Hello Marco,
On 06.05.21 13:22, Marco Felsch wrote:
> Since commit fa2d0aa96941 ("mmc: core: Allow setting slot index via
> device tree alias") the kernel supports stable mmc device names. Since
> the barebox mmc device names matches the one from the kernel we can pass
> the 'root=mmcblkXpN' argument on commandline to refer to the correct
> boot medium.
>
> This patch adds the support to store the above commandline as
> linux_rootarg if enabled. Use the partuuid as fallback since it is not
> as unique as the mmcblkXpN scheme. Add a own build option since the
> system integrator needs to check if the used kernel contains the above
> commit.
>
> Signed-off-by: Marco Felsch <m.felsch@xxxxxxxxxxxxxx>
> ---
> Hi all,
>
> I know that:
> 8<-----------------
> + if (!str && fsdev->cdev->partuuid[0] != 0)
> + str = basprintf("root=PARTUUID=%s", fsdev->cdev->partuuid);
> 8<-----------------
> is longer than 80char but for the sake of readability I kept that
> oneliner. Should we update checkpatch accordingly to match the new linux
> rule?
Yes, I already adhere to the new Linux convention in my barebox code.
>
> Regards,
> Marco
>
>
> common/Kconfig | 15 +++++++++++++++
> fs/fs.c | 48 ++++++++++++++++++++++++++++++++++++++++++++----
> 2 files changed, 59 insertions(+), 4 deletions(-)
>
> diff --git a/common/Kconfig b/common/Kconfig
> index 6b3c1701be..a09a1d9456 100644
> --- a/common/Kconfig
> +++ b/common/Kconfig
> @@ -700,6 +700,21 @@ config FLEXIBLE_BOOTARGS
> to replace parts of the bootargs string without reconstructing it
> completely.
>
> +config MMCBLKDEV_ROOTARG
> + bool
> + prompt "Support 'root=mmcblkXpN' cmdline appending"
> + help
> + Enable this option to append 'root=mmcblkXpN' to the kernel cmdline
> + instead of 'root=PARTUUID=XYZ'. Don't enale this option if your used
> + kernel don't contain commit [1].
Could you add the first mainline Linux release that includes the commit?
> +
> + The appending only happen if barebox 'linux.bootargs.bootm.appendroot'
> + variable is set or the used blspec entry contains 'linux-appendroot'.
> +
> + [1] fa2d0aa96941 ("mmc: core: Allow setting slot index via device tree
> + alias")
> +
> +
> config BAREBOX_UPDATE
> bool "In-system barebox update infrastructure"
>
> diff --git a/fs/fs.c b/fs/fs.c
> index 881dc2fca0..8ee1e7febe 100644
> --- a/fs/fs.c
> +++ b/fs/fs.c
> @@ -2831,6 +2831,39 @@ out:
> }
> EXPORT_SYMBOL(chdir);
>
> +static char *get_linux_mmcblkdev(struct fs_device_d *fsdev)
> +{
> + struct cdev *cdevm, *cdev;
> + int id, partnum;
> + bool found = false;
> +
> + cdevm = fsdev->cdev->master;
> + id = of_alias_get_id(cdevm->device_node, "mmc");
> + if (id < 0)
> + return NULL;
> +
> + partnum = 1; /* linux partitions are 1 based */
> + list_for_each_entry(cdev, &cdevm->partitions, partition_entry) {
> +
> + /*
> + * Partname is not guaranteed but this partition cdev is listed
> + * in the partitions list so we need to count it instead of
> + * skipping it.
> + */
> + if (cdev->partname &&
> + !strcmp(cdev->partname, fsdev->cdev->partname)) {
> + found = true;
You can return the basprintf() here directly
> + break;
> + }
> + partnum++;
> + }
> +
> + if (!found)
> + return NULL;
> +
> + return basprintf("root=/dev/mmcblk%dp%d", id, partnum);
Then you can return NULL here and drop found.
> +}
> +
> /*
> * Mount a device to a directory.
> * We do this by registering a new device on which the filesystem
> @@ -2919,11 +2952,18 @@ int mount(const char *device, const char *fsname, const char *pathname,
>
> fsdev->vfsmount.mnt_root = fsdev->sb.s_root;
>
> - if (!fsdev->linux_rootarg && fsdev->cdev && fsdev->cdev->partuuid[0] != 0) {
> - char *str = basprintf("root=PARTUUID=%s",
> - fsdev->cdev->partuuid);
> + if (!fsdev->linux_rootarg && fsdev->cdev) {
> + char *str = NULL;
> +
> + if (IS_ENABLED(CONFIG_MMCBLKDEV_ROOTARG) &&
> + cdev_is_mci_dev(fsdev->cdev->master))
> + str = get_linux_mmcblkdev(fsdev);
> +
> + if (!str && fsdev->cdev->partuuid[0] != 0)
> + str = basprintf("root=PARTUUID=%s", fsdev->cdev->partuuid);
>
> - fsdev_set_linux_rootarg(fsdev, str);
> + if (str)
> + fsdev_set_linux_rootarg(fsdev, str);
This assumes that barebox aliases align with those of the kernel. I think this
is at least worth a mention in the Kconfig text.
For an alternative, see f382be77f8c0 ("boot: introduce option to pass
barebox-enabled watchdog to systemd"), which parses the aliases out of the
kernel device tree without depending on the barebox ones.
Cheers,
Ahmad
> }
>
> path_put(&path);
>
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