compat_ioctl question

From: Paul Fulghum
Date: Thu Apr 26 2007 - 16:52:20 EST

I need to add ioctl translations for my driver to
allow 32 bit access on 64 bit systems.

After digging through the kernel code there seems to be
3 methods of doing this:

1. define compat_ioctl() file operation for device and
implement translation code in individual driver
2. add COMPATIBLE_IOCTL entry to include/linux/compat_ioctl.h
to mark an ioctl code as the same in any environment
3. add HANDLE_IOCTL entry to fs/compat_ioctl.c with translation code
implemented in the same file

There is no way to implement #1 for a tty driver without
modifying the kernel tty code to allow registration of a
compat_ioctl() handler.

#3 would put a lot of driver specific stuff in a common
kernel file. This method also seems to break if there
is an ioctl code collision.

All of these methods involve changes to code outside of my driver.


Before I spend a lot of time on this I need to know what the
officially sanctioned method is. I haven't found any definitive
documentation and a review of mailing list archives does not
suggest a prevailing opinion.

Does anyone have pointers on which way would be most likely
to be accepted as a patch?


Paul Fulghum
Microgate Systems, Ltd

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