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iio: add watermark logic to iio read and poll

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Currently the IIO buffer blocking read only wait until at least one
data element is available.
This patch makes the reader sleep until enough data is collected before
returning to userspace. This should limit the read() calls count when
trying to get data in batches.

Co-author: Yannick Bedhomme <yannick.bedhomme@mobile-devices.fr>
Signed-off-by: Josselin Costanzi <josselin.costanzi@mobile-devices.fr>
[rebased and remove buffer timeout]
Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Josselin Costanzi
2015-03-22 20:33:38 +02:00
committed by Jonathan Cameron
parent 9444a300c2
commit 37d3455672
5 changed files with 132 additions and 28 deletions
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8
include/linux/iio/buffer.h
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@@ -21,8 +21,8 @@ struct iio_buffer;
* struct iio_buffer_access_funcs - access functions for buffers.
* @store_to: actually store stuff to the buffer
* @read_first_n: try to get a specified number of bytes (must exist)
* @data_available: indicates whether data for reading from the buffer is
* available.
* @data_available: indicates how much data is available for reading from
* the buffer.
* @request_update: if a parameter change has been marked, update underlying
* storage.
* @set_bytes_per_datum:set number of bytes per datum
@@ -43,7 +43,7 @@ struct iio_buffer_access_funcs {
int (*read_first_n)(struct iio_buffer *buffer,
size_t n,
char __user *buf);
bool (*data_available)(struct iio_buffer *buffer);
size_t (*data_available)(struct iio_buffer *buffer);
int (*request_update)(struct iio_buffer *buffer);
@@ -72,6 +72,7 @@ struct iio_buffer_access_funcs {
* @demux_bounce: [INTERN] buffer for doing gather from incoming scan.
* @buffer_list: [INTERN] entry in the devices list of current buffers.
* @ref: [INTERN] reference count of the buffer.
* @watermark: [INTERN] number of datums to wait for poll/read.
*/
struct iio_buffer {
int length;
@@ -90,6 +91,7 @@ struct iio_buffer {
void *demux_bounce;
struct list_head buffer_list;
struct kref ref;
unsigned int watermark;
};
/**