iicbus: add compat32 support for I2C ioctls

[stevek]

Summary

Some of the I2C ioctl request structures contain pointers and need to
handle requests from 32-bit applications on 64-bit kernels.

Obtained from: Juniper Networks, Inc.

[jhb]

sys/dev/iicbus/iic.c

337–338

I would maybe use iic_ prefix for new functions.

361

Hmm, is the error -Wunused? I would maybe just use __unused instead in the function declaration.

[jhb]

sys/dev/iicbus/iic.c

521

Maybe similar to what you did in the SMB patch, use a single early switch to do the swabbing so that the code is shared between I2CREAD and I2CWRITE? I prefer that in general (doing all the swabbing before/after the "main" switch on the ioctl cmd) but was just going to let it go until I saw you did this already in the SMB case. :)

[stevek]

sys/dev/iicbus/iic.c

361

Yes, that's for -Wunused. I wasn't sure what is recommended when an argument is used in some cases, but not in others, dependent on defines. I'm fine with using __unused, if that's okay, even though it is used in the case of COMPAT_FREEBSD32 being defined.

[stevek]

Addressed comments from jhb

[stevek]

sys/dev/iicbus/iic.c

337–338

Note this was not a new function, just adding an argument. However, iiccopyinmsgs32 is new. I was following the naming convention in the file, but if you want iiccopyinmsgs32 to have iic_copyinmsgs32, I can do that.

[stevek]

Changed iiccopyinmsgs32 to iic_copyinmsgs32, per suggested comments

[jhb]

sys/dev/iicbus/iic.c

361

I think it's less ugly. If there were several of these variables you could define a new compat32_unused wrapper that is conditional on an #ifdef similar to what we've done for diagused for INVARIANTS, but for one variable the wrapper isn't worth it.