docs/install: note about different ROM image file names

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Leah Rowe 2021-05-23 21:50:52 +01:00
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@ -21,6 +21,98 @@ If you're already running libre firmware on your board, you should decide for
sure whether you wish to risk it. See changelogs on sure whether you wish to risk it. See changelogs on
the [release logs](../release.md) and decide for yourself. the [release logs](../release.md) and decide for yourself.
About ROM image file names
==========================
Init types and display mode
---------------------------
NOTE: On Libreboot 20210522, `libgfxinit` in the only init type provided on
the pre-compiled ROM images, but the build system does support other types
defined below.
NOTE: regardless of init type, on desktops, an external/add-on GPU can always
be used. On laptop hardware in Libreboot, libgfxinit will always be used. On
desktop/server hardware, if available, libgfxinit will also always be used by
default (but in that setup, SeaBIOS can be used if you want to use an add-on
graphics card, e.g. on KCMA-D8, KGPE-D16, GA-G41M-ES2L)
### libgfxinit
In this setup, on supported systems, coreboot's own native video initialization
code is used. This is referred to generically as libgfxinit, which is coreboot's
library in `3rdparty/libgfxinit` but not all boards with native video
initialization use libgfxinit; some of them are using coreboot's older style
of video initialization method, written purely in C.
#### corebootfb (libgfxinit)
high resolution coreboot framebuffer used on startup
#### txtmode (libgfxinit)
int10h text mode is used on startup.
### vgarom
NOTE: no configs in libreboot are currently available that use this method.
With this method, coreboot is finding, loading and executing a VGA option ROM
for your graphics hardware. This would not be done on laptops, because that
implies supplying non-free binary blobs in Libreboot, so this setup would only
ever be provided on desktop hardware where no GPU exists or where it is
desirable for you to use an external/add-on graphics card
#### vesafb (vgarom)
high resolution VESA framebuffer used on startup
#### txtmode (vgarom)
int10h text mode is used on startup
### normal
int10h text mode startup is implied here.
In this setup, coreboot is neither implementing libgfxinit / native graphics
initialization nor is it finding/loading/executing VGA option ROMs. In this
setup, SeaBIOS would most likely be used for that.
The `normal` setup is supported in the Libreboot 20210522 build system, but not
currently used. It is there for desktop hardware that will be added in the
future, where those desktop boards do not have an onboard GPU and therefore an
add-on GPU is always used..
Payload names
-------------
### grub
ROM images with just `grub` in the file name will start first with the GNU GRUB
payload. They may or may not also provide other payloads in the menu, such as
memtest86+, SeaBIOS, Tianacore and so on.
### seabios
ROM images with just `seabios` in the file name will start first with the
SeaBIOS payload. They will only contain SeaBIOS, but may also contain memtest as
an option in the boot menu.
### seabios\_withgrub
ROM images that have `seabios_withgrub` in the file name start with SeaBIOS
first, but also have GNU GRUB available in the boot menu when you press ESC.
### seabios\_grubfirst
ROM images that have `seabios_grubfirst` in the file name start with SeaBIOS,
but SeaBIOS is configured via special `bootorder` file in CBFS so as to ONLY
load GNU GRUB. This setup would be most useful on desktops, where you wish to
only have GNU GRUB available, but want to use an add-on GPU while also having
the option to use libgfxinit, if a supported GPU/framebuffer chip is present
on your board.
Which systems are supported? Which systems are supported?
============================ ============================