can: esd_usb: Make use of existing kernel macros

Make use of existing kernel macros:
- Use the unit suffixes from linux/units.h for the controller clock
frequencies
- Use the BIT() and the GENMASK() macro to set specific bits in some
  constants
- Use CAN_MAX_DLEN (instead of directly using the value 8) for the
maximum CAN payload length

Additionally:
- Spend some commenting for the previously changed constants
- Add the current year to the copyright notice
- While adding the header linux/units.h to the list of include files
also sort that list alphabetically
Suggested-by: Vincent MAILHOL <mailhol.vincent@wanadoo.fr>
Link: https://lore.kernel.org/all/CAMZ6RqLaDNy-fZ2G0+QMhUEckkXLL+ZyELVSDFmqpd++aBzZQg@mail.gmail.com/
Link: https://lore.kernel.org/all/CAMZ6RqKdg5YBufa0C+ttzJvoG=9yuti-8AmthCi4jBbd08JEtw@mail.gmail.com/Suggested-by: Marc Kleine-Budde <mkl@pengutronix.de>
Link: https://lore.kernel.org/all/20230518-grower-film-ea8b5f853f3e-mkl@pengutronix.de/Signed-off-by: Frank Jungclaus <frank.jungclaus@esd.eu>
Link: https://lore.kernel.org/r/20230519195600.420644-2-frank.jungclaus@esd.eu
[mkl: remove hex constants in comments after BIT()]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/usb/esd_usb.c

@@ -3,18 +3,19 @@
  * CAN driver for esd electronics gmbh CAN-USB/2 and CAN-USB/Micro
  *
  * Copyright (C) 2010-2012 esd electronic system design gmbh, Matthias Fuchs <socketcan@esd.eu>
- * Copyright (C) 2022 esd electronics gmbh, Frank Jungclaus <frank.jungclaus@esd.eu>
+ * Copyright (C) 2022-2023 esd electronics gmbh, Frank Jungclaus <frank.jungclaus@esd.eu>
  */
-#include <linux/ethtool.h>
-#include <linux/signal.h>
-#include <linux/slab.h>
-#include <linux/module.h>
-#include <linux/netdevice.h>
-#include <linux/usb.h>
 
 #include <linux/can.h>
 #include <linux/can/dev.h>
 #include <linux/can/error.h>
+#include <linux/ethtool.h>
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/signal.h>
+#include <linux/slab.h>
+#include <linux/units.h>
+#include <linux/usb.h>
 
 MODULE_AUTHOR("Matthias Fuchs <socketcan@esd.eu>");
 MODULE_AUTHOR("Frank Jungclaus <frank.jungclaus@esd.eu>");
@@ -27,8 +28,8 @@ MODULE_LICENSE("GPL v2");
 #define USB_CANUSBM_PRODUCT_ID	0x0011
 
 /* CAN controller clock frequencies */
-#define ESD_USB2_CAN_CLOCK	60000000
-#define ESD_USBM_CAN_CLOCK	36000000
+#define ESD_USB2_CAN_CLOCK	(60 * MEGA) /* Hz */
+#define ESD_USBM_CAN_CLOCK	(36 * MEGA) /* Hz */
 
 /* Maximum number of CAN nets */
 #define ESD_USB_MAX_NETS	2
@@ -42,20 +43,21 @@ MODULE_LICENSE("GPL v2");
 #define CMD_IDADD		6 /* also used for IDADD_REPLY */
 
 /* esd CAN message flags - dlc field */
-#define ESD_RTR			0x10
+#define ESD_RTR	BIT(4)
+
 
 /* esd CAN message flags - id field */
-#define ESD_EXTID		0x20000000
-#define ESD_EVENT		0x40000000
-#define ESD_IDMASK		0x1fffffff
+#define ESD_EXTID	BIT(29)
+#define ESD_EVENT	BIT(30)
+#define ESD_IDMASK	GENMASK(28, 0)
 
 /* esd CAN event ids */
 #define ESD_EV_CAN_ERROR_EXT	2 /* CAN controller specific diagnostic data */
 
 /* baudrate message flags */
-#define ESD_USB_UBR		0x80000000
-#define ESD_USB_LOM		0x40000000
-#define ESD_USB_NO_BAUDRATE	0x7fffffff
+#define ESD_USB_LOM	BIT(30) /* Listen Only Mode */
+#define ESD_USB_UBR	BIT(31) /* User Bit Rate (controller BTR) in bits 0..27 */
+#define ESD_USB_NO_BAUDRATE	GENMASK(30, 0) /* bit rate unconfigured */
 
 /* bit timing CAN-USB/2 */
 #define ESD_USB2_TSEG1_MIN	1
@@ -70,7 +72,7 @@ MODULE_LICENSE("GPL v2");
 #define ESD_USB2_BRP_MIN	1
 #define ESD_USB2_BRP_MAX	1024
 #define ESD_USB2_BRP_INC	1
-#define ESD_USB2_3_SAMPLES	0x00800000
+#define ESD_USB2_3_SAMPLES	BIT(23)
 
 /* esd IDADD message */
 #define ESD_ID_ENABLE		0x80
@@ -128,7 +130,7 @@ struct rx_msg {
 	__le32 ts;
 	__le32 id; /* upper 3 bits contain flags */
 	union {
-		u8 data[8];
+		u8 data[CAN_MAX_DLEN];
 		struct {
 			u8 status; /* CAN Controller Status */
 			u8 ecc;    /* Error Capture Register */
@@ -145,7 +147,7 @@ struct tx_msg {
 	u8 dlc;
 	u32 hnd;	/* opaque handle, not used by device */
 	__le32 id; /* upper 3 bits contain flags */
-	u8 data[8];
+	u8 data[CAN_MAX_DLEN];
 };
 
 struct tx_done_msg {