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

[Sebastian Huber]

----- 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)