On Tue, 2011-10-04 at 07:57 -0700, Greg KH wrote: > On Tue, Oct 04, 2011 at 04:36:06PM +0200, Jack Smith wrote: > > On Sat, 2011-10-01 at 07:08 -0700, Greg KH wrote: > > > On Sat, Oct 01, 2011 at 03:00:14PM +0200, jack wrote: > > > > > > > > I am hoping to do some work on the USB MTP (Media Transfer Protocol) > > > > driver. Reading linux/drivers/usb/README has left me a bit confused, > > > > since it seems the location for the MTP driver would not be within the > > > > USB directory (linux/drivers/usb) or subdirectories, but rather would > > > > reside somewhere within linux/drivers/media. However, I don't see > > > > anything that is identified as a MTP driver for a USB device within that > > > > directory. > > > > > > > > Can you help clear up my confusion about this? > > > > > > I'm pretty sure that MTP support for Linux is done as a userspace driver > > > using gadgetfs. If you search the archives for the linux-usb mailing > > > list, you will find a link to where the source code is located, as it > > > has been posted in the past. > > > > > > Hope this helps, > > > > > > greg k-h > > > > OK, now I feel more confused. I thought: "The <linux/usb_gadget.h> API > > makes it easy for peripherals and other devices embedding GNU/Linux > > system software to act in the USB "device" (slave) role." > > http://www.linux-usb.org/gadget/ > > Yes. > > > Doesn't that mean that gadget API can be used by USB device > > manufacturers who want an Open Source solution for the device's USB > > functionality? To be more clear, isn't that API used on the device > > itself, and not for a Linux loadable module to be used by my workstation > > machine with that device plugged in to the USB port? > > Yes, that's what I thought you were looking for, sorry, I was confused. > No problem. I'm glad that I was able to understand that much ;-) > If you want the host side of the MTP solution, that too is done in > userspace, no kernel driver needed. I think it's in the gphoto library > code that uses libusb to talk to the devices. I'd recommend digging > around in that. > OK, so, can I ask why this is done in user space, instead of as a kernel module ? Also, why are some USB protocols are handled as drivers, e.g. Mass Storage, while others are not ? Pardon me asking, but why the inconsistency ? > Hope this helps, > Yes, very helpful, but: The thing is, I really want to work on device drivers. It seemed like USB-MTP would be a good candidate since USB is clearly not going away, and MTP seems fairly poorly supported within Linux (unless I'm missing something). > greg k-h -- 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
