[U-Boot] [PATCH 1/3] config: introduce a generic $bootcmd

Jeroen Hofstee
2014-08-12T17:29:02Z

Hello Stephan,

On 11-08-14 20:55, Stephen Warren wrote:

<snip>

>>> No, Linux distros need to be able to install a single bootloader
>>> configuration file to tell the bootloader how to boot.
>>
>> Don't understand this, I though extlinux is yet another
>> chainloaded bootloader? I doubt there is "the bootloader".
>> I don't understand why it needs a single bootloader. It gets
>> in handy if the last bootloader is known, but I don't even see
>> why that is required.
>
> This is obviously where the disconnect is...
>
> extlinux is (IIRC) a bootloader yes. However, this patch isn't about
> extlinux, but extlinux.conf.
>

haha, right that is a funny misunderstanding. Yes, extlinux is
indeed a bootloader and I was in the impression you actively
searched for it to chainload it. And to make extlinux a requirement
for distro support... And as I tried to explain I am not that fond of
such an approach in general, and that had nothing to do, as Tom
suggested, with booting FreeBSD, it is just the image I encountered
searching for it in various places. It remains a badly named file
though (for U-boot), but well so be it, I guess.

> extlinux.conf is a text file format the defines a menu of bootable
> OSs. It's a (de-facto I suppose) standard that's implemented by
> extlinux (if indeed that is a piece of SW:-) and also U-Boot and
> barebox and likely other bootloaders too.
>
> So, when U-Boot locates extlinux.conf on disk and processes it, it's
> parsing a configuration file/menu, not chain-loading/executing another
> bootloader.
>

I see, so shouldn't we document then who is in charge of its format
at least, before we start making a U-boot/distro specific version of it?

<snip example file>
>
> That would require all Linux distros to have specific support to
> install boot.scr, which is a bootloader-specific format script file.
> Systems that boot using e.g. Barebox or other bootloaders presumably
> can't process boot.scr. However, if all bootloaders end up supporting
> extlinux.conf, the distro won't care what bootloader is on the HW.

We will see if this works, I am bit skeptical, but it is at least a
whole lot
better then polling all possible options, where I took the patch for. (Well
not all yet, but the start to do so).

Regards,
Jeroen