[En-Nut-Discussion] detecting an unplugged network cable

[Ulrich Prinz]

Hi!

I actually rework the at91_emac.c and found some problems regarding the 
PHY handling. Unfortunately the PHY is the first one that recognizes a 
cable disconnect. But the EMAC can detect this too, I guess. But it then 
needs to do something. First thing to do should be to ask the PHY what 
has happened on the front side. Instead the stack thinks, that the EMAC 
has faulted and resets it again and again.

I rewrote the PHY part for the AT91 only. Now I need to glue it more 
tight to the EMAC part. After that I can find out how to more elegantly 
detect error conditions.
A disconnected cable should be the easy thing to find out.

But I am not sure if the whole registration is done correctly the way 
you did it.
NutRegisterDevice() should not fail, cable connected or not. It 
initializes the hardware and does basic setup.
Then normally DHCP is started and that one will fail if the cable is not 
in and fall back to fixed address. Then further packages sent or or 
requested will fail too.
So there is a function missing that gives more detailed information 
about the network status.

So I started to add a EmacCtl that can be called for detecting EMAC and 
PHY states and control some functions.
But I am not finished yet. But with this you can detect the network 
stack state more friendly. It should not be needed to re-register the 
complete device but only restart the logical stack and request a new IP 
via DHCP if enabled.

Oh, AFAIK the DHCP is a thread that runs autonomously. It must be one as 
a lease may expire and it must request a new lease. So there must be a 
mechanism that keeps track of the connection. Unfortunately it cannot 
detect the unplugged situation as this is not provided by the EMAC/PHY 
driver.
Ok, looks like there is some work still open.

Best regards,
Ulrich

Am 08.11.2010 15:15, schrieb elbric0:
> Hi!
>
> Thanks for your answers. It's a good idea to run network stuff in a thread. However I still have a problem with NutRegisterDevice. When the network cable is unplugged, it takes a little more than three minutes before it returns an error. And it doesn't seems to yield the cpu as long as it is running.
>
> I have this code in my network thread:
>
> NutThreadSetPriority(128);
> while (NutRegisterDevice(&DEV_ETHER, 0, 0))
> {
>          puts("\tFailed. Retrying in 10 sec.");
>          NutSleep(10000);    /* Sleep for 10 sec */
> }
>
> I didn't change the priority of the main task. So I assume it is 64. The main task should print the time every minute.
>
> When the network cable is unplugged, the "Failed" message and the time are both printed every 3 minutes. So I am quite sure that NutRegisterDevice blocks for all that time.
>
> Is it the normal behavior?
>
> Best regards
>
> Jasmin
>
>
> Le 2010-11-08 à 06:16, Ulrich Prinz a écrit :
>
>> Hi!
>>
>> The driver itself detects that fact and does not start ethernet. To not
>> get blocked by DHCP you should run DHCP as a thread. The httpd example
>> is not a good reference or that, I think.
>> I am actually reworkign that part... The new PHY driver can give you
>> the information if the cable is connected. But it can take a while for
>> AutoNegotiation to link up and you have to wait that time until the
>> system times out....
>>
>> Nope, the best way is to start network an DHCP in a thread. Anything
>> else doesn't work.
>>
>> Best Regards
>> Ulrich
>>
>>
>> -----Original Message-----
>> From: elbric0<elbric0 at f-m.fm>
>> To: en-nut-discussion at egnite.de
>> Sent: Mon, Nov 8, 2010 1:47 am
>> Subject: [En-Nut-Discussion] detecting an unplugged network cable
>>
>>
>> Hi,I would like to detect if a network cable is unplugged at boot time
>> and skip everything related to network when it is the case.
>> NutRegisterDevice(&DEV_ETHER, 0, 0) returns an error after a long while
>> when the cable is unplugged. It is possible to use that, but it is a
>> little annoying as is makes boot time quite long. Is there another way
>> to make the check or a way to make NutRegisterDevice return faster?Best
>> RegardsJasmin_______________________________________________http://lists.
>> egnite.de/mailman/listinfo/en-nut-discussion
>>
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