[RFC PATCH 1/2] USB: core: let USB device know device node

On Fri, Jan 08, 2016 at 08:32:45AM -0600, Rob Herring wrote:

On Thu, Jan 7, 2016 at 11:44 PM, Peter Chen [off-list ref] wrote:

quoted

Although most of USB devices are hot-plug's, there are still some devices
are hard wired on the board, eg, for HSIC and SSIC interface USB devices.
If these kinds of USB devices are multiple functions, and they can supply
other interfaces like i2c, gpios for other devices, we may need to
descirbe these at device tree.

In this commit, it uses "reg" in dts as port number to match the port
number decided by USB core, if they are the same, then the device node
is for the device we are creating for USB core.

Signed-off-by: Peter Chen <redacted>
---
 .../devicetree/bindings/usb/usb-device.txt         |  8 ++++
 drivers/usb/core/Makefile                          |  2 +-
 drivers/usb/core/of.c                              | 48 ++++++++++++++++++++++
 drivers/usb/core/usb.c                             |  8 +++-
 include/linux/usb.h                                |  2 +
 include/linux/usb/of.h                             |  6 +++
 6 files changed, 71 insertions(+), 3 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/usb/usb-device.txt
 create mode 100644 drivers/usb/core/of.c

diff --git a/Documentation/devicetree/bindings/usb/usb-device.txt b/Documentation/devicetree/bindings/usb/usb-device.txt
new file mode 100644
index 0000000..d35facd
--- /dev/null
+++ b/Documentation/devicetree/bindings/usb/usb-device.txt

@@ -0,0 +1,8 @@
+Generic USB Device Properties
+
+Usually, we only use device tree for hard wired USB device.
+The reference binding doc is from:
+http://playground.sun.com/1275/bindings/usb/usb-1_0.ps.

This path doesn't exist anymore. Use
http://www.firmware.org/1275/bindings/usb/usb-1_0.ps

Ok.

quoted

+
+Required properties:
+- reg: the port number which this device is connecting to.

At least compatible should also be here.

What format for USB device compatible string has still not been decided.
Would you suggest something? At my example, I use "vid,pid".

quoted

+ */
+struct device_node *usb_of_find_node(struct device_node *parent, int portnum)
+{
+       struct device_node *node;
+       u32 port;
+
+       for_each_child_of_node(parent, node) {
+               if (!of_property_read_u32(node, "reg", &port)) {
+                       if (port == portnum)
+                               return node;

This needs to match on the compatible string too. Otherwise, this
could match in lots of cases.

No, the port number is unique under the USB HUB (including host
controller, which is roothub), and there are some many compatible
string for USB devices.

-- 

Best Regards,
Peter Chen