[Arm-netbook] CONFIG_CMDLINE, override uboot parameters

[Liviu Dudau]

Hi Peter,

The 4th option that you want doesn't exist.

Thing is, if you want to overwrite some of u-boot options then the following
two things are true:

  a. you know the u-boot parameters
  b. you know one (or many) of them are wrong

Most people in that case use option 2) and overwrite the bootloader command
line with the one they want. If you are worried about someone going into
u-boot and adding another useful command line parameter that you might be
missing if you use option 2) then you need to explain to them what they
also need to correct in that command line that is currently broken.

Best regards,
Liviu


On Wed, Feb 20, 2013 at 10:17:31AM +0100, Peter Steenbergen wrote:
> Thanks Piyush,
> 
> I know about the uboot saved parameters. The whole point is that I do not
> want to touch the by the factory flashed uboot. There are now three
> CONFIG_CMDLINE options
> 1) CONFIG_CMDLINE_BOOTLOADER == Always use the ones passed by the bootloader
> 2 CONFIG_CMDLINE_FORCE == Always use the under CMDLINE defined parameters,
> ignore the ones passed by the bootloader
> 3) CONFIG_EXTEND == Insert parameters and APPEND the ones passed by the
> bootloader. This is designed such, that you can define missing parameters
> not defined by the bootloader.
> 
> With the latter, if you define a parameter which is also passed by the
> bootloader, the by CMDLINE configured one wil be overwritten by the one
> passed from the bootloader. This is simply because the function to fill for
> instance the rootfstype parameter is called twice.
> 
> What I am basically are looking for is a fourth config option,
> CONFIG_CMDLINE_OVERRIDE, where the by the bootloader passed parameters are
> being appended by the ones defined in the CMDLINE. It is basically the
> EXTEND, but then the other way around. It still EXTENDS the ones not
> defined by the bootloader, but if you define a parameter in the kernel
> which is also set by the CMDLINE the ones from the bootloader are
> overwritten by the ones defined in the kernel.
> 
> At this moment, a quick hack has been applied to set a boolean for the
> rootfstype one;
> https://github.com/j1nx/buildroot-linux-kernel-m3/commit/52476f9f911ee9c08acda0976331aa5465ff16a7
> But a fourth CONFIG parameter will solve the same issue for any other
> possible parameters. The thing is; I can't believe I am the only one that
> wants to override uboot parameters. It might be already out there...
> 
> Cheers
> 
> 
> On Wed, Feb 20, 2013 at 3:32 AM, Piyush Verma <piyush.pv at gmail.com> wrote:
> 
> > While booting we can stop at uboot prompt.
> >
> > there we can see all environment variable with printenv.
> > we can change it by setenv. don't forget to save it by saveenv after
> > changing environment variable.
> >
> > bootargs is the environment variable where we can pass all rootfs details.
> >
> > Does it solve ur issue ?
> >
> > On Wed, Feb 20, 2013 at 4:01 AM, Peter Steenbergen <p.steenbergen at j1nx.nl>wrote:
> >
> >> I am running into an issue with my Amlogic XBMC development. Before I go
> >> out searching the dark secrets of the linux kernel, I thought why not ask
> >> you guys first.
> >>
> >> There is this patch;
> >>
> >> http://lists.infradead.org/pipermail/linux-arm-kernel/2011-April/047506.html
> >> Which is used often. It adds the CONFIG_CMDLINE_EXTEND to the possible
> >> CMDLINE options. It is designed to prepend the cmdline parameters in case
> >> there are missing values. The passed parameters by uboot are then appended
> >> to the ones from CONFIG_CMDLINE.
> >>
> >> This all works fine if you indeed are missing parameters, but what if i
> >> want to overwrite/override an already by uboot passed parameter? (like
> >> root= and rootfstype=)
> >>
> >> I don't want to FORCE everything, because I then have to take over the
> >> complete line as passed by uboot. If I do that I will loose the parameters
> >> set by variables within uboot (MAC)
> >>
> >> If I set them in CMDLINE, then the ones passed from uboot are appended
> >> and overriding the ones from CMDLINE.
> >>
> >> I also do not want to change uboot as that is still kind of tricky on the
> >> Amlogic boxes.
> >>
> >> Do anyone of you guys have some tips and/or directions?
> >>
> >> thanks
> >>
> >> _______________________________________________
> >> arm-netbook mailing list arm-netbook at lists.phcomp.co.uk
> >> http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook
> >> Send large attachments to arm-netbook at files.phcomp.co.uk
> >>
> >
> >
> >
> > --
> > Thanks & Regards
> >
> > Piyush Verma
> >
> >
> > _______________________________________________
> > arm-netbook mailing list arm-netbook at lists.phcomp.co.uk
> > http://lists.phcomp.co.uk/mailman/listinfo/arm-netbook
> > Send large attachments to arm-netbook at files.phcomp.co.uk
> >

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