netdev - [PATCH] net: phy: Add config option to specify external switch port to be used if switch is used as PHY

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Date:	Thu, 8 Sep 2011 08:54:07 +0200
From:	Lambrecht Jürgen <J.Lambrecht@...EVIC.com>
To:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:	"linux-embedded@...r.kernel.org" <linux-embedded@...r.kernel.org>
Subject: [PATCH] net: phy: Add config option to specify external switch port
 to be used if switch is used as PHY

Hello,

In our embedded designs, this is a useful patch. Maybe it can be useful 
for somebody else too.
Or maybe there are already better solutions?
I know I could also write a driver for our switch, but that is too much 
effort just to select the active port.

Kind regards,
Jürgen

   In embedded design, instead of a PHY, sometimes a switch is used that
           behaves as a PHY through its MII port. For example to use a daisy
           chain network configuration instead of an expensive star config.
           In that case, many phy ports are available, but only 1 should 
be used
           to check link status, and not the first one available as is 
the case
           without this configuration (that is, set to its default value 0).
           So this options specifies the switch port number to be used 
to check
           link status, because if the link is down, no data is sent by the
           TCP/IP stack.

Signed-off-by: Jürgen Lambrecht <J.Lambrecht@...evic.com>
---
  drivers/net/phy/Kconfig    |   14 ++++++++++++++
  drivers/net/phy/mdio_bus.c |    9 +++++++++
  2 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
index a702443..554561f 100644
--- a/drivers/net/phy/Kconfig
+++ b/drivers/net/phy/Kconfig
@@ -13,6 +13,20 @@ menuconfig PHYLIB

  if PHYLIB

+config SWITCH_PHY
+       int "External switch port to be used if switch is used as PHY"
+       default "0"
+       help
+         In embedded design, instead of a PHY, sometimes a switch is 
used that
+         behaves as a PHY through its MII port. For example to use a daisy
+         chain network configuration instead of an expensive star config.
+         In that case, many phy ports are available, but only 1 should 
be used
+         to check link status, and not the first one available as is 
the case
+         without this configuration (that is, set to its default value 0).
+         So this options specifies the switch port number to be used to 
check
+         link status, because if the link is down, no data is sent by the
+         TCP/IP stack.
+
  comment "MII PHY device drivers"

  config MARVELL_PHY
diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c
index 6c58da2..016437a 100644
--- a/drivers/net/phy/mdio_bus.c
+++ b/drivers/net/phy/mdio_bus.c
@@ -112,7 +112,14 @@ int mdiobus_register(struct mii_bus *bus)
         if (bus->reset)
                 bus->reset(bus);

+       /* The config below is always availble with CONFIG_PHYLIB. If 0, the
+          behavior is as before without this patch (or P0 of the switch is
+          taken because it is the first one found). */
+#if CONFIG_SWITCH_PHY
+       i = CONFIG_SWITCH_PHY;
+#else
         for (i = 0; i < PHY_MAX_ADDR; i++) {
+#endif
                 if ((bus->phy_mask & (1 << i)) == 0) {
                         struct phy_device *phydev;

@@ -122,7 +129,9 @@ int mdiobus_register(struct mii_bus *bus)
                                 goto error;
                         }
                 }
+#if !CONFIG_SWITCH_PHY
         }
+#endif

         bus->state = MDIOBUS_REGISTERED;
         pr_info("%s: probed\n", bus->name);
--
1.7.1