[lwip-users] Re: [lwip] sys_timeout()

[Peter Graf]

Hi!

>> Another way to make things easier to understand might be to pass a pointer
>> to the data structures used by the timeout implementation, when calling
>> sys_mbox_fetch() or sys_sem_wait().
>
>No, that would make the code that uses the OS emulation layer unnecessary 
>complex. I think it is more appropriate for the OS emulation layer to keep 
>track of things such as threads, timers and IPC mechanisms, and not the 
>application.

You're right. A little documentation someday will do.

Thanks to your explanation of the expected behaviour of sys_timeout() I've
been able to do an initial port to SMSQ/E the last weekend. As this
multitasking OS is based on a non-semaphore concept, I had to write my own
OS extension for semaphore support with timeout, in assembler. Ugly work. I
still seem to have bugs in there.

>The plans for the sys_arch layer in 0.5 is that the sys_mbox_fetch() and 
>sys_sem_wait() will take an additional argument that specifies the maximum 
>time to wait for the mailbox or the semaphore. The timer scheduling code 
>would then be moved out of the sys_arch file and into a generic sys.c file.

Very good idea. I don't know any OS which directly supports your kind of
timeout scheduling, so it must be implemented especially for lwIP anyway. I
don't see any additional performance cost.

>Anyway, thanks for your input and I am glad that the info helped!

Thanks to YOU!

Peter

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