On Thu, Nov 02, 2006 at 06:29:02PM +0200, Constantine Kousoulos wrote: > Hello, > > I have a few questions regarding the usb drivers on the linux-2.6 > kernel. Try reading the USB chapter in the book, Linux Device Drivers, third edition (free online), as may of these questions should be answered there. > First of all, in order for a usb device to work, we need a host > controller. Linux has 3 host controller drivers (ohci, uhci, > ehci). Does it use only one of them or all three depending the > speed of the data transfer? It all depends on the USB host controller hardware. And we really have more than just 3, we have a lot of embedded controllers too that don't always follow the ohci/uhci/ehci model due to hardware issues. > Second, can the host controller talk directly to a usb device (eg > flash memory) or it has to cooperate with an appropriate driver > (eg mass-storage driver)? The host controller is dumb, it only handles sending USB "packets" to and from devices. > The point of all these is the following. In order to port linux's > usb support for, let's say, mass storage devices to another > system, what are the least needed parts for usb to work? Do i need > to just implement a host controller (eg ehci)? Or do i need to > port usb core + usb host + storage code from linux source? Just the host controller needs to work, once you have that up and running, all of the usb device drivers should work with no changes needed at all. Might I ask which hardware are you looking to get USB working on? There are lots of USB controllers already included in mainline, and others floating around in different trees. Perhaps your work is already done for you. Hope this helps, greg k-h -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
