RE: [lwip-users] netif->flags

[John Kennedy]

Ok, thanks everyone this group is extremely responsive and I appreciate 
everyone's help.  Simon as always you are correct (albeit sometimes a bit 
terse) I did lump everything together.  From my overall perspective the goal is 
the same: get Ethernet working on my embedded system.  Not knowing much about 
Ethernet, I find it quite daunting to wade through all the ports, drivers, and 
Lwip code, moreover many of the embedded ports I've looked at have some obvious 
problems and I don't know a lot about Windows or Unix/Linux so those ports 
don't make a lot of sense to me.  I've spent a lot of time grepping around in 
the source code but that doesn't help much trying to understand the overall 
architecture of the code or it's intended usage.  Thanks again,
John


 
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John Kennedy


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-----Original Message-----
From: Simon Goldschmidt [mailto:address@hidden
Sent: Monday, May 18, 2009 11:39 PM
To: Mailing list for lwIP users
Subject: RE: [lwip-users] netif->flags


> Jeff,
> That makes sense to me, I was just a little puzzled by why Lwip doesn't
> set NETIF_FLAG_UP with the rest of the flags in low_level_init and why there
> is no comment or anything else I can find that indicates that it even needs
> to be set.  Hence my original question.

You're mixing responsibilities here: you have to separate between 'lwIP', 
'port' and 'netif driver'. lwIP cannot know when the netif is up! You *could* 
set it up in the driver by setting the flag in low_level_init (a function of 
that lwIP itself knows nothing!), but that would prevent the handling in 
netif_set_up.

Which brings us to the last, the 'port'. Have a look at the example ports in 
contrib (always a good idea with questions like this):
netif_add(&netif, addresses...)
netif_set_up(&netif)
netif_set_default(&netif) // only for the one and only default netif

> but it does not initialize the flag NETIF_FLAG_UP.

It does: it's off by default!

> I can’t find anywhere else in the code where this flag is set.

I'm guessing that question is answered by reading the code...?

Simon
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