lpc176x: Move chip id code from usbserial.c to new file chipid.c

Add a chipid.c file - this makes the code layout more similar to the
other arm boards.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/lpc176x/chipid.c

@@ -0,0 +1,46 @@
+// Support for extracting the hardware chip id on lpc176x
+//
+// Copyright (C) 2019  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "autoconf.h" // CONFIG_USB_SERIAL_NUMBER_CHIPID
+#include "generic/irq.h" // irq_disable
+#include "generic/usb_cdc.h" // usb_fill_serial
+#include "generic/usbstd.h" // usb_string_descriptor
+#include "sched.h" // DECL_INIT
+
+// IAP interface
+#define IAP_LOCATION        0x1fff1ff1
+#define IAP_CMD_READ_UID    58
+#define IAP_UID_LEN         16
+typedef void (*IAP)(uint32_t *, uint32_t *);
+
+static struct {
+    struct usb_string_descriptor desc;
+    uint16_t data[IAP_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;
+
+    uint32_t iap_cmd_uid[5] = {IAP_CMD_READ_UID, 0, 0, 0, 0};
+    uint32_t iap_resp[5];
+    IAP iap_entry = (IAP)IAP_LOCATION;
+    irq_disable();
+    iap_entry(iap_cmd_uid, iap_resp);
+    irq_enable();
+
+    usb_fill_serial(&cdc_chipid.desc, ARRAY_SIZE(cdc_chipid.data)
+                    , &iap_resp[1]);
+}
+DECL_INIT(chipid_init);