Re: [patch v5 2/2] dt-bindings: mfd: Add Device Tree bindings for Mellanox programmable devices

On Thu, 14 Sep 2017, Lee Jones wrote:

On Thu, 14 Sep 2017, Vadim Pasternak wrote:

quoted

The mlxreg a multifunction device driver handling LEDs, events, exposing
through sysfs reset signal, and reset causes info. These components share
a common register space.

Signed-off-by: Vadim Pasternak <redacted>
---
v4->v5:
 Comments pointed out by Rob:
 - Avoid duplications in reg;
 - Remove unnecessary details in description;
 - Do not use names like phandels;
 Changes added by Vadim:
 - Combine hotplug nodes interrupt aggregation, register offset and mask
   properties into hotplug-spec properties;
 - Combine reset, cause, etc subnodes register offset, mask and effective
   bit properties into attr-spec properties;
v3->v4:
 Comments pointed out by Rob:
 - Make a separate patch /devicetree/bindings/vendor-prefixes.txt;
 - Add .txt to Documentation/devicetree/bindings/mfd/mellanox,mlxreg-core
   and send it within this series;
 - Modify "compatible" property;
 - Modify explanation for "deferred" property;
 - Describe each subnode by its own section;
 - Don't use underscore in attribute names;
---
 .../bindings/mfd/mellanox,mlxreg-core.txt          | 165 +++++++++++++++++++++
 1 file changed, 165 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mfd/mellanox,mlxreg-core.txt

Wow!  I have never seen a binding like this before.

quoted

diff --git a/Documentation/devicetree/bindings/mfd/mellanox,mlxreg-core.txt b/Documentation/devicetree/bindings/mfd/mellanox,mlxreg-core.txt
new file mode 100644
index 0000000..1e3cce5
--- /dev/null
+++ b/Documentation/devicetree/bindings/mfd/mellanox,mlxreg-core.txt

@@ -0,0 +1,165 @@
+Mellanox programmable device control.
+-------------------------------------
+This binding defines the device control interface over for Mellanox BMC based
+switches.
+
+Required properties:
+- compatible =  "mellanox,mlxreg-i2c" or
+		"mellanox,mlxreg-i2c-16"
+
+- #address-cells : must be 1;
+- #size-cells : must be 0;
+- reg : I2C address;
+
+Optional properties:
+- interrupt-parent : phandle of parent interrupt controller;
+- interrupts : interrupt line;
+- deferred : I2C deferred bus phandle;
+	     I2C bus activation order enforce for the cases when hot-plug
+	     devices are attached to I2C bus, which is initialized after the
+	     I2C bus, where programmable device is attached;

Dependencies aren't usually expressed in DT.

Why can't this be done pragmatically?

Usually we try to interrogate a device that we depend on and if it's
not present, we return -EPROBE_DEFER and try again latter.

Actually, thinking about this.  Are these hierarchical?

If so, they would be better represented as a sub-node.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
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