On Mon, May 29, 2017 at 11:01:52AM +0200, Martin Fuzzey wrote:
> Hi Peter,
>
> I'm trying to create device tree nodes for USB devices (use case a USB
> device providing GPIO and I2C controllers)
>
> Your patch (now merged)
> 69bec725 "USB: core: let USB device know device node"
>
> looks just like what I need but I have a couple of problems.
>
> First it doesn't work at all on an i.MX53 because the actual struct
> device for the USB host controller is a "ci_hdrc" which is a child of
> the device having the DT node (ci_hdrc_imx)
I believe you should set the new sysdev pointer to the parent controller
device, which has the device tree node. Take a look at a8c06e407ef9
("usb: separate out sysdev pointer from usb_bus").
> However my larger question is that I don't see how to associate a DT
> node with a USB *interface* rather than a USB *device*.
I started looking into this a while back but got interrupted. I have
some preliminary code, mostly lacking associated documentation.
> For instance in my use case I will have a single USB device providing
> several USB interfaces (a composite device), including a GPIO controller
> and a I2C controller. So I need 2 DT nodes...
>
> There may be something in the the URL referenced in the binding doc
> (http://www.firmware.org/1275/bindings/usb/usb-1_0.ps)
> but that seems to be down (at least has been for the last few days).
Yes, it's been down for weeks (at least) now.
> Is this something missing, still in progress, or is each driver
> supposed to handle it on its own?
So yes, it's in progress.
> That would be *possible* something like:
>
> static int usb_gpio_probe(struct usb_interface *interface,
> const struct usb_device_id *id)
> {
> struct device *dev = &interface->dev;
> struct device_node *usb_dev_np = dev->parent->of_node;
>
> struct device_node *usb_itf_np = of_get_child_by_name(usb_dev_np,
> "gpio");
>
> ...
> }
>
> With
> &usbotg {
> #address-cells = <1>;
> #size-cells = <0>;
>
> hub_board {
> #address-cells = <1>;
> #size-cells = <0>;
> compatible = "pid,vid";
> reg = <1>;
>
> ext_usb {
> compatible = "pid2,vid2";
> reg = <2>;
>
> usb_gpio: gpio {
> }
> };
> };
> };
>
>
> But this doesn't seem like a very good idea since we're then likely to
> grow lots of different driver specific ways of doing the same thing.
> Eg above I used a child node named "gpio" but it would probably have
> been better to use the interface number in the node name in case there
> are several. And what about matching by interface class...
Indeed. We should declare the interfaces in DT instead.
> I think a "struct device_node *" should be added to struct usb_interface
> and the matching be done in the usb core code.
> Which means expressing in the DT as well all the different ways we can
> match a USB interface.
struct usb_interface already has a device-node pointer in it's embedded
struct device. All that is missing is to set it up.
I'll post my work as an RFC shortly, and add you on CC.
Thanks,
Johan
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