HDLC/PPP Driver

HDLC/PPP Driver

[Daris A Nevil]

I have receive several requests for information regarding the HDLC/PPP
driver in QSLinux.  In response I have put together a small white paper
describing the driver, and it is located at:

http://qslinux.org/docs/snmc/hdlc/index.html

Regards,
Daris

--
Daris A Nevil
Simple Network Magic Corporation
401 Kentucky Lane
McKinney, TX 75069
214-793-7757
dnevil@snmc.com
www.snmc.com
quickstack.com
qslinux.org

** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/

HDLC/PPP Driver

[Julia Elbert]

Hello,
Thank you for the white paper.
My problem is my hdlcppp is confused with enet. It appears my enet is
calling the xmit in hdlcppp after the enet open is called. Weird. How could
this happen? My enet is on SCC1 and hdlcppp is SCC2. Could some parameter in
hdlcppp have priority even when enet is loaded?
Thank you for your help. I hope this is not to elementary.
--Julia


http://qslinux.org/docs/snmc/hdlc/index.html


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Re: HDLC/PPP Driver

[Daris A Nevil]

Hi Julia,

I've not tested the HDLC/PPP driver on SCC2, so there could be a bug
lurking there.  Check the table named "SCC_Params" in the hdlcppp.c
file.  Also check to make sure that the constants in that table are
defined correctly in the associated .h files.

Other than that I can't figure out how the kernel would confuse the
network device "hdlcppp2" for "enet".  The hdlcppp.c file registers each
device using the "register_netdev()" function, and this relies on the
device name.

If it had been the receive function that was called by mistake then I
would suggest that the hdlc/ppp driver was overwriting the IRQ vector
table incorrectly.  But the transmit function,
hdlc_ppp_hard_start_xmit(), is called directly from the network stack
(sorry about the bogus comment in that function header).

Daris


Julia Elbert wrote:
>
> Hello,
> Thank you for the white paper.
> My problem is my hdlcppp is confused with enet. It appears my enet is
> calling the xmit in hdlcppp after the enet open is called. Weird. How could
> this happen? My enet is on SCC1 and hdlcppp is SCC2. Could some parameter in
> hdlcppp have priority even when enet is loaded?
> Thank you for your help. I hope this is not to elementary.
> --Julia
>
> http://qslinux.org/docs/snmc/hdlc/index.html
>

--
Daris A Nevil
Simple Network Magic Corporation
401 Kentucky Lane
McKinney, TX 75069
214-793-7757
dnevil@snmc.com
www.snmc.com
quickstack.com
qslinux.org

** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/

RE: HDLC/PPP Driver

[Julia Elbert]

Thank you, Darvis!

I was able to get your driver to load, configured, and pinging on the 860T.
Now, let me see if I can explain what happened.

I only wanted 1 SCC chanel, SCC2. I know you said that would not matter
until I actually configured hdlcppp2, but I think it did in the init in the
for {} where you go through all the PPP_HDLC_CHANNELS, because I am already
using SCC1, SCC3 and SCC4 at this point in other drivers.

It appears the line
dev->base_addr = (unsigned long)&cp->scc[i];
was the culprit.

I just forced i to 1 and used one PPP_HDLC_CHANNEL and my problems went
away. I was confused with this line a little because other drivers
initialize there drivers differently. Feel free to expand if you like

dev->base_addr = (unsigned long)&cp->scc[1];

The other indices with i were fine in the loop because i uses your
SCC_Params array which is fine.

Thought you would be interested.
Thank you, again. This kind of stuff makes my day and I enjoy learning from
the group.
--Julia


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