Implement -P for boot loader.

[imp]

Summary

It's a bit easier to implement here than in boot1, like is normally
done. When a keyboard appears in the UEFI device tree, assume -D -h,
just like on a BIOS boot.

1. It is unclear if an ACPI keyboard appearing in the tree means there's
2. a real keyboard or not. A USB keyboard doesn't seem to appear unless
3. it is really there.

[allanjude]

sys/boot/efi/loader/main.c

108

typo (handles)

125

typo (each)

[emaste]

Looks good to me (did not review the has_keboard implementation in minute detail).

sys/boot/efi/loader/main.c

153

This comment seems incomplete, or partially redundant.

[smh]

head/sys/boot/efi/loader/main.c

116 ↗

(On Diff #13132)

looks like an unrequired wrap given the lines above / below.

119 ↗

(On Diff #13132)

You could also return here.

122 ↗

(On Diff #13132)

style(9) missing braces.

130 ↗

(On Diff #13132)

The following is simpler to understand IMO:

nhandles = sz / sizeof(*hin);
for (i = 0; i < nhandles; i++) {
     status = BS->HandleProtocol(hin[i], &devid, (VOID **)&path);

140 ↗

(On Diff #13132)

typo?
"unclear if there's" ?

144 ↗

(On Diff #13132)

You could use IsDevicePathType here.

150 ↗

(On Diff #13132)

What are these magic constants and can we get some defines for them, so they aren't?

160 ↗

(On Diff #13132)

As above, but might be nice to also introduce an IsDevicePathSubType too.

177 ↗

(On Diff #13132)

style(9) brace return value

202 ↗

(On Diff #13132)

BOOL ?

249 ↗

(On Diff #13132)

style(9) int is not a bool.