[U-Boot] [PATCH v2 3/4] ubifs: Add generic fs support

[Stephen Warren <swarren@wwwdotorg.org>]

On 08/22/2015 11:04 AM, Hans de Goede wrote:
> Add generic fs support, so that commands like ls, load and test -e can be
> used on ubifs.

> @@ -530,6 +531,28 @@ int get_device_and_partition(const char *ifname, const char *dev_part_str,
>  		return 0;
>  	}
>  
> +#ifdef CONFIG_CMD_UBIFS
> +	/*
> +	 * Special-case ubi, ubi goes through a mtd, rathen then through
> +	 * a regular block device.
> +	 */
> +	if (0 == strcmp(ifname, "ubi")) {
> +		if (!ubifs_mounted) {
> +			printf("UBIFS not mounted, use ubifsmount to mount volume first!\n");
> +			return -1;
> +		}
> +
> +		*dev_desc = NULL;
> +		memset(info, 0, sizeof(*info));
> +		strcpy((char *)info->type, BOOT_PART_TYPE);
> +		strcpy((char *)info->name, "UBI");
> +#ifdef CONFIG_PARTITION_UUIDS
> +		info->uuid[0] = 0;
> +#endif
> +		return 0;
> +	}
> +#endif

We now have two paths through this function that can "Return" a NULL
dev_desc. This makes it impossible for sandbox and ubifs to successfully
co-exist in the same U-Boot binary, since the sandbox and ubifs fs probe
functions won't be able to tell if "hostfs" or "ubifs" was passed to
get_device_and_partition(). Perhaps there's no ubifs support in sandbox
right now, so there's no issue?

If this is an issue that needs to be solved now, I think the best
solution would be for the two special cases in
get_device_and_partition() to "return" a real dev_desc rather than NULL.
Since there's nothing meaningful to put there, how about returning a
hard-coded value that can then be checked in the fs probe functions to
make sure it matches:

get_device_and_partition():

	if (hostfs) {
		...
		*dev_desc = &hostfs_fake_dev_desc;
		...
		return 0;
	}
	if (ubi) {
		...
		*dev_desc = &ubifs_fake_dev_desc;
		...
		return 0;
	}

ubifs_set_blk_dev():

	if (rbdd != &ubifs_fake_dev_desc)
		return -1;
	...
	return 0;

... that said, I wonder if the ubifs special case in
get_device_and_partition() shouldn't actually perform the ubifs_mount()
call itself, based on the user-supplied parameters?