diff options
Diffstat (limited to 'bootloader')
| -rw-r--r-- | bootloader/ipod.c | 79 |
1 files changed, 71 insertions, 8 deletions
diff --git a/bootloader/ipod.c b/bootloader/ipod.c index d5da776..e5538b2 100644 --- a/bootloader/ipod.c +++ b/bootloader/ipod.c @@ -222,6 +222,61 @@ void fatal_error(void) } +/* The bootloader is started from the OSOS image on the firmware + * partition. There are several ways it can be installed there: + * appended to the Apple firmware, on its own, or appended to + * Rockbox itself. The Apple ROM loader loads the entire OSOS + * image to DRAM_START, whatever it contains. If the bootloader + * is appended to another image then it will've modified the + * entry point in the OSOS header such that the ROM will call the + * bootloader rather than the main image. + * + * So, once the bootloader has control: + * + * 1) If the hold switch is on, or the menu button is being held, + * try to boot the Apple firmware. + * 1a) First, it looks for apple_os.ipod on the FAT32 partition, + * in .rockbox or the root directory. If found it loads that + * without further checking and runs it. + * 1b) Next, it checks to see if the OSOS image already loaded + * into RAM is in fact the Apple firmware with the bootloader + * appended. It looks at DRAM_START+0x20 for the string + * "portalplayer", and if it's there, just jumps back to + * DRAM_START where the entry point was before the bootloader + * was appended. + * 1c) If neither of those worked, it displays an error and dies. + * + * 2) If the play button is being held, try to boot Linux. It looks + * for linux.bin in the root directory, and if it's not there, + * it displays an error and dies. + * + * 3) Otherwise, try to boot Rockbox. + * 3a) First, it looks for rockbox.ipod on the FAT32 partition, + * in .rockbox or the root directory. If found it loads that + * without further checking and runs it. + * 3b) Next, it checks to see if the OSOS image already loaded + * into RAM is in fact Rockbox with the bootloader appended. + * It looks at DRAM_START+0x20 for the string "Rockbox\1" + * (which is inserted there in crt0-pp.S), and if it's there, + * just humps back to DRAM_START where the entry point was + * before the bootloader was appended. + * 3c) If neither of those worked, it displays an error and dies. + * + * The result is that any of the three install configurations work, + * and that images of apple_os.ipod or rockbox.ipod on the FAT32 + * partition take priority over the contents of OSOS (this avoids + * upgrades failing to work if OSOS is not updated). + * + * Loading from OSOS is somewhat faster than loading from FAT32, + * because the Apple ROM doesn't have to deal with filesystems or + * fragmentation, and is already loading from OSOS anyway. Thus, + * the fastest boot configuration that still allows dual booting + * is to install Rockbox into OSOS with the bootloader appended + * (and delete/rename rockbox.ipod from the FAT32 partition). + * + * It is of course faster to just install Rockbox to OSOS alone, + * but then it's impossible to boot the Apple firmware. + */ void* main(void) { @@ -229,7 +284,7 @@ void* main(void) int i; int btn; int rc; - bool haveretailos; + bool haveramos; bool button_was_held; struct partinfo* pinfo; unsigned short* identify_info; @@ -319,8 +374,8 @@ void* main(void) } else if (rc == EFILE_NOT_FOUND) { /* If apple_os.ipod doesn't exist, then check if there is an Apple firmware image in RAM */ - haveretailos = (memcmp((void*)(DRAM_START+0x20),"portalplayer",12)==0); - if (haveretailos) { + haveramos = (memcmp((void*)(DRAM_START+0x20),"portalplayer",12)==0); + if (haveramos) { /* We have a copy of the retailos in RAM, lets just run it. */ return (void*)DRAM_START; } @@ -346,14 +401,22 @@ void* main(void) } else { printf("Loading Rockbox..."); rc=load_firmware(loadbuffer, BOOTFILE, MAX_LOADSIZE); - if (rc < EOK) { - printf("Error!"); - printf("Can't load " BOOTFILE ": "); - printf(strerror(rc)); - } else { + if (rc == EOK) { printf("Rockbox loaded."); return (void*)DRAM_START; + } else if (rc == EFILE_NOT_FOUND) { + /* if rockbox.ipod doesn't exist, then check if there is a Rockbox + image in RAM */ + haveramos = (memcmp((void*)(DRAM_START+0x20),"Rockbox\1",8)==0); + if (haveramos) { + /* We have a copy of Rockbox in RAM, lets just run it. */ + return (void*)DRAM_START; + } } + + printf("Error!"); + printf("Can't load " BOOTFILE ": "); + printf(strerror(rc)); } /* If we get to here, then we haven't been able to load any firmware */ |