linux-kernel - Re: [tip:x86/doc] x86/doc: mini-howto for using earlyprintk=dbgp

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Date:	Thu, 05 Mar 2009 15:48:41 -0800
From:	Daniel Walker <dwalker@...o99.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Yinghai Lu <yinghai@...nel.org>, mingo@...hat.com, hpa@...or.com,
	linux-kernel@...r.kernel.org, randy.dunlap@...cle.com,
	ebiederm@...ssion.com, akpm@...ux-foundation.org, gregkh@...e.de,
	tglx@...utronix.de, sarah.a.sharp@...el.com, mingo@...e.hu,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/doc] x86/doc: mini-howto for using earlyprintk=dbgp

On Thu, 2009-03-05 at 17:54 -0500, Alan Stern wrote:
> On Thu, 5 Mar 2009, Daniel Walker wrote:
> 
> > Fix up some typos, and make the requirements section slightly cleaner.
> > 
> > Signed-Off-By: Daniel Walker dwalker@...o99.com
> > 
> > diff --git a/Documentation/x86/earlyprintk.txt b/Documentation/x86/earlyprintk.txt
> > index 607b1a0..5b51aef 100644
> > --- a/Documentation/x86/earlyprintk.txt
> > +++ b/Documentation/x86/earlyprintk.txt
> > @@ -9,7 +9,9 @@ and two USB cables, connected like this:
> >  
> >  1. There are three specific hardware requirements:
> >  
> > - a.) Host/target system needs to have USB debug port capability.
> > + a.) You will need two USB ports. One on the client/console system and one one the target system.
> 
> s/one one/one on/
> 
> You might also try harder to observe the 80-column rule.
> 
> > + 
> > + b.) The client/console and target USB ports must have the debug port capability.
> >  
> >   You can check this capability by looking at a 'Debug port' bit in
> >   the lspci -vvv output:
> > @@ -35,15 +37,13 @@ and two USB cables, connected like this:
> >  ( If your system does not list a debug port capability then you probably
> >    wont be able to use the USB debug key. )
> >  
> > - b.) You also need a Netchip USB debug cable/key:
> > + c.) You also need a Netchip USB debug cable/key:
> >  
> >          http://www.plxtech.com/products/NET2000/NET20DC/default.asp
> >  
> >       This is a small blue plastic connector with two USB connections,
> >       it draws power from its USB connections.
> 
> No.  It draws power from one of its USB connections (the one on the 
> right side when you're looking at the face with the PLX logo).
> 
> Alan Stern

--

Fix up some typos, and make the requirements section slightly cleaner.
Updated the power draw comment per Alan Stern.

Signed-Off-By: Daniel Walker <dwalker@...o99.com>

diff --git a/Documentation/x86/earlyprintk.txt b/Documentation/x86/earlyprintk.txt
index 607b1a0..ac913a6 100644
--- a/Documentation/x86/earlyprintk.txt
+++ b/Documentation/x86/earlyprintk.txt
@@ -9,7 +9,11 @@ and two USB cables, connected like this:
 
 1. There are three specific hardware requirements:
 
- a.) Host/target system needs to have USB debug port capability.
+ a.) You will need two USB ports. One on the client/console system and one on 
+     the target system.
+ 
+ b.) The client/console and target USB ports must have the debug port
+     capability.
 
  You can check this capability by looking at a 'Debug port' bit in
  the lspci -vvv output:
@@ -35,14 +39,13 @@ and two USB cables, connected like this:
 ( If your system does not list a debug port capability then you probably
   wont be able to use the USB debug key. )
 
- b.) You also need a Netchip USB debug cable/key:
+ c.) You also need a Netchip USB debug cable/key:
 
         http://www.plxtech.com/products/NET2000/NET20DC/default.asp
 
      This is a small blue plastic connector with two USB connections,
-     it draws power from its USB connections.
-
- c.) Thirdly, you need a second client/console system with a regular USB port.
+     it draws power from one of its USB connections (the one on the 
+     right side when you're looking at the face with the PLX logo).
 
 2. Software requirements:
 
@@ -54,7 +57,7 @@ and two USB cables, connected like this:
 
     And you need to add the boot command line: "earlyprintk=dbgp".
     (If you are using Grub, append it to the 'kernel' line in
-     /etc/grub.conf)
+     grub.conf (i.e. /boot/grub/grub.conf) )
 
     NOTE: normally earlyprintk console gets turned off once the
     regular console is alive - use "earlyprintk=dbgp,keep" to keep
@@ -72,7 +75,7 @@ and two USB cables, connected like this:
 
     Now this channel of kernel messages is ready to be used: start
     your favorite terminal emulator (minicom, etc.) and set
-    it up to use /dev/ttyUSB0 - or use a raw 'cat /dev/ttyUSBx' to
+    it up to use /dev/ttyUSBx - or use a raw 'cat /dev/ttyUSBx' to
     see the raw output.
 
  c.) On Nvidia Southbridge based systems: the kernel will try to probe
@@ -92,7 +95,7 @@ and two USB cables, connected like this:
 
    On the client/console system do:
 
-       cat /dev/ttyUSB0
+       cat /dev/ttyUSBx
 
    And you should see the help line above displayed shortly after you've
    provoked it on the host system.


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