Initial commit for the Sony NWZ linux port

SUPPORTED SERIES:
- NWZ-E450
- NWZ-E460
- NWZ-E470
- NWZ-E580
- NWZ-A10

NOTES:
- bootloader makefile convert an extra font to be installed alongside the bootloader
  since sysfont is way too small
- the toolsicon bitmap comes from the Oxygen iconset
- touchscreen driver is untested

TODO:
- implement audio routing driver (pcm is handled by pcm-alsa)
- fix playback: it crashes on illegal instruction in DEBUG builds
- find out why the browser starts at / instead of /contents
- implement radio support
- implement return to OF for usb handling
- calibrate battery curve (NB: of can report a battery level on a 0-5 scale but
  probabl don't want to use that ?)
- implement simulator build (we need a nice image of the player)
- figure out if we can detect jack removal

POTENTIAL TODOS:
- try to build a usb serial gadget and gdbserver

Change-Id: Ic77d71e0651355d47cc4e423a40fb64a60c69a80

firmware/target/hosted/backtrace-glibc.c

@@ -0,0 +1,60 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (c) 2017 Amaury Pouly
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#include "config.h"
+#include "system.h"
+#include "lcd.h"
+#include <execinfo.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+/* backtrace from the call-site of this function */
+void rb_backtrace(int pc, int sp, unsigned *line)
+{
+    /* ignore SP and PC */
+    (void) pc;
+    (void) sp;
+
+    /* backtrace */
+    #define BT_BUF_SIZE 100
+    void *buffer[BT_BUF_SIZE];
+    int count = backtrace(buffer, BT_BUF_SIZE);
+    /* print symbols to stdout for debug */
+    fprintf(stdout, "backtrace:\n");
+    fflush(stdout);
+    backtrace_symbols_fd(buffer, count, STDOUT_FILENO);
+    /* print on screen */
+    char **strings;
+    strings = backtrace_symbols(buffer, count);
+    if(strings == NULL)
+    {
+        perror("backtrace_symbols");
+        return;
+    }
+
+    for(int i = 0; i < count; i++)
+    {
+        lcd_putsf(0, (*line)++, "  %s", buffer[i], strings[i]);
+        lcd_update();
+    }
+
+    free(strings);
+}