Drise@Drise-Laptop ~/rockbox
$ patch --binary -p1 < as3525v2-usb.diff
patching file firmware/export/config/sansaclipplus.h
patching file firmware/export/config/sansafuzev2.h
patching file firmware/target/arm/as3525/usb-drv-as3525v2.c
patching file firmware/usbstack/usb_storage.c

Drise@Drise-Laptop ~/rockbox
$ patch --binary -p1 < as3525v2-enable-usb.diff
patching file firmware/export/config/sansaclipplus.h
Reversed (or previously applied) patch detected!  Assume -R? [n]
Apply anyway? [n] y
Hunk #1 FAILED at 179.
1 out of 1 hunk FAILED -- saving rejects to file firmware/export/config/sansaclipplus.h.rej
patching file firmware/export/config/sansafuzev2.h
Reversed (or previously applied) patch detected!  Assume -R? [n]
Apply anyway? [n] y
Hunk #1 FAILED at 193.
1 out of 1 hunk FAILED -- saving rejects to file firmware/export/config/sansafuz
ev2.h.rej