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
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