API to convert priorities to/from POSIX from/to Classic?

[Joel Sherrill]

On Mon, Jul 30, 2018 at 1:03 PM, Sebastian Huber <
sebastian.huber at embedded-brains.de> wrote:

> ----- Am 30. Jul 2018 um 18:29 schrieb Gedare Bloom gedare at rtems.org:
>
> > On Mon, Jul 30, 2018 at 11:23 AM, Joel Sherrill <joel at rtems.org> wrote:
> >>
> >>
> >> On Mon, Jul 30, 2018 at 7:43 AM, Sebastian Huber
> >> <sebastian.huber at embedded-brains.de> wrote:
> >>>
> >>> On 30/07/18 14:25, Joel Sherrill wrote:
> >>>>
> >>>>
> >>>>
> >>>> On Mon, Jul 30, 2018, 6:26 AM Sebastian Huber
> >>>> <sebastian.huber at embedded-brains.de
> >>>> <mailto:sebastian.huber at embedded-brains.de>> wrote:
> >>>>
> >>>>     Hello,
> >>>>
> >>>>     is there a standard API to convert priorities to/from POSIX
> from/to
> >>>>     Classic? If not, I think we should add something.
> >>>>
> >>>>
> >>>> There is not a public API for this.  There are some internal helpers
> >>>
> >>>
> >>> Do you know the name of the helpers?
> >>
> >>
> >> I was thinking of the _RTEMS_Priority_To_Core,
> >> _RTEMS_Priority_From_core, and the similar
> >> POSIX helper.
> >>
> >> These are probably useful to some users. No real
> >> cost to applications that don't use them.
> >>
> >
> > These convert between the core kernel notion of priority and the api.
> > I see no problem to add some wrappers like
> >
> > rtems_posix_priority_to_core() and from_core(), and
> > rtems_priority_to_core(), and from_core().
> >
> > A user then could convert between the two APIs themselves if they need,
> like
> > rtems_priority_from_core( rtems_posix_priority_to_core(p) );
> >
> > I would not introduce any conversion between classic and posix
> > priorities directly. It is violation of the API independence.
>
> I don't like the idea to expose an internal priority thing to the user. We
> would have to create an API representation of something scheduler-specific.
>
> I propose:
>
> scheduler_id == RTEMS_SELF == scheduler of executing thread
>
> rtems_status_code rtems_task_priority_posix_to_classic(rtems_id
> scheduler_id, int posix_priority, rtems_task_priority *classic_priority)
> rtems_status_code rtems_task_priority_classic_to_posix(rtems_id
> scheduler_id, rtems_task_priority classic_priority, int *posix_priority)
>


For the simplest case of current scheduler, what does a call look like?

And honestly, I wouldn't be opposed to something like this if it has a use
case:

rtems_task_priority rtems_get_self_priority(void)

The Classic API (e.g. RTEID/ORKID) reflects a period in API programming
where
you wanted a small API set. Accessors were not separated out. Methods to
simply get some information or state of an object were not included.
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