On Saturday 04 April 2015 12:08:36 Florian Fainelli wrote: > Le 30/03/2015 12:35, Alan Stern a écrit : > > On Mon, 30 Mar 2015, Valentin Longchamp wrote: > > > >> Hello, > >> > >> We are currently developing a board with an USB MFD device (I2C and GPIOs > >> are to > >> be supported). The device is soldered on the board and is the only one on > >> the > >> bus, so the bus is not really "dynamic". > >> > >> Since it's an USB device, it should be dynamically detected by the kernel > >> and it > >> would not require a node in the board's DTS. However, I need to have the > >> devices > >> which are "behind" the MFD USB device to be in the DTS (I2C bus topology, > >> and > >> some of the GPIOs are to be used directly by some other DTS nodes as well). > >> > >> Is there a way to add a node for USB device in a DTS ? Is there an > >> available > >> example for this ? > > > > No, there is no way to do it as far as I know. The main problem is > > that Device Tree is static whereas USB devices are dynamic. > > The PCI(e) bus has the same problem, yet you can specify a PCI device > child node, and have a compatible string which will match the vendor > id/device id tuple, device class etc... such that you can use Device > Tree to add additional information not necessarily available in other > ways such as MAC addresses and similar. > > Once the PCI bus is scanned, pci_device present in Device Tree get a > device_node pointer assigned. > > I don't think there is anything doing this yet for USB devices, but > maybe that's something that should be there? >
It's come up a number of times. Basically we should support this, and I believe it's relatively straightforward to do, someone just has to implement it, but setting the of_node pointer for a USB device that gets added and if that has a matching node. There is a binding for USB that we never implemented in Linux. It used to be at http://playground.sun.com/1275/bindings/usb/usb-1_0.ps and I can send a copy to anyone that needs one. Most of the contents are irrelevant unless you want to implement a full Open Firmware rather than a flattened device tree. The important parts are: #address-cells: needs to be 1 #size-cells: needs to be 0 reg: 'The "reg" property for a device node shall consist of the number of the USB hub port or the USB host controller port to which this USB device is attached. As specified in [2] section 11.11.2.1, port numbers range from 1 to 255.' Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
