loader: c_init returns 0 or 1

c_init returns 0 (success) or 1 (failure). Don't return other values.

Sponsored by: Netflix

libsa: Remove redundant sys/cdefs.h

Sponsored by: Netflix

Use 115200 bps by default for serial communication

9600 was a standard baud rate decades ago, but 115200 is now more common
so choose defaults that are useful to the largest number of users.

Note that boot0sio does not support rates above 9600 so it remains
unchanged.

Reviewed by: bz, imp, manu
Relnotes: Yes
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D36295

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

stand: efi create eficom console device.

Fix the 'renaming kludge' that we absolutely cannot do going forward
(it's cost us days of engineering time).

console=comconsole talks to the hardware directly. This is available
only on amd64. It is not available anywhere else (and so requires
changes for people doing comconsole on aarch64)

console=eficom talks to the console via EFI protocols. It's available
on amd64, aarch64 and riscv64. It's the first port that we find, though
it can be overriden by efi_com_port (which should be set to the UID of
the serial port, not the I/O port, despite the name). devinfo -v
will give the UID to uartX mapping.

This is an incompatible change for HYPER-V on amd64. It only works with
eficom console, so you'll need to change your configuration in
loader.conf. No compatibility hack will ever be provided for this (since
it requires renamig, which the loader cannot reliably do).

It's also an incompatible change for aarch64. comconsole will need to
change to eficom. There might be a comconsole "shim" for this.

All the interlock to keep only eficom and comconsole from both attaching
have been removed.

RelNotes: Yes
Sponsored by: Netflix
Discussed with: kevans
Differential Revision: https://reviews.freebsd.org/D39982

loader: comconsole: don't unconditionally wipe out hw.uart.console

It may be the case that we need to set hw.uart.console manually in some
scenarios that comconsole can't necessarily support. Avoid clobbering
hw.uart.console unless we've actually selected comconsole so that one
could at least get kernel console output..

Discussed with: imp
Sponsored by: Zenith Electronics LLC
Sponsored by: Klara, Inc.

amd64 loader: Use efiserialio for Hyper-V booted systems

UEFI provides ConIn/ConOut handles for consoles that it supports,
which include the text-video and serial ports. When the serial port
is available, use the UEFI driver instead of direct io-port accesses
to avoid conflicts between the firmware and direct hardware access, as
happens on Hyper-V (Azure) setups.

This change enables efiserialio to be built for efi-amd64 and has
higher order priority vs comconsole, and only uses efiserialio
if the hypervisor is Hyper-V. When efiserialio successfully
probes, it will set efi_comconsole_avail=true which will prevent
comconsole from probing in this setup.

Tested on Hyper-V, ESXi and Azure VMs.

PR: 264267
Reviewed by: kevans, whu
Tested by: whu
Obtained from: Rubicon Communications, LLC (Netgate)
MFC after: 2 weeks
Sponsored by: Rubicon Communications, LLC (Netgate)

test if port does exist via using scratch register

The SCR, scratch register was not present on the 8250 and 8250B UART, so we
can use to test if we actually do have serial port.

We need this test because some systems will get long delays while attempting
to write to non-existing port and this will slow down the console IO
to extreme.

MFC after: 1 week

loader: libi386/comconsole.c cstyle cleanup

Only cstyle, no functional changes.

We don't support configuring serial PCI cards in EFI. Make this clearer in the
source rather than obfuscaring it behind NO_PCI (nothing else declares that,
so it's not making the ifdefs clearer).

Invent new #defines for the biospci_{read,write}_config function to
specify the width and use them everywhere.

Sponsored by: Netflix

Handle misconfigured/nonexistent pcidev for comconsole instead of BTX panic.

PR: 203319
Reviewed by: imp jhb
MFC after: 2 weeks
Sponsored by: Limelight Networks
Differential Revision: https://reviews.freebsd.org/D13776

Move sys/boot to stand. Fix all references to new location

Sponsored by: Netflix