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| author | Dave Jones <davej@redhat.com> | 2006-12-12 17:41:41 -0500 |
|---|---|---|
| committer | Dave Jones <davej@redhat.com> | 2006-12-12 17:41:41 -0500 |
| commit | c4366889dda8110247be59ca41fddb82951a8c26 (patch) | |
| tree | 705c1a996bed8fd48ce94ff33ec9fd00f9b94875 /Documentation/ioctl/ioctl-decoding.txt | |
| parent | db2fb9db5735cc532fd4fc55e94b9a3c3750378e (diff) | |
| parent | e1036502e5263851259d147771226161e5ccc85a (diff) | |
Merge ../linus
Conflicts:
drivers/cpufreq/cpufreq.c
Diffstat (limited to 'Documentation/ioctl/ioctl-decoding.txt')
| -rw-r--r-- | Documentation/ioctl/ioctl-decoding.txt | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/Documentation/ioctl/ioctl-decoding.txt b/Documentation/ioctl/ioctl-decoding.txt new file mode 100644 index 000000000000..bfdf7f3ee4f0 --- /dev/null +++ b/Documentation/ioctl/ioctl-decoding.txt @@ -0,0 +1,24 @@ +To decode a hex IOCTL code: + +Most architecures 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]) |