Allows attaching multiple child busses in a mux topology
to an mctp-i2c instance on the root bus. In general I2C
slave mode does not make sense for mux busses, but the MCTP
request/response protocol means the the root can switch
between child muxes for incoming I2C messages.
Signed-off-by: Matt Johnston <matt@xxxxxxxxxxxxxxxxxxxx>
---
.../devicetree/bindings/net/mctp-i2c.yaml | 42 +++++++++++++++++--
1 file changed, 38 insertions(+), 4 deletions(-)
diff --git a/Documentation/devicetree/bindings/net/mctp-i2c.yaml b/Documentation/devicetree/bindings/net/mctp-i2c.yaml
index f9378cd845d4..45429cbcc6a1 100644
--- a/Documentation/devicetree/bindings/net/mctp-i2c.yaml
+++ b/Documentation/devicetree/bindings/net/mctp-i2c.yaml
@@ -12,11 +12,10 @@ maintainers:
description:
The MCTP I2C binding defines an MCTP endpoint on the I2C bus to
communicate with I2C peripherals using MCTP (DMTF specification DSP0237).
-
- An mctp-i2c device must be attached to a hardware bus adapter which supports
+ A single binding node can attach to multiple child busses in a mux topology.
+ An mctp-i2c node's parent must be a hardware bus adapter which supports
slave functionality. The reg address must include I2C_OWN_SLAVE_ADDRESS.
-
properties:
compatible:
const: mctp-i2c
@@ -24,6 +23,17 @@ properties:
reg:
maxItems: 1
+ bus-attach:
+ $ref: "/schemas/types.yaml#/definitions/phandle-array"
+ description: |
+ List of phandles of I2C busses to attach to. I2C mux busses may only
+ be attached to an mctp-i2c binding on their parent root adapter in the
+ mux topology.
+ If no bus-attach property is specified then only the direct parent
+ I2C bus is attached. Otherwise to include a direct parent bus it
+ must be included in the bus-attach list if needed.
+
+
additionalProperties: true
required:
@@ -33,12 +43,36 @@ required:
examples:
- |
#include <dt-bindings/i2c/i2c.h>
- i2c {
+
+ // simple attaching to a root adapter i2c0
+ i2c0: i2cbus0 {
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ mctp@50 {
+ compatible = "mctp-i2c";
+ reg = <(0x50 | I2C_OWN_SLAVE_ADDRESS)>;
+ };
+ };
+
+ // attaching to a root adapter i2c5 and a child mux bus i2c14
+ i2c5: i2cbus5 {
#address-cells = <1>;
#size-cells = <0>;
mctp@50 {
compatible = "mctp-i2c";
reg = <(0x50 | I2C_OWN_SLAVE_ADDRESS)>;
+ attach-bus = <&i2c5 &i2c14>;
};
};
+
+ i2cmux0 {
+ compatible = "i2c-mux-gpio";
+ #address-cells = <1>;
+ #size-cells = <0>;
+ i2c-parent = <&i2c0>;
+ i2c14: i2c@5 {
+ reg = <0>;
+ };
+ };
--
2.30.2
