input_event size mismatch between 64bit kernel and 32bit userland ...

Pavel Kiryukhin discovered this problem while he is developing 64bit MIPS kernel. With his permission I am forwarding this question to lkml and we would be interested to know how x86_64 solves this problem.

Thanks.

Jun

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Hi all,
I stuck in simple situation:
USB mouse (or keyboard). n64 kernel (2.4.20), n32 userland.

Userspace application tries to read "input_event" (16 bytes) from "/dev/input/event0" [ read(fd,&key_ev, sizeof(key_ev)) ], input core driver treats "input_event" as 24 bytes structure. It is due to different size of "timeval" (and finally "long") in n64 kernel and n32 userland.

Application gets some garbage as mouse events . No solutions like "ioctl wrappers" applicable in this case.

I don't want to change any arch independent files, but can not find any acceptable solution. It looks like headers "/usr/include/linux/input.h" in root file system and "/include/linux/input.h" in kernel should be the same,
(All works fine as soon as I declare a new "input_event" structure in
user application that corresponds in size to kernel structure - but this is not acceptable).

Can anybody advice me what to do with the difference in "input_event" structure sizes in o32/n32 userland and n64 kernel? Just a general approach that can be used when driver's read/write operation treat some values as 64 bit while user application tries to read/write 32-bit values (based on the same headers).

Please, don't kick me if solution is simple and obvious.

x86_64 doesn't solve this problem, it's broken there too

Some CONFIG_COMPAT code needs to be added to the input layer I guess