On 20/10/14 19:52, H Hartley Sweeten wrote:
Introduce a generic method to read samples from the async buffer.
The size of each sample is detected automatically using the bytes_per_sample()
helper. The unsigned long long is used to avoid any possible integer overflow
when calculating the 'nbytes' for all the requested samples. This value is
then clampled to the actual size of the async buffer. The samples are read
from the async buffer using comedi_read_array_from_buffer().
This will allow converting all the comedi drivers to use a common method when
reading data from the async buffer.
Since comedi_read_array_from_buffer() sets the COMEDI_CB_BLOCK event after
reading the data, those events can be removed from the drivers.
In addition, comedi_inc_scan_progress() will automatically detect the end of
scan and set the COMEDI_CB_EOS event. Those events can also be removed from
the drivers.
Signed-off-by: H Hartley Sweeten <hsweeten@xxxxxxxxxxxxxxxxxxx>
Cc: Ian Abbott <abbotti@xxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/staging/comedi/comedi_buf.c | 23 +++++++++++++++++++++++
drivers/staging/comedi/comedidev.h | 2 ++
2 files changed, 25 insertions(+)
diff --git a/drivers/staging/comedi/comedi_buf.c b/drivers/staging/comedi/comedi_buf.c
index c60a45ad..03b475a 100644
--- a/drivers/staging/comedi/comedi_buf.c
+++ b/drivers/staging/comedi/comedi_buf.c
@@ -575,3 +575,26 @@ unsigned int comedi_read_array_from_buffer(struct comedi_subdevice *s,
return num_bytes;
}
EXPORT_SYMBOL_GPL(comedi_read_array_from_buffer);
+
+/**
+ * comedi_buf_read_samples - read sample data from comedi buffer
+ * @s: comedi_subdevice struct
+ * @data: 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.
+ *
+ * Returns the amount of data read in bytes.
+ */
+unsigned int comedi_buf_read_samples(struct comedi_subdevice *s,
+ void *data, unsigned int nsamples)
+{
+ unsigned long long nbytes = nsamples * bytes_per_sample(s);
That doesn't do what you think. One of the operands of '*' would have
to be cast to '(unsigned long long)' first.
The other option is to clamp 'nsamples' to 's->async->prealloc_bufsz /
bytes_per_sample(s)'. If there was a log2 version of
bytes_per_sample(), the division could be replaced with a bit-shift (the
compiler probably isn't clever enough to do that optimization by
itself). On a side-note, 'bytes_per_sample()' ought to be renamed to
'comedi_bytes_per_sample()' at some point.
+
+ if (nbytes > s->async->prealloc_bufsz)
+ nbytes = s->async->prealloc_bufsz;
+
+ return comedi_read_array_from_buffer(s, data, nbytes);
+}
+EXPORT_SYMBOL_GPL(comedi_buf_read_samples);
diff --git a/drivers/staging/comedi/comedidev.h b/drivers/staging/comedi/comedidev.h
index fb8ff84..ba4084b 100644
--- a/drivers/staging/comedi/comedidev.h
+++ b/drivers/staging/comedi/comedidev.h
@@ -453,6 +453,8 @@ unsigned int comedi_write_array_to_buffer(struct comedi_subdevice *s,
unsigned int num_bytes);
unsigned int comedi_read_array_from_buffer(struct comedi_subdevice *s,
void *data, unsigned int num_bytes);
+unsigned int comedi_buf_read_samples(struct comedi_subdevice *s,
+ void *data, unsigned int nsamples);
/* drivers.c - general comedi driver functions */
--
-=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@xxxxxxxxx> )=-
-=( Web: http://www.mev.co.uk/ )=-
_______________________________________________
devel mailing list
devel@xxxxxxxxxxxxxxxxxxxxxx
http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
