Re: [Discuss-gnuradio] libusb-0.1 versus libusb-1.0

[Thomas Tsou]

On Fri, May 27, 2011 at 1:08 AM, Brett L. Trotter <address@hidden> wrote:
> So after discovering that while I had libusb-devel-0.1 and
> libusb1-devel-1.0.3 installed on my RHEL-6 machine here (and ubuntu),
> gnuradio compiled against 0.1 despite 0.1 being "ancient and
> unsupported". I then removed libusb-devel and gnuradio fails to configure.

libusb-1.0 isn't used unless specified.

./configure --with-fusb-tech=libusb1

> So just what is the status with libusb. Should it be compiling against
> libusb-0.1 or should it be compiling against libusb-1.0 and if so, why
> isn't configure finding libusb-1.0 on Ubuntu or RHEL-6?

Either (if not UHD). The differences are minor, though the reasons are
more subtle.

A quick search may reveal that libusb-1.0 supports asynchronous I/O
which is substantially faster than its predecessor, but this is
deceiving with regards to gnuradio. The libusrp driver worked around
limitations of libusb-0.1 through a hybrid case of using underlying -
platform specific - calls (usbfs in the case of Linux) where high
throughput was needed.

libusb-1.0 adds a layer on top of the kernel interfaces and the
platform specific calls are removed. Since the libusb-1.0 asynchronous
interface is largely modelled after the Linux kernel interface, this
layer is "thin" and the differences are negligible in the most cases.

  Thomas