; @@ -513,15 +587,18 @@ unsigned int comedi_buf_write_samples(struct comedi_subdevice *s, EXPORT_SYMBOL_GPL(comedi_buf_write_samples); /** - * comedi_buf_read_samples - read sample data from comedi buffer - * @s: comedi_subdevice struct - * @data: destination - * @nsamples: maximum number of samples to read + * comedi_buf_read_samples() - Read sample data from COMEDI buffer + * @s: COMEDI subdevice. + * @data: Pointer to destination. + * @nsamples: Maximum number of samples to read. * - * Reads up to nsamples from the comedi buffer associated with the subdevice, - * marks it as read and updates the acquisition scan progress. + * Read up to @nsamples samples from the COMEDI acquisition data buffer + * associated with the subdevice, mark it as read and update the acquisition + * scan progress. Limit the number of samples read to the number available. + * Set the %COMEDI_CB_BLOCK event flag if any samples are read to cause waiting + * tasks to be woken when the event flags are processed. * - * Returns the amount of data read in bytes. + * Return: The amount of data read in bytes. */ unsigned int comedi_buf_read_samples(struct comedi_subdevice *s, void *data, unsigned int nsamples) |