Writing USB Device Driver in Linux

ALSA or libusb api are two choices; both are new to me; its been years since I wrote a device driver and it was for Unix back in the 80's, but I do know I can figure out how, once I know what tools to use, which I'm guessing 开发者_如何学Goboth use C still; I have looked at the libusb api; very nice; but I have no idea about ALSA project; seems they are geared into getting modules into the kernel to achieve this.

This is a generic question, but the Device I'm interested in is the Roland GR-55; it has MIDI and Audio from the same USB connection; it has Windows and MAC Drivers but no Linux.

Which libraries or tools do you prefer to use?

Do I write a Device Driver or Loadable Kernel Modules (LKM)?

libusb is useful and easy to get up and running. I would suggest that you start there, especially if you haven't written Linux drivers in a while. Use libusb to understand what the signalling protocol is for the Roland GR-55 and do some experiments.

USB supports several types of logical connections over the same physical wire. There will likely be DATA and CONTROL pipes available from the device and you will need to map that out before starting on a proper driver.

As I said, libusb is easy to get going and you could have something useful in a few days if you just want to write a control interface and store raw data from the device. However, ALSA is the way to go if you want to use the device with existing music software. Also, by updating ALSA you would be supporting the larger community because you could merge your work in to the ALSA project.

Writing a kernel module from scratch could be fun, but USB is a bit of a beast and would probably not be an ideal one to start with. With ALSA you will have a framework to guide you and won't need to worry so much about defining your own APIs.

As commented above, check out Linux Device Drivers http://lwn.net/Kernel/LDD3/ chapter 13 talks specifically about USB drivers. For development it's easier to write your driver as a kernel module because then you don't need to recompile the kernel when you make a change.

No need for writing a new driver - ALSA already has support for that since a while. See commit https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=0ef283247a0cf0fd2e8370ee467030292eb3129e

Since you probably want to hear sound on your sound card, you should opt for ALSA. That way after you are done you are done. If you write libusb driver, then you would have to write your own user space tools for feeding that sound card sound for playing.