psm(4), evdev support part 2: psm softc locking

[wulf_cicgroup.ru]

Summary

psm(4): Serialize softc access with mutex.
Mark interrupt and cdev handlers MPSAFE

Part of https://reviews.freebsd.org/D10207

[gonzo]

It looks OK to me but could you email link to this review to freebsd-arch@ and ask for second opinion? With code this old there might be some hidden pitfalls. If nobody raises any concerns - go ahead and commit it.

[wulf_cicgroup.ru]

could you email link to this review to freebsd-arch@

I will do that

[wulf_cicgroup.ru]

Change is obsolete.
After some discussion with bde@ (on arch@ and private) it is turned out that nothing but Giant can be used to serialize access to I8042 ports currently.
Although it is possible to move psm softc from Giant to private mutex that would complicate things as all calls to I8042 should be done with Giant taken so psm mutex should be released at this time.

[gonzo]

Vladimir, could you abandon this change if it's obsolete and you don't have any plans to update the patch?

Thanks

[wulf_cicgroup.ru]

Finally I found out how to abandon revision after some googling. It is not very intuitive.