tools: iio: convert iio_generic_buffer to use new IIO buffer API

This change makes use of the new IIO buffer API to read data from an IIO
buffer.
It doesn't read the /sys/bus/iio/devices/iio:deviceX/scan_elements dir
anymore, it reads /sys/bus/iio/devices/iio:deviceX/bufferY, where all the
scan_elements have been merged together with the old/classical buffer
attributes.

And it makes use of the new IIO_BUFFER_GET_FD_IOCTL ioctl to get an FD for
the IIO buffer for which to read data from.
It also does a quick sanity check to see that -EBUSY is returned if reading
the chardev after the ioctl() has succeeded.

This was tested with the following cases:
 1. Tested buffer0 works with ioctl()
 2. Tested that buffer0 can't be opened via /dev/iio:deviceX after ioctl()
    This check should be omitted under normal operation; it's being done
    here to check that the driver change is sane
 3. Moved valid buffer0 to be buffer1, and tested that data comes from it

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20210215104043.91251-25-alexandru.ardelean@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

1 files changed, 8 insertions, 5 deletions

diff --git a/tools/iio/iio_utils.c b/tools/iio/iio_utils.c
index a96002f2c2d5..aadee6d34c74 100644
--- a/tools/iio/iio_utils.c
+++ b/tools/iio/iio_utils.c
@@ -77,6 +77,7 @@ int iioutils_break_up_name(const char *full_name, char **generic_name)
  * @mask: output a bit mask for the raw data
  * @be: output if data in big endian
  * @device_dir: the IIO device directory
+ * @buffer_idx: the IIO buffer index
  * @name: the channel name
  * @generic_name: the channel type name
  *
@@ -85,8 +86,8 @@ int iioutils_break_up_name(const char *full_name, char **generic_name)
 static int iioutils_get_type(unsigned int *is_signed, unsigned int *bytes,
 			     unsigned int *bits_used, unsigned int *shift,
 			     uint64_t *mask, unsigned int *be,
-			     const char *device_dir, const char *name,
-			     const char *generic_name)
+			     const char *device_dir, int buffer_idx,
+			     const char *name, const char *generic_name)
 {
 	FILE *sysfsfp;
 	int ret;
@@ -96,7 +97,7 @@ static int iioutils_get_type(unsigned int *is_signed, unsigned int *bytes,
 	unsigned padint;
 	const struct dirent *ent;
 
-	ret = asprintf(&scan_el_dir, FORMAT_SCAN_ELEMENTS_DIR, device_dir);
+	ret = asprintf(&scan_el_dir, FORMAT_SCAN_ELEMENTS_DIR, device_dir, buffer_idx);
 	if (ret < 0)
 		return -ENOMEM;
 
@@ -304,12 +305,13 @@ void bsort_channel_array_by_index(struct iio_channel_info *ci_array, int cnt)
 /**
  * build_channel_array() - function to figure out what channels are present
  * @device_dir: the IIO device directory in sysfs
+ * @buffer_idx: the IIO buffer for this channel array
  * @ci_array: output the resulting array of iio_channel_info
  * @counter: output the amount of array elements
  *
  * Returns 0 on success, otherwise a negative error code.
  **/
-int build_channel_array(const char *device_dir,
+int build_channel_array(const char *device_dir, int buffer_idx,
 			struct iio_channel_info **ci_array, int *counter)
 {
 	DIR *dp;
@@ -322,7 +324,7 @@ int build_channel_array(const char *device_dir,
 	char *filename;
 
 	*counter = 0;
-	ret = asprintf(&scan_el_dir, FORMAT_SCAN_ELEMENTS_DIR, device_dir);
+	ret = asprintf(&scan_el_dir, FORMAT_SCAN_ELEMENTS_DIR, device_dir, buffer_idx);
 	if (ret < 0)
 		return -ENOMEM;
 
@@ -503,6 +505,7 @@ int build_channel_array(const char *device_dir,
 						&current->mask,
 						&current->be,
 						device_dir,
+						buffer_idx,
 						current->name,
 						current->generic_name);
 			if (ret < 0)