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 ↗

(On Diff #13102)

typo (handles)

125 ↗

(On Diff #13102)

typo (each)

[emaste]

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

sys/boot/efi/loader/main.c

153 ↗

(On Diff #13102)

This comment seems incomplete, or partially redundant.

[smh]

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

116

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

119

You could also return here.

122

style(9) missing braces.

130

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

typo?
"unclear if there's" ?

144

You could use IsDevicePathType here.

150

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

160

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

177

style(9) brace return value

202

BOOL ?

249

style(9) int is not a bool.