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

[Simon Glass]

Hi Michal,

On Thu, 31 Jan 2019 at 03:19, Michal Simek <michal.simek at xilinx.com> wrote:
>
> On 31. 01. 19 11:04, Simon Glass wrote:
> > 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.
> >
>
> Let me play with it and see that calling sequence.
>
>
> > 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.
>
> Do you mean with I2C? Or different buses?
>
> I don't think there is any affected board with DM_I2C and OF_CONTROL
> because unlisted aliases are using req_seq -1 now.

Yes I think that is right, actually.

Regards,
SImon