Per-BSP confdefs (or resource allocation)

[Isaac Gutekunst]

On 10/22/2015 10:30 AM, Joel Sherrill wrote:
>
>
> On 10/22/2015 8:55 AM, Isaac Gutekunst wrote:
>> On 10/22/2015 01:33 AM, Sebastian Huber wrote:
>>>
>>>
>>> On 21/10/15 21:53, Isaac Gutekunst wrote:
>>>> Hi Devel,
>>>>
>>>> I looked for a while, but couldn't find a way to specify what resources (semaphores, tasks,
>>>> etc) a BSP requires for an empty project (empty Init function).
>>>
>>> There is no useful support for this and this is a constant source of problems.
>>>
>>> One way out of this situation would be to use self-contained objects for the drivers.
>>>
>>>>
>>>> I took a look at this page:
>>>> https://docs.rtems.org/doc-current/share/rtems/html/bsp_howto/Initialization-Code-The-RTEMS-Configuration-Table.html
>>>>
>>>> but couldn't glean the correct method.
>>>>
>>>> What is the preferred way to do so?
>>>>
>>>> Our BSP uses a number of resources for hardware drivers, including UART, CAN, SPI, I2C and
>>>> Ethernet.
>>>>
>>>>
>>>
>>> In case an empty project includes all these drivers, then something is wrong with this BSP.
>>>
>> That's good to know. Is it advisable to have all the drivers disabled by default? Of course, at
>> minimum a BSP needs a console driver.
>
> Technically a BSP doesn't even need that. Many applications field without one.
> The clock tick is technically also optional but that is almost universally required
> by applications. The minimum BSP technically only needs to startup and shutdown.
>
> But if you want to link/run all the tests, you need a console, clock tick, and
> benchmark timer driver.
>
> I have seen bspstart.c or other initialization files pull in more than minimum
> required. I have also seen bugs in Makefile.am that result in the entire BSP
> being a binary blob always linked in.
I'm not sure whether our Makefile.am is done correctly. As we move forward with getting it 
merged into mainline, I'm sure we'll get some useful feedback.

>
>> Our console driver does use one task, and one or more mutexes. Is this something we should try
>> hard to change?
>
> Why does it use so many resources? The termios framework provides all the
> buffering internally and confdefs.h accounts for them.

I was a bit confused. Talking to Jay and looking at the code, the termios console does not use 
any additional kernel resources.

We do use additional resources to expose serial ports via a raw interface (IMFS) to bypass the 
termios overhead. The kernel drivers for these are still in our branch, not mainline.


It looks like for our case, the two areas that use additional resources are for two new "device 
classes", CAN and raw UART that aren't present in the kernel. If we get these new drivers 
merged into the RTEMS kernel at some point (perhaps after living in the BSP for a while, to 
shake out bugs), we can update confdefs.h to account for those resources since at that point, 
they will have the potential to be used in other BSPs.


Isaac
>
> --joel