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An i2c gate is useful to e.g. reduce the digital noise for RF tuners connected
to the i2c bus. Gates are similar to arbitrators in that you need to perform
some kind of operation to access the i2c bus past the arbitrator/gate, but
there are no competing masters to consider for gates and therefore there is
no arbitration happening for gates.

Common i2c gate properties.

- i2c-gate child node

Required properties for the i2c-gate child node:
- #address-cells = <1>;
- #size-cells = <0>;

Optional properties for i2c-gate child node:
- Child nodes conforming to i2c bus binding


Example :

	/*
	   An Invensense mpu9150 at address 0x68 featuring an on-chip Asahi
	   Kasei ak8975 compass behind a gate.
	 */

	mpu9150@68 {
		compatible = "invensense,mpu9150";
		reg = <0x68>;
		interrupt-parent = <&gpio1>;
		interrupts = <18 1>;

		i2c-gate {
			#address-cells = <1>;
			#size-cells = <0>;

			ax8975@c {
				compatible = "ak,ak8975";
				reg = <0x0c>;
			};
		};
	};
fields are written to on every packet forward and packet receive respectively. Thus if we are receiving packets from a particular fdb, they'll cause false-sharing with everyone who has looked it up (even if it didn't match, since mac/vid share cache line!). The "used" field is even worse since it is updated on every packet forward to that fdb, thus the standard config where X ports use a single gateway results in 100% fdb false-sharing. Note that this patch does not prevent the last scenario, but it makes it better for other bridge participants which are not using that fdb (and are only doing lookups over it). The point is with this move we make sure that only communicating parties get the false-sharing, in a later patch we'll show how to avoid that too. Signed-off-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/bridge')
-rw-r--r--net/bridge/br_private.h10
1 files changed, 6 insertions, 4 deletions
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h