gnop(8): add the ability to set a nop provider's physical path

[asomers]

Summary

gnop(8): add the ability to set a nop provider's physical path

While I'm here, expand the existing tests a bit.

Test Plan

ATF tests added

[asomers]

@brd this enhancement should allow us to replace all of the SAS phy stuff in the ZFS test suite. After that, the test suite won't require a SAS expander, or even physical hardware. It should be able to run in a VM.

sbin/geom/class/nop/geom_nop.c

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(On Diff #36891)

Is there a better letter I should've used? p and P were both taken, and geom's option parser restricts me to short options.

sys/geom/nop/g_nop.h

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(On Diff #36891)

Note that this flag prevents someone from setting the physical path to any string that begins with \255. But only a psychopath would want to do that.

tests/sys/geom/class/nop/nop_test.sh

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(On Diff #36891)

Renamed this test because it isn't about diskinfo(8); it's about geom(4).

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(On Diff #36891)

Some props, like physical path, can't be set on an md(4) device, so I added this test to cover them.

[asomers]

@mav this is the first GEOM class that needs to be changed in order to fix physpath handling, as we discussed. The tests for every other GEOM class will depend on this.

[rpokala]

I don't understand the G_NOP_PHYSPATH_PASSTHROUGH stuff. Can't you just check for non-NULL or non-empty 'physpath' being passed in?

[asomers]

In D13579#289073, @rpokala wrote:

I don't understand the G_NOP_PHYSPATH_PASSTHROUGH stuff. Can't you just check for non-NULL or non-empty 'physpath' being passed in?

I tried that first. The problem is that it prevents you from creating a gnop device with a blank physical path on top of a device with a non-blank physical path. I needed some non-NULL sentinel.