Re: "Enhanced" MD code avaible for review

[Jeff Garzik <jgarzik@pobox.com>]

Andi Kleen wrote:
> Sorry, Jeff, but that's just not true. While ioctls need an additional
> entry in the conversion table, they can at least easily get an
> translation handler if needed. When they are correctly designed you
> just need a single line to enable pass through the emulation.
> If you don't want to add that line to the generic compat_ioctl.h
> file you can also do it in your driver.
> 
> read/write has the big disadvantage that if someone gets the emulation
> wrong (and that happens regularly) it is near impossible to add an 
> emulation handler then, because there is no good way to hook
> into the read/write paths.
> 
> There may be valid reasons to go for read/write, but 32bit emulation
> is not one of them. In fact from the emulation perspective read/write
> should be avoided.

I'll probably have to illustrate with code, but basically, read/write 
can be completely ignorant of 32/64-bit architecture, endianness, it can 
even be network-transparent.  ioctls just can't do that.

	Jeff