staging: wfx: explain the purpose of wfx_send_pds()

On first look, the goal of wfx_send_pds() is not obvious. A small
explanation is welcomed.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20210913130203.1903622-31-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wfx/main.c

@@ -163,7 +163,20 @@ bool wfx_api_older_than(struct wfx_dev *wdev, int major, int minor)
 	return false;
 }
 
-/* NOTE: wfx_send_pds() destroy buf */
+/* The device needs data about the antenna configuration. This information in
+ * provided by PDS (Platform Data Set, this is the wording used in WF200
+ * documentation) files. For hardware integrators, the full process to create
+ * PDS files is described here:
+ *   https:github.com/SiliconLabs/wfx-firmware/blob/master/PDS/README.md
+ *
+ * So this function aims to send PDS to the device. However, the PDS file is
+ * often bigger than Rx buffers of the chip, so it has to be sent in multiple
+ * parts.
+ *
+ * In add, the PDS data cannot be split anywhere. The PDS files contains tree
+ * structures. Braces are used to enter/leave a level of the tree (in a JSON
+ * fashion). PDS files can only been split between root nodes.
+ */
 int wfx_send_pds(struct wfx_dev *wdev, u8 *buf, size_t len)
 {
 	int ret;