[lwip-users] Sys_timeouts

[Bilahari Akkiraju]

Hello all, thank you for answers to my queries. I still don't get the complete 
idea of sys_timeouts. The documentation says it's a linked list of structures 
per thread that is used by lwip timeout scheduler. Where and with what should I 
populate this linked list. 

     One more thing I don't understand is why is sys_arch_mbox_fetch there but 
not sys_arch_mbox_post ?. 

I am  running on a bare platform and I have my own working OS services ( 
scheduler, semaphores, message queues) and I feel that I should have my own 
sys.c, ie my own API layer so that I need not worry about timeouts. Is sys.c 
the api layer you were talking about when you said "if you have your own API 
layer, you can ignore timeouts". ?

Thanks
Bilahari

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Today's Topics:

   1. RE: Example port for a beginner (Goldschmidt Simon)
   2. RE: Antw: RE: [lwip-users] pbuf_header fails in etharp_output
      (Kieran Mansley)
   3. RE: Example port for a beginner (Goldschmidt Simon)
   4. RE : [lwip-users] Example port for a beginner (Fr?d?ric BERNON)
   5. RE: RE : [lwip-users] Example port for a beginner
      (Goldschmidt Simon)
   6. RE: RE : [lwip-users] Example port for a beginner (Kieran Mansley)
   7. RE : tcp ack problem (Fr?d?ric BERNON)


----------------------------------------------------------------------

Message: 1
Date: Wed, 23 May 2007 09:48:55 +0200
From: "Goldschmidt Simon" <address@hidden>
Subject: RE: [lwip-users] Example port for a beginner
To: "Mailing list for lwIP users" <address@hidden>
Message-ID:
        <address@hidden>
Content-Type: text/plain;       charset="us-ascii"

> 2. Can I port lwip stack without implementing sys_arch.c at all. I
mean without impelementing semaphore and mailbox funcs.

For that you have to set NO_SYS to 1 in lwipopts.h but you can only use the 
callback API then (no sockets, no netconn API). You also don't need the 
sys_arch.h and sys_arch.c file (if you take other ports as an example).

> 3 . Should I change or add some stuff in sys.c like in sys_arch.c. 

You should not need to change sys.c! sys_arch.c is dependent on your OS.


Simon




------------------------------

Message: 2
Date: Wed, 23 May 2007 09:04:39 +0100
From: Kieran Mansley <address@hidden>
Subject: RE: Antw: RE: [lwip-users] pbuf_header fails in etharp_output
To: Mailing list for lwIP users <address@hidden>
Message-ID: <address@hidden>
Content-Type: text/plain

On Wed, 2007-05-23 at 08:19 +0200, Matthias Weisser wrote:
> >>>> that there is room at the front for the necessary headers.  I 
> >>>> suppose if your ethernet driver was being very efficient and had 
> >>>> stripped off the ethernet header before creating the pbuf, this 
> >>>> might not be the case.  Can you show how you're
> >>>
> >>> Yes, that's what I am doing.
> >>>
> >> In that case it's technically the fault of lwIP and we should 
> >> perhaps change our ICMP to not do this (or at least check the pbuf 
> >> to see if it's OK before it does).  If you'd rather not work around 
> >> it, please file a bug so that it will eventually get fixed.
> > 
> > Yes, please file a bug report!
> 
> About what? That ip_input fails if the IP header is not 4 byte 
> aligned? Or that etharp_output fails if there is no room at the 
> beginning of a p_buf to store the ethernet header?

That ICMP assumes the pbuf you give it has space for a ethernet header at the 
front.

Kieran





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Message: 3
Date: Wed, 23 May 2007 10:46:45 +0200
From: "Goldschmidt Simon" <address@hidden>
Subject: RE: [lwip-users] Example port for a beginner
To: "Mailing list for lwIP users" <address@hidden>
Message-ID:
        <address@hidden>
Content-Type: text/plain;       charset="us-ascii"

> 4    Yes sys_timeouts  is pretty confusing but if you implement your
own api layer then you can ignore it all together 

That's not exactly true: if NO_SYS=0, you
a) have to supply a function in sys_arch.c (if NO_SYS=0) that returns a pointer 
to a list of timeouts that is unique for the current thread
B) have to make sure the value returned by sys_arch_mbox_wait() (and
sys_arch_sem_wait()) is correct (the number of miliseconds waited for a 
message)!

If you want to know more about timeouts: it is a linked list including function 
pointers and values of miliseconds to wait before calling the function. When 
waiting for a message in an mbox, the time waited is substracted from the first 
timeout, and if that time is 0, the timeout function is called and the first 
item is popped off the list.
This mechanism only works if NO_SYS=0 since otherwise, you don't have mboxes. 
But if you have mboxes, you kind of get the timeout functionality for free.
The downside of this approach is that the timing is pretty inaccurate.
If you have many messages in the mbox and you will not have to wait on any 
message, sys_arch_mbox_wait() will always return 0 since it didn't have to wait 
for the message. That way timeouts will not be called.
Another bad example are some ports that always return 1 when waiting for a 
message and 0 if a message was available right away. That of course leads to 
totally inaccurate timeouts.


Simon




------------------------------

Message: 4
Date: Wed, 23 May 2007 10:56:05 +0200
From: Fr?d?ric BERNON <address@hidden>
Subject: RE : [lwip-users] Example port for a beginner
To: "Mailing list for lwIP users" <address@hidden>
Message-ID: <address@hidden>
Content-Type: text/plain; charset="iso-8859-1"

>That's not exactly true... 
I suppose that Mumtaz talk to a "full" api layer, even without api_msg.c & 
tcpip.c, so, I think in this case, it''s right

>If you want to know more about timeouts:  
It's a good explain, I think it will be good to copy/paste it in sys_arch.txt 
and sys.c...
  
====================================
Frédéric BERNON
HYMATOM SA
Chef de projet informatique
Microsoft Certified Professional
Tél. : +33 (0)4-67-87-61-10
Fax. : +33 (0)4-67-70-85-44
Email : address@hidden
Web Site : http://www.hymatom.fr
====================================
P Avant d'imprimer, penser à l'environnement
 


-----Message d'origine-----
De : address@hidden [mailto:address@hidden De la part de Goldschmidt Simon 
Envoyé : mercredi 23 mai 2007 10:47 À : Mailing list for lwIP users Objet : RE: 
[lwip-users] Example port for a beginner


> 4    Yes sys_timeouts  is pretty confusing but if you implement your
own api layer then you can ignore it all together 

That's not exactly true: if NO_SYS=0, you
a) have to supply a function in sys_arch.c (if NO_SYS=0) that returns a pointer 
to a list of timeouts that is unique for the current thread
B) have to make sure the value returned by sys_arch_mbox_wait() (and
sys_arch_sem_wait()) is correct (the number of miliseconds waited for a 
message)!

If you want to know more about timeouts: it is a linked list including function 
pointers and values of miliseconds to wait before calling the function. When 
waiting for a message in an mbox, the time waited is substracted from the first 
timeout, and if that time is 0, the timeout function is called and the first 
item is popped off the list. This mechanism only works if NO_SYS=0 since 
otherwise, you don't have mboxes. But if you have mboxes, you kind of get the 
timeout functionality for free. The downside of this approach is that the 
timing is pretty inaccurate. If you have many messages in the mbox and you will 
not have to wait on any message, sys_arch_mbox_wait() will always return 0 
since it didn't have to wait for the message. That way timeouts will not be 
called. Another bad example are some ports that always return 1 when waiting 
for a message and 0 if a message was available right away. That of course leads 
to totally inaccurate timeouts.


Simon


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Message: 5
Date: Wed, 23 May 2007 11:12:58 +0200
From: "Goldschmidt Simon" <address@hidden>
Subject: RE: RE : [lwip-users] Example port for a beginner
To: "Mailing list for lwIP users" <address@hidden>
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        <address@hidden>
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> >That's not exactly true... 
> I suppose that Mumtaz talk to a "full" api layer, even without 
> api_msg.c & tcpip.c, so, I think in this case, it''s right

That's what I meant with "if NO_SYS=0". But you're right, maybe for a beginner, 
that's not as clear as I wanted it to be...

> 
> >If you want to know more about timeouts:  
> It's a good explain, I think it will be good to copy/paste it in 
> sys_arch.txt and sys.c...

In that way, we finally get some documentation done ;-)




------------------------------

Message: 6
Date: Wed, 23 May 2007 10:27:09 +0100
From: Kieran Mansley <address@hidden>
Subject: RE: RE : [lwip-users] Example port for a beginner
To: Mailing list for lwIP users <address@hidden>
Message-ID: <address@hidden>
Content-Type: text/plain

On Wed, 2007-05-23 at 11:12 +0200, Goldschmidt Simon wrote:
> > >If you want to know more about timeouts:  
> > It's a good explain, I think it will be good to copy/paste it in 
> > sys_arch.txt and sys.c...
> 
> In that way, we finally get some documentation done ;-)

Yes please - there have been a number of good explanations recently 
(particularly from Simon) that I've thought would make good beginnings of 
documentation.  I suggest that for now we create something in CVS (if there's 
no relevant place already) so that you can easily copy and past these things in 
when writing such stuff to the mailing list.  This will be much easier than 
trying to find them later when writing docs!

Kieran





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Message: 7
Date: Wed, 23 May 2007 11:32:27 +0200
From: Fr?d?ric BERNON <address@hidden>
Subject: [lwip-users] RE : tcp ack problem
To: "cui_hengbin98" <address@hidden>,   "Mailing list for lwIP
        users" <address@hidden>
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