Subject: [PATCH v2] netpoll: Introduce netpoll_carrier_timeout kernel option

From: Anton Vorontsov <[email-masked]>
Date: Wed, 8 Jul 2009 05:30:11 +0400

Some PHYs require longer timeouts for carrier detection, and
auto-negotiation process may take indefinite amount of time.

It may be inconvenient to force longer timeouts for sane PHYs,
so let's introduce a kernel command line option.

Since we're using module_param(), the option also can be
changed in runtime.

Signed-off-by: Anton Vorontsov <[email-masked]>
---

On Tue, Jul 07, 2009 at 06:03:54PM -0700, Stephen Hemminger wrote:
> On Wed, 8 Jul 2009 05:00:30 +0400
> Anton Vorontsov <[email-masked]> wrote:
> 
> > Some PHYs require longer timeouts for carrier detection, and
> > auto-negotiation process may take indefinite amount of time.
> > 
> > It may be inconvenient to force longer timeouts for sane PHYs,
> > so let's introduce a kernel command line option.
> > 
> > Signed-off-by: Anton Vorontsov <[email-masked]>
> > ---
> >  Documentation/kernel-parameters.txt |    5 +++++
> >  net/core/netpoll.c                  |   11 ++++++++++-
> >  2 files changed, 15 insertions(+), 1 deletions(-)
> 
> A sysctl (or module option) is a less awkward interface for something
> like this.

Right you are, and it's less code. Wasn't sure if it makes sense
to use module_param() for non-modular code, but afterall it makes
sense indeed, since with it we can change the timeout in runtime.

> Kernel command line parameters are ugly step children
> loved only by embedded developers.

So true! ;-)

How about this patch?

Thanks,

 Documentation/kernel-parameters.txt |    5 +++++
 net/core/netpoll.c                  |    6 +++++-
 2 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index d77fbd8..9347f4a 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1531,6 +1531,11 @@ and is between 256 and 4096 characters. It is defined in the file
 			symbolic names: lapic and ioapic
 			Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
 
+	netpoll.carrier_timeout=
+			[NET] Specifies amount of time (in seconds) that
+			netpoll should wait for a carrier. By default netpoll
+			waits 4 seconds.
+
 	no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
 			emulation library even if a 387 maths coprocessor
 			is present.
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 9675f31..3afe381 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -9,6 +9,7 @@
  * Copyright (C) 2002  Red Hat, Inc.
  */
 
+#include <linux/moduleparam.h>
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/string.h>
@@ -50,6 +51,9 @@ static atomic_t trapped;
 static void zap_completion_queue(void);
 static void arp_reply(struct sk_buff *skb);
 
+static unsigned int carrier_timeout = 4;
+module_param(carrier_timeout, uint, 0644);
+
 static void queue_process(struct work_struct *work)
 {
 	struct netpoll_info *npinfo =
@@ -732,7 +736,7 @@ int netpoll_setup(struct netpoll *np)
 		}
 
 		atleast = jiffies + HZ/10;
-		atmost = jiffies + 4*HZ;
+		atmost = jiffies + carrier_timeout * HZ;
 		while (!netif_carrier_ok(ndev)) {
 			if (time_after(jiffies, atmost)) {
 				printk(KERN_NOTICE
-- 
1.6.3.3