Don't return IIC_Exxxxx status values to userspace

[thj]

Summary

iiconf.h states:

/*

• Note that all iicbus functions return IIC_Exxxxx status values,
• except iic2errno() (obviously) and iicbus_started() (returns bool). */

however iic.c returns a mixture of ERRNO values and IIC_Exxxxx values in ioctl and read calls. Attempt to translate
these calls with iic2errno.

[thj]

Recreate diff using svn diff --diff-cmd=diff -x -U999999 > change.diff

[mat]

All these:

error = foo(bar);
error = iic2errno(error);

feel a bit strange. Wouldn't it be better to write:

error = iic2errorno(foo(bar));

[thj]

Wrap calls with iic2errno converter

[• ian]

Unfortunately, the comment that says "all iicbus functions return IIC_Exxxxx status values" is incorrect. There is one exception which screws up this whole error-translation thing: iicbus_poll() can return an errno and the rather important errno values it might return, EINTR and ERESTART, have no corresponding IIC_Exxxxx value they could be translated to so that they can later be translated back.

I have long believed that the right fix for this whole mess is to eliminate the IIC_Exxxxx stuff and just use errnos everywhere. But that's a hard change to make, especially considering there might be out-of-tree drivers.

A much simpler fix would be to add IIC_ERESTART and IIC_EINTR, and I guess something like IIC_EOTHER or maybe IIC_ESYSERR, some kind of catch-all that just means "I got an error from some system thing that isn't directly related to the iic protocol". Then iicbus_poll() could translate the errno from mtx_sleep() to an IIC_Exxxx that would then later be properly translated back to an errno. Ick, but it preserves KPI and KBI.

Note that I haven't yet done a detailed review of the code changes in the current diff.

[• ian]

Upon further reflection, I think the changes to iic(4) in this diff are correct and should be committed. The problem of iicbus_request_bus() returning an ambiguous mix of IIC_Exxxxx or errno values because of iicbus_poll() doing so is a separate problem and should be fixed separately.