But VBUS switching bugs are easy to have on dual-role boards, so you should test this. The “bulk sink” and “bulk source” functionality is also supported by most peripheral firmware development kits, as is “iso sink” and “iso source” for hardware that supports isochronous transfers. It records audio data with a very specific sample rate which is based on the local oscillator of the device. Such core drivers include the hub driver which manages trees of USB devices and several different kinds of host controller drivers , which control individual busses. Sign up using Facebook. In fact, testing the hardware-specific controller driver relies on gadget zero and host side tests like these.

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Some host controllers have run these tests for weeks without significant problems; and since 2. Although most of these tests will be of interest to folk debugging, developing or maintaining USB system software like controller drivers or device firmware, some may be useful to sysadmins or isochronoys users that suspect they may have flakey USB hardware.

There’s a user-mode version of that driver, which optionally supports testing for a variety of isochronous transfer rates. Can fail if we are given bad arguments, or HCD is broken. Also, be sure to use a very recent Linux kernel; bugs in the test code do show up sometimes, and older kernels won’t have the fixes.


This is normally detected and reported from interrupt context. The test itself will only work on devices which isochronoud some testing-only control messages. This means that user mode driver may interfere other ones. See description for other values on failure.

After a successful call, the device may not yet be resumed. Note See USB 2.

Use ‘testusb -a’ to test all recognized devices in parallel one thread per device. Queues for isochronous endpoints are treated differently, because they must advance at fixed rates. This resets each endpoint in the interface.

linux – Isochronous USB transfers confusion – Stack Overflow

The same basic APIs are available to drivers for all those controllers. Sign up using Email and Password. As a rule, interrupt transfers are handled the same as bulk transfers; they shouldn’t need much separate testing. Issues a bulk read or write request to the device. Each such packet is an individual ISO transfer.

On systems without bus-snooping caches, these buffers are uncached. Races will show up a lot more readily!

The Linux-USB Host Side API

The simplest solution for most people will involve ordering a specialized PCI card and using it on a Linux PC; see below. It is not physically possible to assemble legal USB cables ub If you’re supporting Linux 2.

These are also the tests that might be helpful in turning up hardware problems with some USB configurations. Some peripherals can work through ‘usbfs’ with user mode device drivers; those peripherals tend to rely only on simple half-duplex protocols. It is guaranteed that upon return all completion handlers will have finished and the URB will be totally idle and available for reuse.


As with Gadget Zero, ussb this works for short periods you should ensure that it works reliably for days at isochrinous time. You might want to take a look at the official USB 2.

The possible error codes are: This is of course a data flow to the device, but on a lower protocol level Token Packets.

The collection of supported hardware is beginning to grow.

Isochronous iMX6 USB gadget example

There are several dozen of these tests, covering your device in both the “A” role default host and the “B” role default peripheral ; so make sure both host and peripheral side stacks isochronouz well before you start running these tests. The best full speed data rate is 19 packets of 64 bytes each per frame, or bytes per millisecond.

The same behavior and guarantee apply when an URB terminates because it was unlinked. Interrupt URBs must provide an interval, saying how often in milliseconds or, for highspeed devices, microsecond units to poll for transfers.