Re: [PATCH 6/6] blspec: Automatically append rootarg

[Sascha Hauer <s.hauer@pengutronix.de>]

On Tue, Jun 30, 2015 at 09:26:58AM +0200, Marc Kleine-Budde wrote:
> On 06/18/2015 09:43 AM, Sascha Hauer wrote:
> > This patch makes it possible to automatically add a suitable root= option
> > for booting Linux from the same filesystem on which the bootspec entry
> > has been found. This adds an additional 'linux-appendroot' option to
> > bootspec which if set to 'true' will cause barebox to automatically
> > add a root= option. This currently works for NFS, UBIFS and regular
> > block devices like ATA, SD/MMC using the root=PARTUUID= mechanism.
> > 
> > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> > ---
> >  Documentation/user/booting-linux.rst |  7 +++++++
> >  common/blspec.c                      | 29 ++++++++++++++++++++++++++++-
> >  2 files changed, 35 insertions(+), 1 deletion(-)
> > 
> > diff --git a/Documentation/user/booting-linux.rst b/Documentation/user/booting-linux.rst
> > index 6e7d155..39084e5 100644
> > --- a/Documentation/user/booting-linux.rst
> > +++ b/Documentation/user/booting-linux.rst
> > @@ -205,6 +205,13 @@ compatible NFS URI string must be passed to the boot command:
> >  
> >    boot nfs://nfshost//path/
> >  
> > +Additionally to the options defined in the original spec barebox understands the
> > +``linux-appendroot`` option. This is a boolean value and if set to ``true`` barebox
> > +will automatically append a ``root=`` string to the Linux commandline based on the
> > +device where the entry is found on. This makes it possible to use the same rootfs
> > +image on different devices without having to specify a different root= option each
> > +time.
> > +
> >  Network boot
> >  ------------
> >  
> > diff --git a/common/blspec.c b/common/blspec.c
> > index 3506388..742065e 100644
> > --- a/common/blspec.c
> > +++ b/common/blspec.c
> > @@ -601,6 +601,29 @@ int blspec_scan_devicename(struct blspec *blspec, const char *devname)
> >  	return blspec_scan_device(blspec, dev);
> >  }
> >  
> > +static int blspec_append_root(struct blspec_entry *entry)
> > +{
> > +	const char *appendroot;
> > +	char *rootarg;
> > +
> > +	appendroot = blspec_entry_var_get(entry, "linux-appendroot");
> > +	if (!appendroot || strcmp(appendroot, "true"))
> > +		return 0;
> > +
> 
> Can you move the following into a separate function outside of blspec.c
> so that it can be used somewhere else, too?
> 
> > +	rootarg = path_get_linux_rootarg(entry->rootpath);
> > +	if (IS_ERR(rootarg)) {
> > +		pr_err("Getting root argument for %s failed with: %s\n",
> > +				entry->rootpath, strerror(-PTR_ERR(rootarg)));
> > +		return PTR_ERR(rootarg);
> > +	}
> > +
> > +	globalvar_add_simple("linux.bootargs.dyn.blspec.appendroot", rootarg);
> > +
> > +	free(rootarg);
> > +
> > +	return 0;
> > +}

You mean the combination of path_get_linux_rootarg() and globalvar_add_simple()
should be a separate function? I'm not sure. Once we see a usecase for
this we can do this.

Hm, just thinking. We could create a barebox command which takes a
barebox device as argument and sets a linux.bootargs.* variable to the
corresponding root= snippet. This might be useful.

Sascha

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