Re: [PATCH V4 2/3] mtd: add core code reading DT specified part probes

[Boris Brezillon <boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>]

On Mon, 17 Apr 2017 20:28:52 +0200
Rafał Miłecki <zajec5-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> From: Rafał Miłecki <rafal-g1n6cQUeyibVItvQsEIGlw@public.gmane.org>
> 
> Handling (creating) partitions for flash devices requires using a proper
> driver that will read partition table (out of somewhere). We can't
> simply try all existing drivers one by one:
> 1) It would increase boot time
> 2) The order could be a problem
> 3) In some corner cases parsers could misinterpret some data as a table
> Due to this MTD subsystem allows drivers to specify a list of applicable
> part probes.
> 
> So far physmap_of was the only driver with support for linux,part-probe
> DT property. Other ones had list or probes hardcoded which wasn't making
> them really flexible. It prevented using common flash drivers on
> platforms that required some specific partition table access.
> 
> This commit adds support for mentioned DT property directly to the MTD
> core. It's a rewritten implementation of physmap_of's code and it makes
> original code obsolete. Thanks to calling it on device parse
> registration (as suggested by Boris) all drivers gain support for it for
> free.
> 
> Signed-off-by: Rafał Miłecki <rafal-g1n6cQUeyibVItvQsEIGlw@public.gmane.org>
> ---
> V4: Rename of functions
>     Add comment to the of_get_mtd_part_probes
>     Simplify mtd_device_parse_register changes
>     Thanks Boris for help on all above!
> ---
>  drivers/mtd/mtdcore.c | 34 ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> index 66a9dedd1062..07b07de7e080 100644
> --- a/drivers/mtd/mtdcore.c
> +++ b/drivers/mtd/mtdcore.c
> @@ -664,6 +664,33 @@ static void mtd_set_dev_defaults(struct mtd_info *mtd)
>  	}
>  }
>  
> +static const char * const *of_get_mtd_part_probes(struct device_node *np)
> +{
> +	const char **res;
> +	int count;
> +
> +	count = of_property_count_strings(np, "linux,part-probe");
> +	if (count < 0)
> +		return NULL;
> +
> +	/* This looks common: consider helper function if copying */
> +	res = kzalloc((count + 1) * sizeof(*res), GFP_KERNEL);
> +	if (!res)
> +		return NULL;
> +
> +	count = of_property_read_string_array(np, "linux,part-probe", res,
> +					      count);
> +	if (count < 0)
> +		return NULL;
> +
> +	return res;
> +}
> +
> +static void of_free_mtd_part_probes(const char * const *probes)
> +{
> +	kfree(probes);
> +}
> +
>  /**
>   * mtd_device_parse_register - parse partitions and register an MTD device.
>   *
> @@ -698,11 +725,16 @@ int mtd_device_parse_register(struct mtd_info *mtd, const char * const *types,
>  			      const struct mtd_partition *parts,
>  			      int nr_parts)
>  {
> +	const char * const *part_probe_types;

One last thing: can we rename this variable of_part_probe_types?

With this addressed,

Acked-by: Boris Brezillon <boris.brezillon-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>

Thanks,

Boris

>  	struct mtd_partitions parsed;
>  	int ret;
>  
>  	mtd_set_dev_defaults(mtd);
>  
> +	part_probe_types = of_get_mtd_part_probes(mtd_get_of_node(mtd));
> +	if (part_probe_types)
> +		types = part_probe_types;
> +
>  	memset(&parsed, 0, sizeof(parsed));
>  
>  	ret = parse_mtd_partitions(mtd, types, &parsed, parser_data);
> @@ -720,6 +752,8 @@ int mtd_device_parse_register(struct mtd_info *mtd, const char * const *types,
>  		memset(&parsed, 0, sizeof(parsed));
>  	}
>  
> +	of_free_mtd_part_probes(part_probe_types);
> +
>  	ret = mtd_add_device_partitions(mtd, &parsed);
>  	if (ret)
>  		goto out;

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