[U-Boot] [RFC] fs: make it possible to read the filesystem UUID

Simon Glass sjg at chromium.org
Wed Oct 29 20:39:41 CET 2014


Hi Christian,

On 22 October 2014 07:29, Christian Gmeiner <christian.gmeiner at gmail.com> wrote:
> Some filesystems have a UUID stored in its superblock. To
> allow using root=UUID=... for the kernel command line we
> need a way to read-out the filesystem UUID. This is what this
> patch tries to do.
>
> Keep in mind that this patch is an RFC and I hope to get some
> feedback on this patch.
>
> This is what blkid under linux gives me:
> /dev/sdh1: LABEL="data" UUID="b6995cec-97e2-48b8-94dc-8ba7afc92bac" TYPE="ext4" PARTUUID="43f21f0e-01"
> /dev/sdh2: LABEL="rfs" UUID="8d020de7-c75e-4674-948e-f7838a931b02" TYPE="ext4" PARTUUID="43f21f0e-02"
>
> And here is the output from u-boot:
> => sata init
> AHCI 0001.0300 32 slots 1 ports 3 Gbps 0x1 impl SATA mode
> flags: ncq stag pm led clo only pmp pio slum part
> SATA Device Info:
> S/N: 000060059798A1000014
> Product model number: SFCA4096H1BR4TO-I-MS-236-STD
> Firmware version: 20111021
> Capacity: 7793856 sectors
> => fs_uuid sata 0:1 ; print fs_uuid; fs_uuid sata 0:2 ; print fs_uuid
> fs_uuid=b6995cec-97e2-48b8-94dc-8ba7afc92bac
> fs_uuid=8d020de7-c75e-4674-948e-f7838a931b02
>
> Signed-off-by: Christian Gmeiner <christian.gmeiner at gmail.com>
> ---
>  common/Makefile       |  1 +
>  common/cmd_fs_uuid.c  | 23 +++++++++++++++++++++++
>  fs/ext4/ext4_common.c |  9 +++++++++
>  fs/fs.c               | 28 ++++++++++++++++++++++++++++
>  include/ext4fs.h      |  1 +
>  include/fs.h          |  2 ++
>  6 files changed, 64 insertions(+)
>  create mode 100644 common/cmd_fs_uuid.c
>
> diff --git a/common/Makefile b/common/Makefile
> index b19d379..d5d3315 100644
> --- a/common/Makefile
> +++ b/common/Makefile
> @@ -188,6 +188,7 @@ obj-y += usb.o usb_hub.o
>  obj-$(CONFIG_USB_STORAGE) += usb_storage.o
>  endif
>  obj-$(CONFIG_CMD_FASTBOOT) += cmd_fastboot.o
> +obj-$(CONFIG_CMD_FS_UUID) += cmd_fs_uuid.o

Can this go in the cmd_fs file and be a subcommand? 'fs uuid' instead
of 'fs_uuid'.

>
>  obj-$(CONFIG_CMD_USB_MASS_STORAGE) += cmd_usb_mass_storage.o
>  obj-$(CONFIG_CMD_THOR_DOWNLOAD) += cmd_thordown.o
> diff --git a/common/cmd_fs_uuid.c b/common/cmd_fs_uuid.c
> new file mode 100644
> index 0000000..3af9518
> --- /dev/null
> +++ b/common/cmd_fs_uuid.c
> @@ -0,0 +1,23 @@
> +/*
> + * cmd_fs_uuid.c -- fs_uuid command
> + *
> + * Copyright (C) 2014, Bachmann electronic GmbH
> + *
> + * SPDX-License-Identifier:    GPL-2.0+
> + */
> +
> +#include <common.h>
> +#include <command.h>
> +#include <fs.h>
> +
> +static int do_fs_uuid_wrapper(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
> +{
> +       return do_fs_uuid(cmdtp, flag, argc, argv, FS_TYPE_ANY);
> +}
> +
> +U_BOOT_CMD(
> +       fs_uuid,        3,      0,      do_fs_uuid_wrapper,
> +       "filesystem UUDI related commands",
> +       "<interface> <dev>:<part>\n"
> +       "    - print filesystem UUID\n"
> +);
> diff --git a/fs/ext4/ext4_common.c b/fs/ext4/ext4_common.c
> index 33d69c9..926b6c6 100644
> --- a/fs/ext4/ext4_common.c
> +++ b/fs/ext4/ext4_common.c
> @@ -2246,3 +2246,12 @@ fail:
>
>         return 0;
>  }
> +
> +void ext4fs_uuid(char *uuid_str)
> +{
> +       if (ext4fs_root == NULL)
> +               return;
> +
> +       uuid_bin_to_str((unsigned char *)ext4fs_root->sblock.unique_id, uuid_str,
> +                       UUID_STR_FORMAT_STD);
> +}

I think this function should return 0 on success, and -ve on error (see errno.h)

> diff --git a/fs/fs.c b/fs/fs.c
> index dd680f3..f8c6d64 100644
> --- a/fs/fs.c
> +++ b/fs/fs.c
> @@ -85,6 +85,7 @@ struct fstype_info {
>         int (*size)(const char *filename);
>         int (*read)(const char *filename, void *buf, int offset, int len);
>         int (*write)(const char *filename, void *buf, int offset, int len);
> +       void (*uuid)(char *uuid_str);

Return error code. Also document the argument and return value. How
long should the string be?

>         void (*close)(void);
>  };
>
> @@ -113,6 +114,7 @@ static struct fstype_info fstypes[] = {
>                 .size = ext4fs_size,
>                 .read = ext4_read_file,
>                 .write = fs_write_unsupported,
> +               .uuid = ext4fs_uuid,
>         },
>  #endif
>  #ifdef CONFIG_SANDBOX
> @@ -206,6 +208,14 @@ static void fs_close(void)
>         fs_type = FS_TYPE_ANY;
>  }
>
> +void fs_uuid(char *uuid_str)
> +{
> +       struct fstype_info *info = fs_get_info(fs_type);
> +
> +       if (info->uuid)
> +               info->uuid(uuid_str);

Return error code

> +}
> +
>  int fs_ls(const char *dirname)
>  {
>         int ret;
> @@ -289,6 +299,24 @@ int fs_write(const char *filename, ulong addr, int offset, int len)
>         return ret;
>  }
>
> +int do_fs_uuid(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[],
> +               int fstype)
> +{
> +       char uuid[37];
> +       memset(uuid, 0, sizeof(uuid));
> +
> +       if (argc != 3)
> +               return CMD_RET_USAGE;
> +
> +       if (fs_set_blk_dev(argv[1], argv[2], fstype))
> +               return 1;
> +
> +       fs_uuid(uuid);

Check error code

> +       setenv("fs_uuid", uuid);

How about making the environment variable an option parameter. If not
given, the UUID is printed out. If given, it is stored in the env
variable.

> +
> +       return 0;
> +}
> +
>  int do_size(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[],
>                 int fstype)
>  {
> diff --git a/include/ext4fs.h b/include/ext4fs.h
> index 6c419f3..4011370 100644
> --- a/include/ext4fs.h
> +++ b/include/ext4fs.h
> @@ -132,6 +132,7 @@ struct ext_filesystem *get_fs(void);
>  int ext4fs_open(const char *filename);
>  int ext4fs_read(char *buf, unsigned len);
>  int ext4fs_mount(unsigned part_length);
> +void ext4fs_uuid(char *uuid_str);
>  void ext4fs_close(void);
>  void ext4fs_reinit_global(void);
>  int ext4fs_ls(const char *dirname);
> diff --git a/include/fs.h b/include/fs.h
> index 06a45f2..1956b67 100644
> --- a/include/fs.h
> +++ b/include/fs.h
> @@ -82,6 +82,8 @@ int fs_write(const char *filename, ulong addr, int offset, int len);
>   * Common implementation for various filesystem commands, optionally limited
>   * to a specific filesystem type via the fstype parameter.
>   */
> +int do_fs_uuid(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[],
> +               int fstype);
>  int do_size(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[],
>                 int fstype);
>  int do_load(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[],

BTW you can use patman (tools/patman/patman) which will run
get_maintainer.pl for you and send your patch, and deal with change
list, etc.

Regards,
Simon


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