[U-Boot] [RFC PATCH 1/3] add file with a default boot environment based heavily on Stephen Warrens recent tegra work.

[Tom Rini <trini@ti.com>]

On Wed, Feb 19, 2014 at 01:05:15PM -0600, Dan Murphy wrote:
> On 02/19/2014 01:02 PM, Eric Nelson wrote:
> > On 02/19/2014 11:57 AM, Stephen Warren wrote:
> >> On 02/19/2014 11:52 AM, Dan Murphy wrote:
> >>> On 02/19/2014 12:48 PM, Stephen Warren wrote:
> >>>> On 02/19/2014 11:44 AM, Dan Murphy wrote:
> >>>>> On 02/17/2014 11:56 AM, Dennis Gilmore wrote:
> >>>>>> Signed-off-by: Dennis Gilmore <dennis@ausil.us>
> >>>>>> diff --git a/include/config_distro_bootcmd.h b/include/config_distro_bootcmd.h
> >>>>>> +#ifdef CONFIG_CMD_USB
> >>>>>> +#define BOOTCMD_INIT_USB "run usb_init; "
> >>>>>> +#define BOOTCMDS_USB \
> >>>>>> +    "usb_init=" \
> >>>>>> +        "if ${usb_need_init}; then " \
> >>>>>> +            "set usb_need_init false; " \
> >>>>>> +            "usb start 0; " \
> >>>>>> +        "fi\0" \
> >>>>>> +    \
> >>>>>> +    "usb_boot=" \
> >>>>>> +        "setenv devtype usb; " \
> >>>>>> +        BOOTCMD_INIT_USB \
> >>>>>> +        "if usb dev ${devnum}; then " \
> >>>>> This may have already been highlighted but I don't see where the kernel command line arguments can be set.
> >>>>> If you have the file system on the USB stick won't you need to direct the root to the stick?
> >>>> They would be set in boot.scr or extlinux.cfg on the disk that the
> >>>> system boots from; the kernel cmdline is part of the OS that's installed
> >>>> there, not part of U-Boot. This is why these boot scripts load a
> >>>> script/config-file from the disk which in turn defines which
> >>>> kernel/DTB/cmdline to use, rather than directly loading a kernel and
> >>>> DTB. This approach should even be suitable for booting a non-Linux-OS,
> >>>> with suitable commands in boot.scr.
> >>>
> >>> But shouldn't the config file just be an override?
> >>>
> >>> I don't know if we should be having to need to load a boot.scr or any config file just to get the kernel to boot.
> >>>
> >>> If no config file exists should we not try to default to a known good default tested case?
> >>
> >> I believe always loading a script/config-file is the simplest and most
> >> flexible approach, for a *distro* *oriented* boot process.
> >
> > +1
> >
> > Scripts have the benefit of putting everything into a relatively
> > easy-to-read form that only uses documented U-Boot commands, not
> > board-specific constructs.
> >
> 
> Oh don't get me wrong I agree with having the scripts.
> 
> Just sayin we should not rely on the scripts being there and mandating
> their usage.
> We may want to have a fall back to a known good tested configuration.

I think I see where you're coming from, but it's already expected that
you're passing in a good device tree too, so it would be making sure
that you also have a useful env file to get loaded in the DHCP or PXE
case.

-- 
Tom
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