On Fri, 31 Jul 2009, Viral Mehta wrote: > >> And my answer to this question is this is where modules.usbmap is used > >> and also when I connect USB device to my machine, some policy agents > >> reads modules.usbmap file and extracts information and must be calling > >> usbcore function. Then in turn usbcore will load/probe appropriate > >> device driver and NOT usbcore itself goes through list and decides about > >> which driver to load. > >> > > > > No, it is userspace that does this determination, not the kernel itself. > > A combination of udev and modprobe does the work. > > > If so, I strongly feel that below line from Documentation/hotplug.txt > should be removed/changed. > > "When the USB subsystem knows about a driver's device ID table, it's > used when choosing drivers to probe()..." > > The word "USB subsystem" creates confusion. It gives me a sense that > everything is happening BY usb subsytem FROM looking at driver's device > ID table and which is not true as discussed. Unfortunately, quite a lot of the material in Documentation/usb/hotplug.txt is sadly out of date. However the sentence you quoted is not. The sentence is accurate. "USB subsystem" refers to part of the kernel; there is no USB subsystem in userspace. Furthermore the udev and modprobe programs don't choose drivers to _probe_; they choose drivers to _load_. The decision about which drivers to probe is made entirely by the USB subsystem in the kernel, based on the drivers' device ID tables. Alan Stern -- 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
