Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.
1 To decode a hex IOCTL code: 2 3 Most architectures use this generic format, but check 4 include/ARCH/ioctl.h for specifics, e.g. powerpc 5 uses 3 bits to encode read/write and 13 bits for size. 6 7 bits meaning 8 31-30 00 - no parameters: uses _IO macro 9 10 - read: _IOR 10 01 - write: _IOW 11 11 - read/write: _IOWR 12 13 29-16 size of arguments 14 15 15-8 ascii character supposedly 16 unique to each driver 17 18 7-0 function # 19 20 21 So for example 0x82187201 is a read with arg length of 0x218, 22 character 'r' function 1. Grepping the source reveals this is: 23 24 #define VFAT_IOCTL_READDIR_BOTH _IOR('r', 1, struct dirent [2])