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Diffstat (limited to 'Documentation/networking/switchdev.txt')
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diff --git a/Documentation/networking/switchdev.txt b/Documentation/networking/switchdev.txt new file mode 100644 index 0000000..f981a92 --- /dev/null +++ b/Documentation/networking/switchdev.txt @@ -0,0 +1,59 @@ +Switch (and switch-ish) device drivers HOWTO +=========================== + +Please note that the word "switch" is here used in very generic meaning. +This include devices supporting L2/L3 but also various flow offloading chips, +including switches embedded into SR-IOV NICs. + +Lets describe a topology a bit. Imagine the following example: + + +----------------------------+ +---------------+ + | SOME switch chip | | CPU | + +----------------------------+ +---------------+ + port1 port2 port3 port4 MNGMNT | PCI-E | + | | | | | +---------------+ + PHY PHY | | | | NIC0 NIC1 + | | | | | | + | | +- PCI-E -+ | | + | +------- MII -------+ | + +------------- MII ------------+ + +In this example, there are two independent lines between the switch silicon +and CPU. NIC0 and NIC1 drivers are not aware of a switch presence. They are +separate from the switch driver. SOME switch chip is by managed by a driver +via PCI-E device MNGMNT. Note that MNGMNT device, NIC0 and NIC1 may be +connected to some other type of bus. + +Now, for the previous example show the representation in kernel: + + +----------------------------+ +---------------+ + | SOME switch chip | | CPU | + +----------------------------+ +---------------+ + sw0p0 sw0p1 sw0p2 sw0p3 MNGMNT | PCI-E | + | | | | | +---------------+ + PHY PHY | | | | eth0 eth1 + | | | | | | + | | +- PCI-E -+ | | + | +------- MII -------+ | + +------------- MII ------------+ + +Lets call the example switch driver for SOME switch chip "SOMEswitch". This +driver takes care of PCI-E device MNGMNT. There is a netdevice instance sw0pX +created for each port of a switch. These netdevices are instances +of "SOMEswitch" driver. sw0pX netdevices serve as a "representation" +of the switch chip. eth0 and eth1 are instances of some other existing driver. + +The only difference of the switch-port netdevice from the ordinary netdevice +is that is implements couple more NDOs: + + ndo_switch_parent_id_get - This returns the same ID for two port netdevices + of the same physical switch chip. This is + mandatory to be implemented by all switch drivers + and serves the caller for recognition of a port + netdevice. + ndo_switch_parent_* - Functions that serve for a manipulation of the switch + chip itself (it can be though of as a "parent" of the + port, therefore the name). They are not port-specific. + Caller might use arbitrary port netdevice of the same + switch and it will make no difference. + ndo_switch_port_* - Functions that serve for a port-specific manipulation. |
