[U-Boot] [PATCH 1/4] dm: core: Add of_alias_get_highest_id()

[Simon Glass]

Hi Michal,

On Fri, 18 Jan 2019 at 08:13, Michal Simek <michal.simek at xilinx.com> wrote:
>
> The same functionality was added to Linux for i2c bus registration with this
> commit message:
>
> "
> of: base: add function to get highest id of an alias stem
>
> I2C supports adding adapters using either a dynamic or fixed id. The
> latter is provided by aliases in the DT case. To prevent id collisions
> of those two types, install this function which gives us the highest
> fixed id, so we can then let the dynamically created ones come after
> this highest number.
>
> Signed-off-by: Wolfram Sang <wsa+renesas at sang-engineering.com>
> Acked-by: Rob Herring <robh at kernel.org>
> Signed-off-by: Wolfram Sang <wsa at the-dreams.de>
> "
>
> Add it also to U-Boot for DM I2C support.
>
> Signed-off-by: Michal Simek <michal.simek at xilinx.com>
> ---
>
>  drivers/core/of_access.c | 18 ++++++++++++++++++
>  include/dm/of_access.h   |  9 +++++++++
>  2 files changed, 27 insertions(+)
>
> diff --git a/drivers/core/of_access.c b/drivers/core/of_access.c
> index 14c020a687b7..7c2df2354109 100644
> --- a/drivers/core/of_access.c
> +++ b/drivers/core/of_access.c
> @@ -812,6 +812,24 @@ int of_alias_get_id(const struct device_node *np, const char *stem)
>         return id;
>  }
>
> +int of_alias_get_highest_id(const char *stem)
> +{
> +       struct alias_prop *app;
> +       int id = -ENODEV;
> +
> +       mutex_lock(&of_mutex);
> +       list_for_each_entry(app, &aliases_lookup, link) {
> +               if (strcmp(app->stem, stem) != 0)
> +                       continue;
> +
> +               if (app->id > id)
> +                       id = app->id;
> +       }
> +       mutex_unlock(&of_mutex);
> +
> +       return id;
> +}
> +
>  struct device_node *of_get_stdout(void)
>  {
>         return of_stdout;
> diff --git a/include/dm/of_access.h b/include/dm/of_access.h
> index 5ed1a0cdb427..5cbfd220bfd4 100644
> --- a/include/dm/of_access.h
> +++ b/include/dm/of_access.h
> @@ -425,6 +425,15 @@ int of_alias_scan(void);
>  int of_alias_get_id(const struct device_node *np, const char *stem);
>
>  /**
> + * of_alias_get_highest_id - Get highest alias id for the given stem
> + * @stem:      Alias stem to be examined
> + *
> + * The function travels the lookup table to get the highest alias id for the
> + * given alias stem. It returns the alias id if found.

@return

> + */
> +int of_alias_get_highest_id(const char *stem);
> +
> +/**
>   * of_get_stdout() - Get node to use for stdout
>   *
>   * @return node referred to by stdout-path alias, or NULL if none
> --
> 1.9.1
>

Can we place have a test that calls this for a few values?

Also see uclass_find_next_free_req_seq() and uclass_resolve_seq()
which is what U-Boot does today. It is first in, first served. This is
supposed to mean that devices without an alias don't get a req_seq
value, meaning that the seq value is set to the next available value.

I suspect it is OK to change the behaviour though. It might affect
some boards which rely on not having aliases but still getting bus
numbers.

Regards,
Simon