~/rockbox/rbutil/mkimxboot/./mkimxboot -i firmware.sb -b bootloader-fuzeplus.sansa -o patched.sb -t dualboot

[INFO] mkimxboot models:
[INFO]   (null): idx=0 rb_model=(null) rb_num=0
[INFO]   Fuze+: idx=1 rb_model=fuz+ rb_num=72
[INFO]   Zen X-Fi2: idx=2 rb_model=zxf2 rb_num=82
[INFO]   Zen X-Fi3: idx=3 rb_model=zxf3 rb_num=83
[INFO]   Zen X-Fi Style: idx=4 rb_model=zxfs rb_num=94
[INFO]   Zen Style 100/300: idx=5 rb_model= rb_num=-1
[INFO]   NWZ-E370: idx=6 rb_model=e370 rb_num=88
[INFO]   NWZ-E360: idx=7 rb_model=e360 rb_num=89
[INFO] mkimxboot variants:
[INFO]   0: default
[INFO]   1: ZEN X-Fi2 NAND
[INFO]   2: ZEN X-Fi2 eMMC/SD
[INFO]   3: ZEN X-Fi2 Recovery
[INFO]   4: ZEN X-Fi Style Recovery
[INFO]   5: ZEN Style 100/300 Recovery
[INFO] mkimxboot mapping:
[INFO]   md5sum=c3e27620a877dc6b200b97dcb3e0ecc7 -> idx=1, ver=2.38.6
[INFO]     variant=0 -> offset=0 size=0x210c1d0
[INFO]   md5sum=e37e2c24abdff8e624d0a29f79157850 -> idx=2, ver=1.23.01
[INFO]     variant=1 -> offset=0x13a0b0 size=0x28712d0
[INFO]     variant=2 -> offset=0x29ab380 size=0x28582d0
[INFO]     variant=3 -> offset=0x93010 size=0xa70a0
[INFO]   md5sum=2beff2168212d332f13cfc36ca46989d -> idx=2, ver=1.23.01e
[INFO]     variant=1 -> offset=0x13a0b0 size=0x28722d0
[INFO]     variant=2 -> offset=0x29ac380 size=0x28582d0
[INFO]     variant=3 -> offset=0x93010 size=0xa70a0
[INFO]   md5sum=658a24eeef5f7186ca731085d8822a87 -> idx=3, ver=1.00.15e
[INFO]     variant=0 -> offset=0 size=0x1145870
[INFO]   md5sum=a5114cd45ea4554ec221f51a71083862 -> idx=3, ver=1.00.22e
[INFO]     variant=0 -> offset=0 size=0x1145870
[INFO]   md5sum=a41a3a78f86a4ac2879d194c6d528059 -> idx=3, ver=1.00.25
[INFO]     variant=0 -> offset=0 size=0x1145870
[INFO]   md5sum=c180f57e2b2d62620f87a1d853f349ff -> idx=3, ver=1.00.25e
[INFO]     variant=0 -> offset=0 size=0x1145870
[INFO]   md5sum=32a731b7f714e9f99a95991003759c98 -> idx=4, ver=1.03.04
[INFO]     variant=0 -> offset=0xcdcd0 size=0x1c7e2d0
[INFO]     variant=4 -> offset=0x94fe0 size=0x38cf0
[INFO]   md5sum=2c7ee52d9984d85dd39aa49b3331e66c -> idx=4, ver=1.03.04e
[INFO]     variant=0 -> offset=0xcdcd0 size=0x1c7e2d0
[INFO]     variant=4 -> offset=0x94fe0 size=0x38cf0
[INFO]   md5sum=dbebec8fe666412061d9740ff68605dd -> idx=5, ver=1.03.04e
[INFO]     variant=0 -> offset=0xb9440 size=0x6556c0
[INFO]     variant=5 -> offset=0x94fe0 size=0x24460
[INFO]   md5sum=a615fdb70b3e1bfb0355a5bc2bf237ab -> idx=6, ver=1.00.00
[INFO]     variant=0 -> offset=0 size=0xf50000
[INFO]   md5sum=ee83f3c6026cbcc07097867f06fd585f -> idx=6, ver=1.00.01
[INFO]     variant=0 -> offset=0 size=0xfc0000
[INFO]   md5sum=d0047f8a87d456a0032297b3c802a1ff -> idx=7, ver=1.00.00
[INFO]     variant=0 -> offset=0 size=0x13b2000
[INFO]   md5sum=412f8ccd453195c0bebcc1fd8376322f -> idx=6, ver=1.00.00
[INFO]     variant=0 -> offset=0 size=0xfab000
[INFO]   md5sum=75cfa51078261c547717e11a4676f1af -> idx=6, ver=1.00.200
[INFO]     variant=0 -> offset=0 size=0xfab000
[INFO] MD5 sum of the file: c3e27620a877dc6b200b97dcb3e0ecc7
[INFO] File is for model 1 (Fuze+, version 2.38.6)
Result: -2 (open error)