stm32: Enable chipid as usb serial number

Signed-off-by: Matt Baker <baker.matt.j@gmail.com>
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/stm32/chipid.c

@@ -0,0 +1,33 @@
+// Support for extracting the hardware chip id on stm32
+//
+// Copyright (C) 2019  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "generic/usb_cdc.h" // usb_fill_serial
+#include "generic/usbstd.h" // usb_string_descriptor
+#include "internal.h" // UID_BASE
+#include "sched.h" // DECL_INIT
+
+#define CHIP_UID_LEN 12
+
+static struct {
+    struct usb_string_descriptor desc;
+    uint16_t data[CHIP_UID_LEN * 2];
+} cdc_chipid;
+
+struct usb_string_descriptor *
+usbserial_get_serialid(void)
+{
+   return &cdc_chipid.desc;
+}
+
+void
+chipid_init(void)
+{
+    if (!CONFIG_USB_SERIAL_NUMBER_CHIPID)
+        return;
+    usb_fill_serial(&cdc_chipid.desc, ARRAY_SIZE(cdc_chipid.data)
+                    , (void*)UID_BASE);
+}
+DECL_INIT(chipid_init);