RE: [lwip-users] Query on NO_SYS in opts.h

[Goldschmidt Simon]

Hi,

I tell you the other way around:

> #define NO_SYS

With NO_SYS=1, you can only use the callback API (in other words
you can't use anything in the 'api' directory). You have to poll
your MAC and give the received packets to ip_input(). You also
have to call all the necessary timer functions at the appropriate
intervals. See http://www.sics.se/~adam/lwip/os.html "The lwIP
single-threaded core" for an example.

> #define SYS_LIGHTWEIGHT_PORT

Is an enhancment introduced later to be able to use some functions
from interrupt context also (mainly memp_malloc/memp_free). With
SYS_LIGHTWEIGHT_PORT=1, you're supoosed to be able to free pbufs
in interrupt context (e.g. after a transmit interrupt with a DMA
enabled MAC). This of course makes the whole stasck slower as
interrupts have to be locked often. Note that freeing PBUF_RAM
pbufs from interrupt context doesn't really work right now since
the heap (mem_malloc) is locked by a semaphore...


Hope that helps!


Simon