| To decode a hex IOCTL code: | |
| Most architectures use this generic format, but check | |
| include/ARCH/ioctl.h for specifics, e.g. powerpc | |
| uses 3 bits to encode read/write and 13 bits for size. | |
| bits meaning | |
| 31-30 00 - no parameters: uses _IO macro | |
| 10 - read: _IOR | |
| 01 - write: _IOW | |
| 11 - read/write: _IOWR | |
| 29-16 size of arguments | |
| 15-8 ascii character supposedly | |
| unique to each driver | |
| 7-0 function # | |
| So for example 0x82187201 is a read with arg length of 0x218, | |
| character 'r' function 1. Grepping the source reveals this is: | |
| #define VFAT_IOCTL_READDIR_BOTH _IOR('r', 1, struct dirent [2]) |