[PATCH] USB: gadget: fastboot: introduce optional flag for fastboot partitions

[Ahmad Fatoum]

Hi,

On 22.09.22 08:27, Johannes Zink wrote:
> On some boards, some partitions exposed to fastboot may become
> unavailable under certain circumstances, e.g. if an SD-Card exposed to
> fastboot is removed.
> 
> Previously, this lead to an error and the fastboot gadget did not
> initialize the remaining partitions exposed via fastboot, e.g. an
> eMMC which usually is permanently soldered on the board.
> 
> This patch allows to append an optional flag 'o' to the description of a
> fastboot partition. If this partition is unavailable at the
> initialization of the fastboot gadget, said partition is skipped, while
> the remaining available partitions are still exposed.
> 
> Signed-off-by: Johannes Zink <j.zink at pengutronix.de>
> ---
>  Documentation/user/usb.rst | 1 +
>  common/fastboot.c          | 6 +++++-
>  common/file-list.c         | 3 +++
>  include/file-list.h        | 1 +
>  4 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/user/usb.rst b/Documentation/user/usb.rst
> index 2479efe9d6..f2f57ead98 100644
> --- a/Documentation/user/usb.rst
> +++ b/Documentation/user/usb.rst
> @@ -65,6 +65,7 @@ Several **flags** are supported, each denoted by a single character:
>  * ``r`` Readback. The partition is allowed to be read back (DFU specific)
>  * ``c`` The file shall be created if it doesn't exist. Needed when a regular file is exported.
>  * ``u`` The partition is a MTD device and shall be flashed with a UBI image.
> +* ``o`` The partition is optional, i.e. if it is not available at initialization time, it is skipped instead of aborting the initialization
>  
>  Example:
>  
> diff --git a/common/fastboot.c b/common/fastboot.c
> index 330a06f5a3..6bd1191325 100644
> --- a/common/fastboot.c
> +++ b/common/fastboot.c
> @@ -177,7 +177,11 @@ int fastboot_generic_init(struct fastboot *fb, bool export_bbu)
>  	file_list_for_each_entry(fb->files, fentry) {
>  		ret = fastboot_add_partition_variables(fb, fentry);
>  		if (ret)
> -			return ret;
> +			if((fentry->flags & FILE_LIST_FLAG_OPTIONAL))
> +				pr_info("failed to add optional partition %s to fastboot gadget\n",

s/failed to add/skipping unavailable/

to make this more in line with the chosen log level.

> +					fentry->filename);
> +			else
> +				return ret;

Please avoid dangling else here, either with braces or by having an 
if (ret && fentry->flags & FILE_LIST_FLAG_OPTIONAL)) as first condition.

>  	}
>  
>  	return 0;
> diff --git a/common/file-list.c b/common/file-list.c
> index 407b312833..68a7768696 100644
> --- a/common/file-list.c
> +++ b/common/file-list.c
> @@ -88,6 +88,9 @@ static int file_list_parse_one(struct file_list *files, const char *partstr, con
>  			case 'u':
>  				flags |= FILE_LIST_FLAG_UBI;
>  				break;
> +			case 'o':
> +				flags |= FILE_LIST_FLAG_OPTIONAL;
> +				break;
>  			default:
>  				pr_err("Unknown flag '%c'\n", *partstr);
>  				return -EINVAL;

When adding new flags, search for all instances of a similar flag and add
your new flag there as well. You're missing flags_to_str().

> diff --git a/include/file-list.h b/include/file-list.h
> index 5090313739..bcb06979c8 100644
> --- a/include/file-list.h
> +++ b/include/file-list.h
> @@ -8,6 +8,7 @@
>  #define FILE_LIST_FLAG_READBACK	(1 << 1)
>  #define FILE_LIST_FLAG_CREATE	(1 << 2)
>  #define FILE_LIST_FLAG_UBI	(1 << 3)
> +#define FILE_LIST_FLAG_OPTIONAL (1 << 4)
>  
>  struct file_list_entry {
>  	char *name;

Cheers,

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |