[PATCH 3/3] state: support backend-diskuuid / backend-offset

[Sascha Hauer]

On Mon, Jan 24, 2022 at 11:04:58AM +0100, Michael Olbrich wrote:
> On some platforms (e.g. EFI on x86_64) the state backend can only be
> selected by a partiton UUID. On existing devices with a DOS partition
> table, there may be no spare partition available for state.
> 
> This makes it possible to select the disk via UUID. The exact position is
> defined by an explicitly specified offset.
> 
> Signed-off-by: Michael Olbrich <m.olbrich at pengutronix.de>
> ---
> 
> I wasn't sure where to add the helper function. Is include/fs.h ok or
> should I put it somewhere else?
> 
> I'll implement the same helper for dt-utils, so we can avoid additional
> #ifdef here.
> 
>  common/state/state.c | 55 +++++++++++++++++++++++++++++---------------
>  include/fs.h         | 12 ++++++++++
>  2 files changed, 49 insertions(+), 18 deletions(-)
> 
> diff --git a/common/state/state.c b/common/state/state.c
> index 8c34ae83e52b..2a8b12d20c5a 100644
> --- a/common/state/state.c
> +++ b/common/state/state.c
> @@ -592,6 +592,7 @@ struct state *state_new_from_node(struct device_node *node, bool readonly)
>  	const char *backend_type;
>  	const char *storage_type = NULL;
>  	const char *alias;
> +	const char *diskuuid;
>  	uint32_t stridesize;
>  	struct device_node *partition_node;
>  	off_t offset = 0;
> @@ -607,30 +608,48 @@ struct state *state_new_from_node(struct device_node *node, bool readonly)
>  	if (IS_ERR(state))
>  		return state;
>  
> -	partition_node = of_parse_phandle(node, "backend", 0);
> -	if (!partition_node) {
> -		dev_err(&state->dev, "Cannot resolve \"backend\" phandle\n");
> -		ret = -EINVAL;
> -		goto out_release_state;
> -	}
> +	ret = of_property_read_string(node, "backend-diskuuid", &diskuuid);

This needs some documentation in
Documentation/devicetree/bindings/barebox/barebox,state.rst.

> +	if (ret == 0) {
> +		u64 off;
> +
> +		ret = devpath_from_diskuuid(diskuuid, &state->backend_path);
> +		if (ret) {
> +			dev_err(&state->dev, "state failed find backend device for diskuuid='%s'\n",
> +				diskuuid);
> +			goto out_release_state;
> +		}
> +		ret = of_property_read_u64(node, "backend-offset", &off);

I stumbled upon this because you have to use a 64bit type here instead
of using 'offset' directly. I think 'offset' should be 64bit instead so
that larger offsets can be used.

> +		if (ret) {
> +			dev_err(&state->dev, "'backend-offset' property undefined\n");
> +			goto out_release_state;
> +		}
> +		offset = off;

What about the size of the state partition? This is not set anywhere in
this case so it's still zero. It should be specified the in device tree
as well. At the same time I'm a bit nervous that it apparently still
works with size zero.

Sascha

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