[PATCH V2 3/4] mtd: partitions: add of_match_table parser matching

[Jonas Gorski]

Hi,

On 24 April 2017 at 14:41, Rafał Miłecki <zajec5 at gmail.com> wrote:
> From: Brian Norris <computersforpeace at gmail.com>
>
> Partition parsers can now provide an of_match_table to enable
> flash<-->parser matching via device tree.
>
> This support is currently limited to built-in parsers as it uses
> request_module() and friends. This should be sufficient for most cases
> though as compiling parsers as modules isn't a common choice.
>
> Signed-off-by: Brian Norris <computersforpeace at gmail.com>
> Signed-off-by: Rafał Miłecki <rafal at milecki.pl>
> Acked-by: Brian Norris <computersforpeac at gmail.com>
> ---
> This is based on Brian's patches:
> [RFC PATCH 4/7] mtd: add of_match_mtd_parser() and of_mtd_match_mtd_parser() helpers
> [RFC PATCH 6/7] RFC: mtd: partitions: enable of_match_table matching
>
> V1: Put helpers in mtdpart.c instead of drivers/of/of_mtd.c
>     Merge helpers into a single of_mtd_match_mtd_parser
> ---
>  drivers/mtd/mtdpart.c          | 47 ++++++++++++++++++++++++++++++++++++++++++
>  include/linux/mtd/partitions.h |  1 +
>  2 files changed, 48 insertions(+)
>
> diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
> index 73c52f1a2e4c..d0cb1a892ed2 100644
> --- a/drivers/mtd/mtdpart.c
> +++ b/drivers/mtd/mtdpart.c
> @@ -861,6 +861,41 @@ static int mtd_part_do_parse(struct mtd_part_parser *parser,
>         return ret;
>  }
>
> +static bool of_mtd_match_mtd_parser(struct mtd_info *mtd,
> +                                   struct mtd_part_parser *parser)
> +{
> +       struct device_node *np;
> +       bool ret;
> +
> +       np = mtd_get_of_node(mtd);
> +       np = of_get_child_by_name(np, "partitions");
> +
> +       ret = !!of_match_node(parser->of_match_table, np);
> +
> +       of_node_put(np);
> +
> +       return ret;
> +}
> +
> +static struct mtd_part_parser *mtd_part_get_parser_by_of(struct mtd_info *mtd)
> +{
> +       struct mtd_part_parser *p, *ret = NULL;
> +
> +       spin_lock(&part_parser_lock);
> +
> +       list_for_each_entry(p, &part_parsers, list) {
> +               if (of_mtd_match_mtd_parser(mtd, p) &&
> +                               try_module_get(p->owner)) {
> +                       ret = p;
> +                       break;
> +               }
> +       }


Hm, maybe iterate over the compatibles, so parsers matching the most
specific compatible get precedence in case there is more than one
compatible? Currently it will match the first one that matches any
compatible, and registration order of parsers can change that. I'm
thinking of parsers that partially rely on fixed, unprobable layouts,
so can use "fixed-partitions" as a fallback compatible.

E.g. having something like this

partitions {
        compatible = "sample,custom-layout", "fixed-partitions";

        bootloader at 0 { ...  };

        firmware at 10000 { .... }; /* will be split by the parser */

        extra at 780000 { .... }; /* partition the on-flash format can't specify */
};

Where you will still be able to write an image raw to the image
partition even if the "custom-layout"-parser isn't present/enabled,
but if it is present, it should always be used.


Regards
Jonas