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Signed-off-by: Leah Rowe <info@minifree.org>
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Leah Rowe 2024-11-29 08:00:13 +00:00
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@ -133,6 +133,79 @@ In other words, do not lecture the user. Just try to help them with their
problem! The goal of the libreboot project is simply to make coreboot more
accessible for otherwise non-technical users.
Examples of Libreboot policy in action
======================================
More information about this is also available on
the [freedom status](freedom-status.md) page.
Context is everything, so to make the above picture more clear, here are a few
examples of how this very policy is implemented in Libreboot:
* On many laptops, it is possible to have both Intel graphics and a dedicated
graphics card enabled; more about Intel graphics is covered below. We could
provide the VGA ROM for those extra chips, e.g. Nvidia graphics chips, but
we don't. We configure the machines in such a way where the Intel graphics
is used, exclusively, so the dedicated GPU may aswell be turned off, and
it *is* turned off in such circumstances. The Intel graphics provide good
enough performance and reliable operation for most people, and native
initialisation code is available from coreboot to make use of the Intel GPU
at boot time.
* Newer Intel platforms have Intel ME, which is a coprocessor inside the
machine that handles many functions including certain power management, and
it can provides useful remote management features with Intel AMT for example.
This is a giant 5MB+ blob in the flash, and the ME has full access to your
RAM and other peripherals; more is documented about this in the Libreboot
FAQ. On older ME4-based platforms such as Intel GM45 platforms, e.g.
ThinkPad X200/T400, we remove the ME firmware entirely from the flash, leaving
the Intel ME in a permanent reset loop. On Intel Sandybridge and up, we
include ME firmware when building, or provide a script to insert it via
vendor download on release images, but Libreboot's build system automatically
runs the [me cleaner](https://github.com/corna/me_cleaner) software, which
removes most of the features from the ME, including its kernel and networking
stack, leaving only a rump (dare we say, ROMP) of initialisation code in
the ME; essentially, the configuration is equivalent to running coreboot
without a payload, where it does nothing other than initialise itself, because
that is all the ME does in this configuration, initialise itself but not
actually run anything. ME Cleaner is required, instead of full removal,
because the machines don't boot reliably without at least the BUP/ROMP
modules present in flash.
* On Intel Haswell platform (Intel 4th gen), a binary blob is available for
memory controller initialisation, called the Intel *MRC* or System Agent. We
previously included this in Libreboot; nowadays, we have free initialisation
code written by Angel Pons. The libre code, called NRI (Native RAM
Initialisation) still has a few bugs, such as lack of ECC support, and the
MRC also does other things such as initialise certain peripherals. The
Haswell machines can be configured in EHCI or XHCI mode for USB ports at
startup, and the latter means that you need xHCI support in whatever you're
using such as Linux, but also payloads such as U-Boot or GRUB. SeaBIOS and
GRUB have stable xHCI support (we have to patch GRUB to have it because
otherwise upstream doesn't have it). U-Boot's xHCI support is quite buggy,
at least as of November 2024; when tested, it looks like the EHCI mode
doesn't work on NRI, only MRC. Now, to get more stable U-Boot support when
using USB devices, we could use the MRC and set the machine in EHCI mode
at startup; an option exists for it in coreboot. Ditto, we could have ECC
support (useful on the Dell Precision T1700, which Libreboot supports!) - it
was decided that these issues are quite minor so the free initialisation code
is used, and we no longer provide the MRC.
* Libreboot provides native graphics initialisation on most Intel hardware,
provided by coreboot. This replaces the Intel VGA ROM; called libgfxinit,
coreboot's native code is far from perfect because many legacy VGA functions
simply do not work so it can be a challenge to get old, legacy operating
systems working, even if they had full driver support on a given machine
when running the vendor BIOS. Libgfxinit otherwise provides a sensible
framebuffer implementation from coreboot, which Linux and BSD systems know
how to use, and you can use KMS on these systems instead of calls to VGA
in the BIOS, to mitigate this issue. It was decided a long time ago that,
when available, the native initialisation should be used, when it is stable
and Linux/BSD systems work reliably. There is only one exception: the
ThinkPad T480 currently doesn't work with libgfxinit in Libreboot, at least
as of November 2024, so the Intel VGA ROM is used instead.
* On RK3399-based Chromebooks, it is possible to load a HDCP blob, which could
be convenient for easy access to DRM-based media. We simply do not use this
blob on any machines, because it is completeley unnecessary for everyday
operating of a free operating system.
FREEDOM CATALOG
===============