> On Mar 22, 2017, at 3:34 AM, Johan Hovold <johan@xxxxxxxxxx> wrote: > > On Wed, Mar 22, 2017 at 11:19:10AM +0100, Greg Kroah-Hartman wrote: >> On Wed, Mar 22, 2017 at 02:26:52AM -0700, Greg Hazel wrote: >>> Hi, >>> >>> I’m working with Greybus and I’m wondering if there’s any support or >>> code for virtual USB devices. >> >> Yes, the USB virtual controller driver is in the kernel, but you need to >> have it enabled in your firmware as well, as it passes USB commands from >> the kernel down to the firmware and then USB device directly. > > The driver that's merged is far from complete I'm afraid. There was some > development happening out of tree, but the effort was discontinued and > the work in progress never merged back. Which side is not likely to work well? I can control the virtual device side, but not the host side. > >> Note, there are some limits on the size of a USB transaction at the >> moment, we never got the chance to fix them up, but small transactions >> (like a keyboard), should work fine. Once you start to get up to 4kb in >> a transaction, you might have firmware issues. > > That would even be 2k, and you'd still need the out-of-tree driver… 1500 bytes is the typical ethernet MTU, so even with overhead is 2k is reasonable? > >>> On one side of Greybus I have a small nuttX environment with a UART >>> connected device which I can write modules for, and on the other side >>> of Greybus I’d like to provide a network interface. I can’t modify >>> that side, so I have to work with the kernel modules it has available. >>> I thought it might be possible to present a virtual USB CDC-EVM to >>> Greybus, and my guess (hope) is that cdc_ether would pick it up on the >>> other side. >> >> Ah, if this isn't really a network device, or modem, I wouldn't mess >> with cdc-evm. If it is a modem, then it should "just work" with the >> uart code today, just tell userspace this is a modem and all should be >> fine. > > Indeed, that would be the way to go. This suggestion isn’t clear to me. The UART device is not a standard network device or modem; it needs some of my software to behave like one. I’d like to present it in a way that Greybus can provide to the host machine. cdc-evm was my first guess at that interface; but what do you think would be better? -Greg _______________________________________________ greybus-dev mailing list greybus-dev@xxxxxxxxxxxxxxxx https://lists.linaro.org/mailman/listinfo/greybus-dev
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