Messages in this thread | | | Date | Thu, 7 Dec 2006 20:42:58 -0800 | From | Randy Dunlap <> | Subject | Re: [patch] Document how to decode an IOCTL number |
| |
On Thu, 7 Dec 2006 23:02:04 -0500 Chuck Ebbert wrote:
> Document how to decode a binary IOCTL number. > > Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com> > --- > Documentation/ioctl/ioctl-decoding.txt | 24 ++++++++++++++++++++++++ > 1 file changed, 24 insertions(+)
Thanks... could this be added to Documentation/ioctl-number.txt instead? and maybe move that file into Documentation/ioctl/ ?
> --- /dev/null > +++ 2.6.19.0.5-32smp/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]) > --
--- ~Randy - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |