diff options
Diffstat (limited to 'Documentation/ioctl')
| -rw-r--r-- | Documentation/ioctl/cdrom.txt | 2 | ||||
| -rw-r--r-- | Documentation/ioctl/ioctl-decoding.txt | 24 |
2 files changed, 25 insertions, 1 deletions
diff --git a/Documentation/ioctl/cdrom.txt b/Documentation/ioctl/cdrom.txt index 8ec32cc49eb..62d4af44ec4 100644 --- a/Documentation/ioctl/cdrom.txt +++ b/Documentation/ioctl/cdrom.txt @@ -735,7 +735,7 @@ CDROM_DISC_STATUS Get disc type, etc. Ok, this is where problems start. The current interface for the CDROM_DISC_STATUS ioctl is flawed. It makes the false assumption that CDs are all CDS_DATA_1 or all CDS_AUDIO, etc. - Unfortunatly, while this is often the case, it is also + Unfortunately, while this is often the case, it is also very common for CDs to have some tracks with data, and some tracks with audio. Just because I feel like it, I declare the following to be the best way to cope. If the CD has diff --git a/Documentation/ioctl/ioctl-decoding.txt b/Documentation/ioctl/ioctl-decoding.txt new file mode 100644 index 00000000000..bfdf7f3ee4f --- /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]) |