staging: most: hdm-usb: add comment

This patch adds a comment to function hdm_configure_channel() to clarify
its execution paths.

Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/most/hdm-usb/hdm_usb.c b/drivers/staging/most/hdm-usb/hdm_usb.c
index 3433646..d6db0bd 100644 (file)
--- a/drivers/staging/most/hdm-usb/hdm_usb.c
+++ b/drivers/staging/most/hdm-usb/hdm_usb.c
@@ -634,6 +634,15 @@ _error:
  * @iface: interface
  * @channel: channel ID
  * @conf: structure that holds the configuration information
+ *
+ * The attached network interface controller (NIC) supports a padding mode
+ * to avoid short packets on USB, hence increasing the performance due to a
+ * lower interrupt load. This mode is default for synchronous data and can
+ * be switched on for isochronous data. In case padding is active the
+ * driver needs to know the frame size of the payload in order to calculate
+ * the number of bytes it needs to pad when transmitting or to cut off when
+ * receiving data.
+ *
  */
 static int hdm_configure_channel(struct most_interface *iface, int channel,
                                 struct most_channel_config *conf)
@@ -667,6 +676,11 @@ static int hdm_configure_channel(struct most_interface *iface, int channel,
            !(conf->data_type == MOST_CH_ISOC &&
              conf->packets_per_xact != 0xFF)) {
                mdev->padding_active[channel] = false;
+               /*
+                * Since the NIC's padding mode is not going to be
+                * used, we can skip the frame size calculations and
+                * move directly on to exit.
+                */
                goto exit;
        }