iio: buffer: Expose data available

Add a sysfs attribute that exposes buffer data available to userspace.
This attribute can be checked at runtime to determine the overall buffer
fill level (across all allocated buffers).

Signed-off-by: Matt Fornero <matt.fornero@mathworks.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
index a478740..9cc0ea1 100644 (file)
--- a/Documentation/ABI/testing/sysfs-bus-iio
+++ b/Documentation/ABI/testing/sysfs-bus-iio
@@ -1413,6 +1413,16 @@ Description:
                the available samples after the timeout expires and thus have a
                maximum delay guarantee.
 
+What:          /sys/bus/iio/devices/iio:deviceX/buffer/data_available
+KernelVersion: 4.16
+Contact:       linux-iio@vger.kernel.org
+Description:
+               A read-only value indicating the bytes of data available in the
+               buffer. In the case of an output buffer, this indicates the
+               amount of empty space available to write data to. In the case of
+               an input buffer, this indicates the amount of data available for
+               reading.
+
 What:          /sys/bus/iio/devices/iio:deviceX/buffer/hwfifo_enabled
 KernelVersion: 4.2
 Contact:       linux-iio@vger.kernel.org

diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
index d2b4651..eda2a0f 100644 (file)
--- a/drivers/iio/industrialio-buffer.c
+++ b/drivers/iio/industrialio-buffer.c
@@ -1198,6 +1198,18 @@ out:
        return ret ? ret : len;
 }
 
+static ssize_t iio_dma_show_data_available(struct device *dev,
+                                               struct device_attribute *attr,
+                                               char *buf)
+{
+       struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+       size_t bytes;
+
+       bytes = iio_buffer_data_available(indio_dev->buffer);
+
+       return sprintf(buf, "%zu\n", bytes);
+}
+
 static DEVICE_ATTR(length, S_IRUGO | S_IWUSR, iio_buffer_read_length,
                   iio_buffer_write_length);
 static struct device_attribute dev_attr_length_ro = __ATTR(length,
@@ -1208,11 +1220,14 @@ static DEVICE_ATTR(watermark, S_IRUGO | S_IWUSR,
                   iio_buffer_show_watermark, iio_buffer_store_watermark);
 static struct device_attribute dev_attr_watermark_ro = __ATTR(watermark,
        S_IRUGO, iio_buffer_show_watermark, NULL);
+static DEVICE_ATTR(data_available, S_IRUGO,
+               iio_dma_show_data_available, NULL);
 
 static struct attribute *iio_buffer_attrs[] = {
        &dev_attr_length.attr,
        &dev_attr_enable.attr,
        &dev_attr_watermark.attr,
+       &dev_attr_data_available.attr,
 };
 
 int iio_buffer_alloc_sysfs_and_mask(struct iio_dev *indio_dev)