This patch changes the semantics of non-blocking reads so that a hardware fifo flush is triggered if the available data in the device buffer is less then the requested size.
This allows userspace to accurately generate hardware fifo flushes, by doing a non-blocking read with a size greater then the sum of the device buffer and hardware fifo size. Signed-off-by: Octavian Purdila <[email protected]> --- This is the second iteration of the patch that allows userspace to accurately generate flush events. The first RFC patch set was discussed here: https://lkml.org/lkml/2015/4/29/202 drivers/iio/industrialio-buffer.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c index df919f4..24085db 100644 --- a/drivers/iio/industrialio-buffer.c +++ b/drivers/iio/industrialio-buffer.c @@ -71,8 +71,9 @@ static bool iio_buffer_ready(struct iio_dev *indio_dev, struct iio_buffer *buf, if (avail >= to_wait) { /* force a flush for non-blocking reads */ - if (!to_wait && !avail && to_flush) - iio_buffer_flush_hwfifo(indio_dev, buf, to_flush); + if (!to_wait && avail < to_flush) + iio_buffer_flush_hwfifo(indio_dev, buf, + to_flush - avail); return true; } @@ -100,8 +101,7 @@ ssize_t iio_buffer_read_first_n_outer(struct file *filp, char __user *buf, struct iio_dev *indio_dev = filp->private_data; struct iio_buffer *rb = indio_dev->buffer; size_t datum_size; - size_t to_wait = 0; - size_t to_read; + size_t to_wait; int ret; if (!indio_dev->info) @@ -119,14 +119,14 @@ ssize_t iio_buffer_read_first_n_outer(struct file *filp, char __user *buf, if (!datum_size) return 0; - to_read = min_t(size_t, n / datum_size, rb->watermark); - - if (!(filp->f_flags & O_NONBLOCK)) - to_wait = to_read; + if (filp->f_flags & O_NONBLOCK) + to_wait = 0; + else + to_wait = min_t(size_t, n / datum_size, rb->watermark); do { ret = wait_event_interruptible(rb->pollq, - iio_buffer_ready(indio_dev, rb, to_wait, to_read)); + iio_buffer_ready(indio_dev, rb, to_wait, n / datum_size)); if (ret) return ret; -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
