Re: [lwip-users] Stackless, non-preemptive uSmartX RTOS and lwIP

[Christiaan Simons]

address@hidden wrote on 26-01-2000
17:57:05:

> I have already passed through the lwIP sources and documentation. If I
> understand well it can works in two modes. The so called raw api and
> sequential api mode. The raw api mode doesn't require an underlying
> RTOS, but the latter does. The raw API mode should be easy and straight
> forward to integrate into my os.

We've used it for most of our lwip based projects, I can recommend it.
The sequential API is currently unmaintained, but it might work for some
ports.

> The sequential API looks a little bit tricky if the os is
> not-preemptive. If you look at the sample code below you can get an idea
> of how for example semaphores are used in my rtos. Basically they
> require the task to return if the resource is not available. The task
> will be than resumed by a semaphore post or a timeout event. Applying
> this to lwIP would require modification of the API calls in such a way
> that multiple calls of the same API call can be made if the semaphore is
> not available at the moment and than calling the same API function with
> "semaphore" available parameter...

Reading through doc/sys_arch.txt I get the impression
the usage of a preemptive kernel is assumed.

Using a non-preemptive kernel seems a bit odd nowadays.
I believe OSEK is one of the last one providing it.

> Now I am kindly referring to you for some comments on this
> implementation. I'm also a little bit confused on sequential API calls -
> which file contains the available calls ? Is this api_msg.c, sockets or
> some other additional file ?

There are two layers on top of each other.
The api_msg provides the actual serialisation,
the socket layer just builds upon this layer.
You can use both layers.

Bye,

Christiaan Simons


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