Stefan,
I think this is a reasonable idea, particularly your suggestion of making linuxbios more modular. One of my main beefs with the payload strategy is that each payload has to provide it's own set of, potentially buggy, driver code. If we have 5 payloads then we have 5 sets of drivers that all do the same thing slightly differently. If the drivers were modular enough so that a payload could call them directly, then this would go a long way to addressing these concerns.
Regards,
Greg
On Jun 8, 2004, at 4:49 AM, Stefan Reinauer wrote:
There has been a similar proposal on this list a while ago, but nothing happened so far, so I want to put this pack to discussion.
Objectives ----------
1.) LinuxBIOS is kind of hard to set up for project newbies, since it does not only require manually tweaking the configuration files for basically every situation, but also necessarily needs an external payload to do anything useful. LinuxBIOS currently sets a high barrier due to the modular concepts it uses.
- LinuxBIOS itself is sometimes very sensitive to the build environment. See requirement for setting LANG for example.
- For a project outsider it is hard to determine the best payload solution for a specific purpose. There is basically no information except the mailing list archives.
- Config files have to be tweaked to explicitly suit the user's directory structure. There is no proposal, nothing that works out of the box. One just _has to_ edit the config files.
- LinuxBIOS requires the user to specify a size for the payload instead
of determining the required size and doing the needed calculations
itself. This is very hand-crufted and can be pretty mind wasting.
2.)
LinuxBIOS can currently execute one payload. For greater flexibility and
isolated development cycles of the firmware related code parts/projects
LinuxBIOS should allow payload chains, ie. executing multiple payloads
one after the other.
LinuxBIOS wants to keep up it's modularity, letting each module do it's job. This possibility of not doing more than one task should be passed on to the payloads.
Solution --------
Feature plugins like "testbios" should not be merged into LinuxBIOS' core code. Instead they should be implemented as a payload. Since we want to load an operating system later on, we also need to be able to load more than one payload. Implementing ELFLOAD in each such plugin is inadequate. Instead LinuxBIOS should execute multiple payloads the same way it executes multiple "drivers" now.
* LinuxBIOS therefore needs a way to automatically determine payload
sizes when building the image and later when executing payloads.
Hardcoding the size values in the config files is inadequate and will
lead to unnecessary overhead
* LinuxBIOS at runtime needs to go through the list of available payloads, either by having a linked list of payload start points or by scanning the flash rom.
* LinuxBIOS should, to be consequent, remove all streaming code except CONFIG_ROM_STREAM
* Payloads should have the possibility to add their own enhancements to
the LinuxBIOS table.
* A least one payload should be "default payload" with the possibility to build this automatically and link it into the image.
This is why I checked the "util/extensions" directory into v2 during
the last discussion. It should hold possible choices to payloads that
can automatically be built and included. Potentially one could add
more payloads by symlinking their source tree to this directory to make
it available to LinuxBIOS without major reconfiguration.
People feel a lot safer with creating a symlink than with changing
config files they do not fully understand.
Since these can later be executed in row by elfboot, the minimum overhead design of LinuxBIOS itself will not be hurt.
At this point I want to put an idea to discussion: If we are going
more and more modular and some of us think the current tree is too
bloated: Why do we not modularize code like pci resource allocation
into a payload as well. My favorite bootloader may already do this
and I can't stand this bloat everywhere, you know ;) Even though this
may sound funny, I am serious about this issue. I do not see why
allocating PCI resources should really be part of the lowlevel code,
except for the fact that the NEXT payload in row, potentially Linux
itself is too stupid to do that. Bummer.
* LinuxBIOS configuration should have an easier mechanism for choosing payloads from the "default" directory, allowing them to be built automatically. Right now I am doing:
cd filo-0.4.2 linux32 make CC="gcc -m32" LD="ld -melf_i386" cd .. freebios2/targets/buildtarget amd/solo $PWD/freebios2 cd build-solo make cd .. cp build-solo/solo.rom .
My target Config.lb comes with these constructs: target ../../../../build-solo payload ../../filo-0.4.2/filo.elf
So I build everything completely out of the freebios2 tree, because building in-tree sucks. The only thing left is to get filo and the other payloads to build out-of-tree as well.
Comments? Discussion? Assassination attempts?
Stefan
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