Since carrier handling is often done incorrectly by new device drivers
be explicit about carrier handling API.
Signed-off-by: Stephen Hemminger <redacted>
---
This is a meant as starting point for discussion, it's probably wrong as is.
Since this isn't code, it could be applied for 3.6 and doesn't need for net-next.
--- a/Documentation/networking/netdevices.txt 2012-06-22 08:27:46.729168196 -0700
+++ b/Documentation/networking/netdevices.txt 2012-08-15 08:56:31.120429994 -0700
@@ -45,6 +45,36 @@ drop, truncate, or pass up oversize pack
packets is preferred.
+CARRIER
+=======
+Most network devices have an operational state that the device
+monitors. The Linux kernel uses the name "carrier" for this flag which
+is a historical reference to old modems. Carrier is reported to
+userspace via the IFF_RUNNING flag from SIOCGIFFLAGS ioctl.
+Carrier is controlled in the device driver
+by the functions netif_carrier_on and netif_carrier_off. These
+functions trigger the necessary netlink and userspace API changes;
+device drivers must not change netdevice->flags directly.
+
+The carrier defaults to ON when the device is created and registered.
+Simple devices (such as dummy) do not need to do anything.
+Ethernet style devices should:
+ * alloc_etherdev in probe routine
+ * call netif_carrier_off
+ * register network device
+ * start auto negotiation with phy in open routine
+ * call netif_carrier_on when link is up
+
+More complex RFC2863 style operational state is also possible
+but not required (see operstates.txt).
+
+The monitoring of link state is the responsibility of the network
+device driver. It can be done by polling, interrupt, or any other
+mechanism. netif_carrier_on/netif_carrier_off are atomic and can
+safely be called by an interrupt routine. Carrier events are
+managed by the linkwatch work queue and limited to one per second
+to avoid overwhelming management applications.
+
struct net_device synchronization rules
=======================================
ndo_open:
On Wed, 2012-08-15 at 08:58 -0700, Stephen Hemminger wrote:
quoted hunk
Since carrier handling is often done incorrectly by new device drivers
be explicit about carrier handling API.
Signed-off-by: Stephen Hemminger <redacted>
---
This is a meant as starting point for discussion, it's probably wrong as is.
Since this isn't code, it could be applied for 3.6 and doesn't need for net-next.
--- a/Documentation/networking/netdevices.txt 2012-06-22 08:27:46.729168196 -0700
+++ b/Documentation/networking/netdevices.txt 2012-08-15 08:56:31.120429994 -0700
@@ -45,6 +45,36 @@ drop, truncate, or pass up oversize pack
packets is preferred.
+CARRIER
+=======
+Most network devices have an operational state that the device
+monitors. The Linux kernel uses the name "carrier" for this flag which
+is a historical reference to old modems. Carrier is reported to
+userspace via the IFF_RUNNING flag from SIOCGIFFLAGS ioctl.
+Carrier is controlled in the device driver
+by the functions netif_carrier_on and netif_carrier_off. These
+functions trigger the necessary netlink and userspace API changes;
+device drivers must not change netdevice->flags directly.
+
+The carrier defaults to ON when the device is created and registered.
+Simple devices (such as dummy) do not need to do anything.
+Ethernet style devices should:
+ * alloc_etherdev in probe routine
+ * call netif_carrier_off
+ * register network device
+ * start auto negotiation with phy in open routine
Auto-negotiation is only one of several stages of link setup, and of
course is not used in all Ethernet physical layers. I think the
important point is that once the ndo_open method returns the hardware
and driver should be ready to set up the link and report this state
whenever a suitable partner is physically connected.
+ * call netif_carrier_on when link is up
+
+More complex RFC2863 style operational state is also possible
+but not required (see operstates.txt).
Drivers are not allowed to set operstate directly.
+The monitoring of link state is the responsibility of the network
+device driver. It can be done by polling, interrupt, or any other
+mechanism. netif_carrier_on/netif_carrier_off are atomic and can
+safely be called by an interrupt routine. Carrier events are
+managed by the linkwatch work queue and limited to one per second
+to avoid overwhelming management applications.
+
struct net_device synchronization rules
=======================================
ndo_open:
--
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.
On Wednesday 2012-08-15 17:58, Stephen Hemminger wrote:
quoted hunk
--- a/Documentation/networking/netdevices.txt 2012-06-22 08:27:46.729168196 -0700
+++ b/Documentation/networking/netdevices.txt 2012-08-15 08:56:31.120429994 -0700
@@ -45,6 +45,36 @@ drop, truncate, or pass up oversize pack
packets is preferred.
+CARRIER
+=======
+Most network devices have an operational state that the device
+monitors. The Linux kernel uses the name "carrier" for this flag which
+is a historical reference to old modems. Carrier is reported to
+userspace via the IFF_RUNNING flag from SIOCGIFFLAGS ioctl.
I think Netlink should be mentioned instead:
Carrier is reported to userspace via the IFF_RUNNING flag in
struct ifinfomsg.ifi_flags returned by RTM_GETLINK (see rtnetlink(7)).