can: peak_usb: pcan_usb_encode_msg(): add information

This patch adds information by replacing a hard-coded values with its
symbol and a adding comment.

Link: https://lore.kernel.org/r/20210625130931.27438-5-s.grosjean@peak-system.com
Signed-off-by: Stephane Grosjean <s.grosjean@peak-system.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/usb/peak_usb/pcan_usb.c b/drivers/net/can/usb/peak_usb/pcan_usb.c
index 2362ac8..fea44e3 100644 (file)
--- a/drivers/net/can/usb/peak_usb/pcan_usb.c
+++ b/drivers/net/can/usb/peak_usb/pcan_usb.c
@@ -63,6 +63,8 @@
 
 #define PCAN_USB_MSG_HEADER_LEN                2
 
+#define PCAN_USB_MSG_TX_CAN            2       /* Tx msg is a CAN frame */
+
 /* PCAN-USB adapter internal clock (MHz) */
 #define PCAN_USB_CRYSTAL_HZ            16000000
 
@@ -834,8 +836,8 @@ static int pcan_usb_encode_msg(struct peak_usb_device *dev, struct sk_buff *skb,
        u32 can_id_flags = cf->can_id & CAN_ERR_MASK;
        u8 *pc;
 
-       obuf[0] = 2;
-       obuf[1] = 1;
+       obuf[0] = PCAN_USB_MSG_TX_CAN;
+       obuf[1] = 1;    /* only one CAN frame is stored in the packet */
 
        pc = obuf + PCAN_USB_MSG_HEADER_LEN;