On 03/11/2011 04:45 PM, Somebody in the thread at some point said: Hi -
Or to put it another way... With external, hot-plugged USB devices, there is no need to know "how it is wired". The fact that it is on a USB bus is the only information necessary. Why does anyone need to know more than this for on-board USB devices?
For example, the USB device is a chip with option pins. On the board it is placed on, some of the option pins are tied in a particular way that impacts its actual function, but can't be seen from the chip itself. The driver covers all the options, but it needs to be told which mode the chip was wired up for.
Another example, it's a USB chip with GPIO pins, analogous to a I2C GPIO extender. Some of the GPIO are wired to LEDs also on the board, which you want to expose as generic GPIO. The board definition file is in a position to do all that because it knows what the board is and what it is wired up to.
That the USB chips in these examples are 'discoverable' has nothing to do with anything. In fact the board definition file has knowledge about the "functional implemntation" of the instances of those chips -- just exactly those instances soldered to the board. If you plugged another of these chips, the board definition file has nothing to say about it because they are not "on the board" and in-scope for it.
-Andy -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
