On Fri, Jan 21, 2022 at 08:20:17AM -0700, Simon Glass wrote:
Hi,
On Fri, 21 Jan 2022 at 08:08, Tom Rini trini@konsulko.com wrote:
On Wed, Jan 19, 2022 at 12:39:03PM +0100, Heinrich Schuchardt wrote:
On 1/19/22 02:43, Simon Glass wrote:
[snip]
+Introduction +------------
+Standard boot provides a built-in way for U-Boot to automatically boot +an Operating System without custom scripting and other customisation. It +introduces the following concepts:
- bootdev - a device which can hold or access a distro (e.g. MMC, Ethernet)
- bootmeth - a method to scan a bootdev to find bootflows (e.g. distro boot)
- bootflow - a description of how to boot (provided by the distro)
+For Linux, the distro (Linux distribution, e.g. Debian, Fedora) is responsible +for creating a bootflow for each kernel combination that it wants to offer.
This gets it completely wrong. There is one standardized boot flow: UEFI. All major distros support this. U-Boot has to offer UEFI booting out of the box.
I want to jump up and down and emphasize this part as well. While I believe our UEFI bootmgr is still missing the normal scan code, that's something that has been promised to be implemented. And that turns the bootcmd for platforms that just want to support modern off the shelf distros in to something fairly small.
Sigh...
UEFI is a bootflow in this model, one of many. If we don't support the others, then U-Boot is not U-Boot anymore, it is just EFI Boot.
No one is talking about removing anything else. But a major part of your motivation here seems to be "discovering what to boot where is a pain" and that's solved (or at least defined, I'm poking Ilias about the status of that off-list). And I want to emphasize discover.
If we get EFI bootmgr going, then are you saying you want to disable everything else?
Not at all.
You say 'major distros' but there are many that don't use it, particularly in the embedded space. I'll go out on a limb and say that the vast majority of embedded devices in the world don't use it. Are you really saying we should drop support for everything else? Even the distro stuff supports other options.
I don't know about buildroot off-hand, but I've had OpenEmbedded spit out UEFI-compatible aarch64 images no problem. If you're talking about embedded Debian/Ubuntu/Fedora, that goes back up to "wants UEFI boot flow". Armbian is the biggest distro I know of off-hand that doesn't do UEFI boot for U-Boot targets and I would love to talk with someone there and find out why (but I guess it's all the 32bit platforms).
But I'd also say the vast majority of embedded devices don't need the complexity you're adding here, but DO need the ability to implement A/B things as easily in U-Boot as they can in grub. And that in turn is because it's a pain to modify the default environment in U-Boot and easy to drop in another script for grub.