serialno: Refactored the serial number code, cleaning up its API and localising implementation details

src/command.c

@@ -608,8 +608,7 @@ static bool cmd_traceswo(target *t, int argc, const char **argv)
 	traceswo_init(swo_channelmask);
 #endif
 
-	char serial_no[DFU_SERIAL_LENGTH];
-	serial_no_read(serial_no);
+	serial_no_read();
 	gdb_outf("Trace enabled for BMP serial %s, USB EP 5\n", serial_no);
 	return true;
 }

src/include/serialno.h

@@ -20,7 +20,12 @@
 #ifndef __SERIALNO_H
 #define __SERIALNO_H
 
-char *serial_no_read(char *s);
-
+#ifndef DFU_SERIAL_LENGTH
+#define DFU_SERIAL_LENGTH
 #endif
 
+extern char serial_no[DFU_SERIAL_LENGTH];
+
+void serial_no_read(void);
+
+#endif

src/platforms/common/usb.c

@@ -26,7 +26,6 @@
 #include "cdcacm.h"
 #include "serialno.h"
 
-char serial_no[DFU_SERIAL_LENGTH];
 usbd_device *usbdev = NULL;
 
 /* We need a special large control buffer for this device: */
@@ -34,7 +33,7 @@ static uint8_t usbd_control_buffer[256];
 
 void blackmagic_usb_init(void)
 {
-	serial_no_read(serial_no);
+	serial_no_read();
 
 	usbdev = usbd_init(&USB_DRIVER, &dev_desc, &config, usb_strings, sizeof(usb_strings) / sizeof(char *),
 		usbd_control_buffer, sizeof(usbd_control_buffer));

src/platforms/common/usb_descriptors.h

@@ -26,12 +26,11 @@
 #include <libopencm3/usb/dfu.h>
 
 #include "usb.h"
+#include "serialno.h"
 #include "version.h"
 
 #define BOARD_IDENT "Black Magic Probe " PLATFORM_IDENT FIRMWARE_VERSION
 
-extern char serial_no[DFU_SERIAL_LENGTH];
-
 /* Top-level device descriptor */
 static const struct usb_device_descriptor dev_desc = {
 	.bLength = USB_DT_DEVICE_SIZE,

src/platforms/launchpad-icdi/platform.c

@@ -30,6 +30,7 @@
 
 extern void trace_tick(void);
 
+char serial_no[DFU_SERIAL_LENGTH];
 volatile platform_timeout * volatile head_timeout;
 uint8_t running_status;
 static volatile uint32_t time_ms;
@@ -115,19 +116,18 @@ const char *platform_target_voltage(void)
 	return NULL;
 }
 
-char *serial_no_read(char *s)
+void serial_no_read(void)
 {
 	/* FIXME: Store a unique serial number somewhere and retreive here */
 	uint32_t unique_id = SERIAL_NO;
 
 	/* Fetch serial number from chip's unique ID */
 	for (size_t i = 0; i < DFU_SERIAL_LENGTH - 1; i++) {
-		s[7U - i] = ((unique_id >> (4 * i)) & 0x0FU) + '0';
-		if (s[7U - i] > '9')
-			s[7U - i] += 7; /* 'A' - '9' = 8, less 1 gives 7. */
+		serial_no[7U - i] = ((unique_id >> (4 * i)) & 0x0FU) + '0';
+		if (serial_no[7U - i] > '9')
+			serial_no[7U - i] += 7; /* 'A' - '9' = 8, less 1 gives 7. */
 	}
-	s[DFU_SERIAL_LENGTH - 1] = 0;
-	return s;
+	serial_no[DFU_SERIAL_LENGTH - 1] = 0;
 }
 
 void platform_request_boot(void) { }

src/platforms/stm32/dfucore.c

@@ -53,7 +53,7 @@ static uint32_t max_address;
 
 static enum dfu_state usbdfu_state = STATE_DFU_IDLE;
 
-static char *get_dev_unique_id(char *serial_no);
+static void get_dev_unique_id(void);
 
 static struct {
 	uint8_t buf[sizeof(usbd_control_buffer)];
@@ -125,7 +125,6 @@ const struct usb_config_descriptor config = {
 	.interface = ifaces,
 };
 
-static char serial_no[DFU_SERIAL_LENGTH];
 static char if_string[] = DFU_IFACE_STRING;
 #define BOARD_IDENT_DFU(BOARD_TYPE) "Black Magic Probe DFU " PLATFORM_IDENT  "" FIRMWARE_VERSION
 
@@ -291,7 +290,7 @@ static enum usbd_request_return_codes usbdfu_control_request(usbd_device *dev,
 
 void dfu_init(const usbd_driver *driver)
 {
-	get_dev_unique_id(serial_no);
+	get_dev_unique_id();
 
 	usbdev = usbd_init(driver, &dev_desc, &config,
 			   usb_strings, 4,
@@ -337,7 +336,7 @@ static void set_dfu_iface_string(uint32_t size)
 # define set_dfu_iface_string(x)
 #endif
 
-static char *get_dev_unique_id(char *s)
+static void get_dev_unique_id(void)
 {
 	uint32_t fuse_flash_size;
 
@@ -348,5 +347,5 @@ static char *get_dev_unique_id(char *s)
 		fuse_flash_size = 0x80;
 	set_dfu_iface_string(fuse_flash_size - 8);
 	max_address = FLASH_BASE + (fuse_flash_size << 10);
-	return serial_no_read(s);
+	serial_no_read();
 }

src/platforms/stm32/serialno.c

@@ -20,17 +20,19 @@
 #include "general.h"
 #include <libopencm3/stm32/desig.h>
 
-char *serial_no_read(char *s)
+char serial_no[DFU_SERIAL_LENGTH];
+
+void serial_no_read(void)
 {
 #if DFU_SERIAL_LENGTH == 9
 	const volatile uint32_t *const unique_id_p = (uint32_t *)DESIG_UNIQUE_ID_BASE;
 	const uint32_t unique_id = unique_id_p[0] + unique_id_p[1] + unique_id_p[2];
 	/* Fetch serial number from chip's unique ID */
 	for (size_t i = 0; i < 8U; ++i) {
-		s[7U - i] = ((unique_id >> (i * 4U)) & 0x0FU) + '0';
+		serial_no[7U - i] = ((unique_id >> (i * 4U)) & 0x0FU) + '0';
 		/* If the character is something above 9, then add the offset to make it ASCII A-F */
-		if (s[7U - i] > '9')
-			s[7U - i] += 7; /* 'A' - '9' = 8, less 1 gives 7. */
+		if (serial_no[7U - i] > '9')
+			serial_no[7U - i] += 7; /* 'A' - '9' = 8, less 1 gives 7. */
 	}
 #elif DFU_SERIAL_LENGTH == 13
 	/* Use the same serial number as the ST DFU Bootloader.*/
@@ -40,7 +42,7 @@ char *serial_no_read(char *s)
 #elif defined(STM32L0) || defined(STM32F0) || defined(STM32F3)
 	int offset = 5;
 #endif
-	sprintf(s, "%04X%04X%04X", uid[1] + uid[5], uid[0] + uid[4], uid[offset]);
+	sprintf(serial_no, "%04X%04X%04X", uid[1] + uid[5], uid[0] + uid[4], uid[offset]);
 #elif DFU_SERIAL_LENGTH == 25
 	const volatile uint32_t *const unique_id_p = (uint32_t *)DESIG_UNIQUE_ID_BASE;
 	uint32_t unique_id = 0;
@@ -50,15 +52,14 @@ char *serial_no_read(char *s)
 		const size_t idx = (chunk << 3U) + (7U - nibble);
 		if (nibble == 0)
 			unique_id = unique_id_p[chunk];
-		s[idx] = ((unique_id >> (nibble * 4U)) & 0x0F) + '0';
+		serial_no[idx] = ((unique_id >> (nibble * 4U)) & 0x0F) + '0';
 
 		/* If the character is something above 9, then add the offset to make it ASCII A-F */
-		if (s[idx] > '9')
-			s[idx] += 7; /* 'A' - '9' = 8, less 1 gives 7. */
+		if (serial_no[idx] > '9')
+			serial_no[idx] += 7; /* 'A' - '9' = 8, less 1 gives 7. */
 	}
 #else
 #WARNING "Unhandled DFU_SERIAL_LENGTH"
 #endif
-	s[DFU_SERIAL_LENGTH - 1] = '\0';
-	return s;
+	serial_no[DFU_SERIAL_LENGTH - 1] = '\0';
 }