netdev - Re: [PATCH ethtool] ethtool: Warn if we cannot set the advertising mask for specified speed/duplex

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Message-ID: <1298044598.2570.4.camel@bwh-desktop>
Date:	Fri, 18 Feb 2011 15:56:38 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	netdev@...r.kernel.org
Cc:	linux-net-drivers@...arflare.com,
	Naveen Chouksey <nchouksey@...arflare.com>
Subject: Re: [PATCH ethtool] ethtool: Warn if we cannot set the advertising
 mask for specified speed/duplex

On Thu, 2011-02-17 at 19:06 +0000, Ben Hutchings wrote:
> When autonegotiation is enabled, drivers must determine link speed and
> duplex through the autonegotiation process and will generally ignore
> the speed and duplex specified in struct ethtool_cmd.  If the user
> specifies a recognised combination of speed and duplex, we set the
> advertising mask to include only the matching mode.  Otherwise, we
> advertise all supported modes.  We should really limit the advertised
> modes separately by speed and duplex, but for now we just warn.
> 
> Signed-off-by: Ben Hutchings <bhutchings@...arflare.com>
> ---
> This is a longstanding bug in ethtool which people keep getting bitten
> by.  Naveen was just the latest to report it.  I have been working on
> some changes to improve link advertising and reporting, but until those
> are ready I'm adding this warning.

That patch fixes an additional bug: we will now update the advertising
mask based on speed/duplex when autoneg is already on.  Unfortunately it
introduces a bug: we will update advertising even if none of autoneg,
speed or duplex are specified!

Here's a second version which I think will do the right thing in all
cases, though I haven't tested it yet.  I'll include this in ethtool
2.6.38 if no-one can spot a flaw.

Ben.

---
From: Ben Hutchings <bhutchings@...arflare.com>
Date: Thu, 17 Feb 2011 18:51:15 +0000
Subject: [PATCH ethtool] ethtool: Don't silently ignore speed/duplex when autoneg is on

When autonegotiation is enabled, drivers must determine link speed and
duplex through the autonegotiation process and will generally ignore
the speed and duplex specified in struct ethtool_cmd.  Currently, if
the user specifies autoneg on but does not specify the advertising
mask then:

- If the user specifies a recognised combination of speed and duplex,
  we set the advertising mask to the flag for that mode.  (Currently
  only one mode is recognised per combination of speed and duplex.)
- Otherwise, we advertise all recognised and supported modes.

But we should also set the advertising mask if autoneg is *already*
on.  Also, we should be able to limit the advertised modes separately
by speed and duplex.  For now, we just warn if we fail to do that.

Signed-off-by: Ben Hutchings <bhutchings@...arflare.com>
---
 ethtool.c |   45 +++++++++++++++++++++++++++++++--------------
 1 files changed, 31 insertions(+), 14 deletions(-)

diff --git a/ethtool.c b/ethtool.c
index 1afdfe4..2f4b6ee 100644
--- a/ethtool.c
+++ b/ethtool.c
@@ -1126,7 +1126,7 @@ static void parse_cmdline(int argc, char **argp)
 		}
 	}
 
-	if ((autoneg_wanted == AUTONEG_ENABLE) && (advertising_wanted < 0)) {
+	if (advertising_wanted < 0) {
 		if (speed_wanted == SPEED_10 && duplex_wanted == DUPLEX_HALF)
 			advertising_wanted = ADVERTISED_10baseT_Half;
 		else if (speed_wanted == SPEED_10 &&
@@ -2528,19 +2528,36 @@ static int do_sset(int fd, struct ifreq *ifr)
 				ecmd.phy_address = phyad_wanted;
 			if (xcvr_wanted != -1)
 				ecmd.transceiver = xcvr_wanted;
-			if (advertising_wanted != -1) {
-				if (advertising_wanted == 0)
-					ecmd.advertising = ecmd.supported &
-						(ADVERTISED_10baseT_Half |
-						 ADVERTISED_10baseT_Full |
-						 ADVERTISED_100baseT_Half |
-						 ADVERTISED_100baseT_Full |
-						 ADVERTISED_1000baseT_Half |
-						 ADVERTISED_1000baseT_Full |
-						 ADVERTISED_2500baseX_Full |
-						 ADVERTISED_10000baseT_Full);
-				else
-					ecmd.advertising = advertising_wanted;
+			/* XXX If the user specified speed or duplex
+			 * then we should mask the advertised modes
+			 * accordingly.  For now, warn that we aren't
+			 * doing that.
+			 */
+			if ((speed_wanted != -1 || duplex_wanted != -1) &&
+			    ecmd.autoneg && advertising_wanted == 0) {
+				fprintf(stderr, "Cannot advertise");
+				if (speed_wanted >= 0)
+					fprintf(stderr, " speed %d",
+						speed_wanted);
+				if (duplex_wanted >= 0)
+					fprintf(stderr, " duplex %s",
+						duplex_wanted ? 
+						"full" : "half");
+				fprintf(stderr,	"\n");
+			}
+			if (autoneg_wanted == AUTONEG_ENABLE &&
+			    advertising_wanted == 0) {
+				ecmd.advertising = ecmd.supported &
+					(ADVERTISED_10baseT_Half |
+					 ADVERTISED_10baseT_Full |
+					 ADVERTISED_100baseT_Half |
+					 ADVERTISED_100baseT_Full |
+					 ADVERTISED_1000baseT_Half |
+					 ADVERTISED_1000baseT_Full |
+					 ADVERTISED_2500baseX_Full |
+					 ADVERTISED_10000baseT_Full);
+			} else if (advertising_wanted != -1) {
+				ecmd.advertising = advertising_wanted;
 			}
 
 			/* Try to perform the update. */
-- 
1.7.3.4



-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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