194 lines
8.5 KiB
Markdown
194 lines
8.5 KiB
Markdown
# Welcome to the coreboot documentation
|
|
|
|
This is the developer documentation for [coreboot](https://coreboot.org).
|
|
It is built from Markdown files in the
|
|
[Documentation](https://review.coreboot.org/cgit/coreboot.git/tree/Documentation)
|
|
directory in the source code.
|
|
|
|
## Purpose of coreboot
|
|
|
|
coreboot is a project to develop open source boot firmware for various
|
|
architectures. Its design philosophy is to do the bare minimum necessary to
|
|
ensure that hardware is usable and then pass control to a different program
|
|
called the _payload_.
|
|
|
|
### Separation of concerns
|
|
|
|
The payload can then provide user interfaces, file system drivers,
|
|
various policies etc. to load the OS. Through this separation of concerns
|
|
coreboot maximizes reusability of the complicated and fundamental hardware
|
|
initialization routines across many different use cases, no matter if
|
|
they provide standard interfaces or entirely custom boot flows.
|
|
|
|
Popular [payloads](payloads.md) in use with coreboot are SeaBIOS,
|
|
which provides PCBIOS services, Tianocore, which provides UEFI services,
|
|
GRUB2, the bootloader used by many Linux distributions, or depthcharge,
|
|
a custom boot loader used on Chromebooks.
|
|
|
|
### No resident services (if possible)
|
|
|
|
Ideally coreboot completely hands over control to the payload with no
|
|
piece of coreboot remaining resident in the system, or even available
|
|
for callback. Given the reality of contemporary computer design,
|
|
there's often a small piece that survives for the whole runtime of
|
|
the computer. It runs in a highly privileged CPU mode (e.g. SMM on x86)
|
|
and provides some limited amount of services to the OS. But here, too,
|
|
coreboot aims to keep everything at the minimum possible, both in scope
|
|
(e.g. services provided) and code size.
|
|
|
|
### No specification of its own
|
|
|
|
coreboot uses a very minimal interface to the payload, and otherwise
|
|
doesn't impose any standards on the ecosystem. This is made possible by
|
|
separating out concerns (interfaces and resident services are delegated
|
|
to the payload), but it's also a value that is deeply ingrained in the
|
|
project. We fearlessly rip out parts of the architecture and remodel it
|
|
when a better way of doing the same was identified.
|
|
|
|
That said, since there are attempts to coerce coreboot to move in various
|
|
directions by outside "standardization", long-established practices of
|
|
coreboot as well as aligned projects can be documented as best practices,
|
|
making them standards in their own right. However we reserve the right to
|
|
retire them as the landscape shifts around us.
|
|
|
|
### One tree for everything
|
|
|
|
Another difference to various other firmware projects is that we try
|
|
to avoid fragmentation: the traditional development model of firmware
|
|
is one of "set and forget" in which some code base is copied, adapted
|
|
for the purpose at hands, shipped and only touched again if there's an
|
|
important fix to do.
|
|
|
|
All newer development happens on another copy of some code base without
|
|
flowing back to any older copy, and so normally there's a huge amount
|
|
of fragmentation.
|
|
|
|
In coreboot, we try to keep everything in a single source tree, and
|
|
lift up older devices when we change something fundamentally. That way,
|
|
new and old devices benefit alike from new development in the common parts.
|
|
|
|
There's a downside to that: Some devices might have no maintainer anymore
|
|
who could ensure that coreboot is still functional for them after a big
|
|
rework, or maybe a rework even requires knowledge that doesn't exist
|
|
anymore within the project (for example because the developer moved on
|
|
to do something else).
|
|
|
|
In this case, we announce the deprecation of the device and defer the big
|
|
rework until the deprecation period passed, typically 6-12 months. This
|
|
gives interested developers a chance to step in and bring devices up to
|
|
latest standards.
|
|
|
|
While without this deprecation mechanism we could inflate the number
|
|
of supported devices (probably 300+), only a tiny fraction of them
|
|
would even work, which helps nobody.
|
|
|
|
## Scope of the coreboot project
|
|
|
|
coreboot as a project is closer to the Linux kernel than to most
|
|
user level programs. One place where this becomes apparent is the
|
|
distribution mechanism: The project itself only provides source code
|
|
and does not ship ready-to-install coreboot-based firmware binaries.
|
|
|
|
What the project distributes, even if - strictly speaking - it's not
|
|
part of the project, is a collection of vendor binaries (that we call
|
|
"blobs") that are redistributable. They cover the parts of hardware init
|
|
that we haven't managed to open up, and while some hardware requires them,
|
|
there's still hardware that can boot without any such binary components.
|
|
|
|
The build system can integrate them into the build automatically if
|
|
required, but that requires explicit opt-in and downloads a separate
|
|
repository to ensure that the distinction remains clear.
|
|
|
|
There are various [distributions](distributions.md), some shipping
|
|
coreboot with their hardware (e.g. Purism or Chromebooks), others
|
|
providing after-market images for various devices (e.g. Libreboot,
|
|
MrChromebox).
|
|
|
|
If you want to use coreboot on your system, that's great!
|
|
|
|
Please note that the infrastructure around coreboot.org is built for
|
|
development purposes. We gladly help out users through our communication
|
|
channels, but we also expect a "firmware developer mindset": If compiling
|
|
your own firmware and, at some point, recovering from a bad flash by
|
|
hooking wires onto chips in your computer sounds scary to you, you're
|
|
right, as it is.
|
|
|
|
If that's _way_ beyond your comfort zone, consider looking into the
|
|
various distributions, as they typically provide pre-tested binaries
|
|
which massively reduces the risk that the binary you write to flash is
|
|
one that won't boot the system (with the consequence that to get it to work
|
|
again, you'll need to attach various tools to various chips)
|
|
|
|
## The coreboot community
|
|
|
|
If you're interested in getting your hands dirty (incl. potentially wiring
|
|
up an external flasher to your computer), you've come to the right place!
|
|
|
|
We have various [forums](community/forums.md) where we discuss and coordinate
|
|
our activities, review patches, and help out each other. To
|
|
help promote a positive atmosphere, we established a [Code of
|
|
Conduct](community/code_of_conduct.md). We invested a lot of time
|
|
to balance it out, so please keep it in mind when engaging with the
|
|
coreboot community.
|
|
|
|
Every now and then, coreboot is present in one way or another at
|
|
[conferences](community/conferences.md). If you're around, come and
|
|
say hello!
|
|
|
|
## Getting the source code
|
|
|
|
coreboot is primarily developed in the
|
|
[git](https://review.coreboot.org/cgit/coreboot.git) version control
|
|
system, using [Gerrit](https://review.coreboot.org) to manage
|
|
contributions and code review.
|
|
|
|
In general we try to keep the `master` branch in the repository functional
|
|
for all hardware we support. So far, the only guarantee we can make is
|
|
that the master branch will (nearly) always build for all boards in a
|
|
standard configuration.
|
|
|
|
However, we're continually working on improvements to our infrastructure to
|
|
get better in that respect, e.g. by setting up boot testing facilities. This
|
|
is obviously more complex than regular integration testing, so progress
|
|
is slow.
|
|
|
|
### What our releases mean
|
|
|
|
We also schedule two source code releases every year, around April and
|
|
October. These releases see some very limited testing and mostly serve
|
|
as synchronization points for deprecation notices and for other projects
|
|
such as external distributions.
|
|
|
|
This approach and terminology differs somewhat from how other projects handle
|
|
releases where releases are well-tested artifacts and the development
|
|
repository tends to be unstable. The "rolling release" model of some projects,
|
|
for example OpenBSD, is probably the closest cousin of our approach.
|
|
|
|
Contents:
|
|
|
|
* [Getting Started](getting_started/index.md)
|
|
* [Tutorial](tutorial/index.md)
|
|
* [Contributing](contributing/index.md)
|
|
* [Community](community/index.md)
|
|
* [Payloads](payloads.md)
|
|
* [Distributions](distributions.md)
|
|
* [Technotes](technotes/index.md)
|
|
* [ACPI](acpi/index.md)
|
|
* [Native Graphics Initialization with libgfxinit](gfx/libgfxinit.md)
|
|
* [Display panel](gfx/display-panel.md)
|
|
* [CPU Architecture](arch/index.md)
|
|
* [Platform independent drivers](drivers/index.md)
|
|
* [Northbridge](northbridge/index.md)
|
|
* [System on Chip](soc/index.md)
|
|
* [Mainboard](mainboard/index.md)
|
|
* [Payloads](lib/payloads/index.md)
|
|
* [Libraries](lib/index.md)
|
|
* [Options](lib/option.md)
|
|
* [Security](security/index.md)
|
|
* [SuperIO](superio/index.md)
|
|
* [Vendorcode](vendorcode/index.md)
|
|
* [Utilities](util.md)
|
|
* [coreboot infrastructure](infrastructure/index.md)
|
|
* [Release notes for past releases](releases/index.md)
|
|
* [Flashing firmware tutorial](flash_tutorial/index.md)
|