Zitat von Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>:
On Thu, May 17, 2018 at 07:03:24PM +0200, Guido Kiener wrote:
The working group "VISA for Linux" of the IVI Foundation
www.ivifoundation.org specifies common rules, shared libraries and
drivers to implement the specification of "VPP-4.3: The VISA Library"
on Linux to be compatible with implementations on other operating systems.
The USBTMC protocol is part of the "VISA Library" that is used by many
popular T&M applications.
An initial implementation for Linux based on libusb has been created.
While functional it has some drawbacks:
- Performance
- Requires root privileges to reclaim devices already claimed by
the usbtmc driver
The following collaborative patches meet the requirements of the IVI
Foundation to implement the library based on the usbtmc driver.
Improvements in the data transfer rate of over 130 MByte/s for
usb 3.x connections have been measured.
Why is the libusb version "slower"? Last I checked, we could reach
line-speeds for USB quite easily from userspace with no problem. If you
keep the endpoints full you should be just fine. Unless you have a
horrid protocol that doesn't allow for that :)
Sorry, the wording is misleading. The performance of libusb is pretty well,
whereas the bandwidth of the current usbtmc driver is slow.
From my point of view the main advantage of the new usbtmc driver in
contrast to libusb is:
- Multiple applications can share access to the same instruments.
- The driver handles SRQ conflicts.
- usbtmc driver simplifies definition of udev rules
- usbtmc driver simplifies development of applications using T&M instruments.
thanks,
greg k-h
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