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;
> +}
> +
>  /*
>   * blspec_boot - boot an entry
>   *
> @@ -650,6 +673,10 @@ int blspec_boot(struct blspec_entry *entry, int verbose, int dryrun)
>  
>  	globalvar_add_simple("linux.bootargs.dyn.blspec", options);
>  
> +	ret = blspec_append_root(entry);
> +	if (ret)
> +		goto err_out;
> +
>  	pr_info("booting %s from %s\n", blspec_entry_var_get(entry, "title"),
>  			entry->cdev ? dev_name(entry->cdev->dev) : "none");
>  
> @@ -668,7 +695,7 @@ int blspec_boot(struct blspec_entry *entry, int verbose, int dryrun)
>  	ret = bootm_boot(&data);
>  	if (ret)
>  		pr_err("Booting failed\n");
> -
> +err_out:
>  	free((char *)data.oftree_file);
>  	free((char *)data.initrd_file);
>  	free((char *)data.os_file);
> 

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |