[PATCH v2] staging: pi433: add docs to packet_format and tx_start_condition enum

[Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@gmail.com>]

While pi433 driver deals with the nuances of the different possible
config combinations, it's hard (at first) to understand the rationale
for some of the tx/rx-related source code unless you're fairly familiar
with the rf69's inner workings.

This patch documents the expected behaviour and limits of both
packet_format and tx_start_condition enum fields.

Signed-off-by: Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@gmail.com>
---
v2: removed comments pointed out during v1 review (Req Greg k-h)
v1: https://lore.kernel.org/lkml/20211229094713.GA28795@localhost.localdomain/
---
 drivers/staging/pi433/rf69_enum.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/staging/pi433/rf69_enum.h b/drivers/staging/pi433/rf69_enum.h
index fbf56fcf5fe8..0f0fa741d089 100644
--- a/drivers/staging/pi433/rf69_enum.h
+++ b/drivers/staging/pi433/rf69_enum.h
@@ -110,12 +110,24 @@ enum fifo_fill_condition {
 };
 
 enum packet_format {
+    /*
+     * Used when the size of payload is fixed in advance. This mode of
+     * operation may be of interest to minimize RF overhead by 1 byte as
+     * no length byte field is required
+     */
 	packet_length_fix,
+    /*
+     * Used when the size of payload isn't known in advance. It requires the
+     * transmitter to send the length byte in each packet so the receiver
+     * would know how to operate properly
+     */
 	packet_length_var
 };
 
 enum tx_start_condition {
+    /* the number of bytes in the FIFO exceeds FIFO_THRESHOLD */
 	fifo_level,
+    /* at least one byte in the FIFO */
 	fifo_not_empty
 };
 
-- 
2.25.4