[U-Boot] [PATCH 2/2] config_distro_defaults.h: add CONFIG_API

[Jeroen Hofstee <jeroen@myspectrum.nl>]

Hello Tom,

On 23-08-14 19:47, Tom Rini wrote:
> On Sun, Aug 10, 2014 at 12:30:56AM +0200, Jeroen Hofstee wrote:
>
>> Grub, FreeBSD ubldr, vxworks etc depend on the API
>>
>> Signed-off-by: Jeroen Hofstee <jeroen@myspectrum.nl>

ok, lets start with I hope what I hope config_distro_defaults is.
At the moment, if you buy a demo board and try to run a custom
image on it, chances are big it won't boot. Either because it
searches for a wrong file, commands are not supported, they have
different syntax, different image formats etc. It is not uncommon
that I need to update u-boot before I can run a simple custom image.
It would of course be a lot better if you can stick an image in a demo
board, which actually boots and even better optionally ask you what
to boot. And I am in the impression / hope config_distro_defaults is
for that purpose. Not the smallest / fastest u-boot, but one which can
actually boot different distro's, images, demos etc. (or at least an
attempt to do so). For completeness, this already holds for linux
distro's / images / buildtools.

The typical bootpath for FreeBSD images is:

[something] -> loader[1] -> FreeBSD

In case of u-boot "something" is u-boot and loader is ubldr (which is
loader to talk with u-boot by its API). It would be nice if this just
worked without modifying u-boot, as the image might be in nand etc.

> So I'm not 100% sold on this.  A while back (it's in the archives) we
> had said no to CONFIG_API. Grub wasn't a good use-case

I couldn't find a good reason why grub is not an use-case.
(besides some complaining and no-funding)

> (esp since we're handling extlinux.conf files),

I am still in the dark with respect to extlinux.conf. There is no
documentation nor users for it in u-boot it seems. But even if
an FreeBSD boot would use a FreeBSD.conf or similiar it would
still need CONFIG_API to work correctly.


> VxWorks is bootm/bootelf.
grep said:

/* Boot FreeBSD/vxWorks from an ELF image */
#if defined(CONFIG_ZYNQ_BOOT_FREEBSD)
# define CONFIG_API
# define CONFIG_CMD_ELF
# define CONFIG_SYS_MMC_MAX_DEVICE      1
#endif

hence I assumed it needs the api as well.

>
> I am open to hearing how/why we need this for ubldr.
>

ublr depends on a u-boot with CONFIG_API enabled. It
won't work otherwise.

[2] contains some background about the boot process from
u-boot.

Regards,
Jeroen

[1] https://www.freebsd.org/cgi/man.cgi?loader(8)
[2] 
http://www.bsdcan.org/2008/schedule/attachments/49_2008_uboot_freebsd.pdf