USB CDC performance test

[Mithran B]

On Mon, 7 Mar 2022 at 13:20, Greg KH <greg at kroah.com> wrote:

> On Mon, Mar 07, 2022 at 01:08:28PM +0530, Mithran B wrote:
> > On Fri, 4 Mar 2022 at 20:31, Greg KH <greg at kroah.com> wrote:
> >
> > > On Fri, Mar 04, 2022 at 08:06:55PM +0530, Mithran B wrote:
> > > > On Fri, 4 Mar 2022 at 19:48, Greg KH <greg at kroah.com> wrote:
> > > >
> > > > > On Fri, Mar 04, 2022 at 04:27:50PM +0530, Mithran B wrote:
> > > > > > Hello,
> > > > > >
> > > > > > In Host and Gadget systems, enabled the USB CDC drivers.
> > > > > > Then nodes are created as /dev/ttyAcm0 and /dev/ttyGs0.
> > > > > > Then opened the nodes and write and read back the data.
> > > > > > It is working.
> > > > > >
> > > > > > I want to test the performance of this interface and drivers.
> > > > > > Do we have any utility for this?
> > > > > > How to do the performance test?
> > > > >
> > > > > What exactly do you want to measure?  Determine that first before
> > > trying
> > > > > to find a test for that.  Without knowing what you want to measure,
> > > it's
> > > > > hard to tell you how to measure it :)
> > > > >
> > > > > good luck!
> > > > >
> > > > > greg k-h
> > > > >
> > > >
> > > > Thank you.
> > > > I want to send the data at the rate of 5mbps from Host device to
> target
> > > > device using USB CDC - ACM.
> > > > In termios functions, how to configure this 5mbps as baud rate and
> USB
> > > > payload size, i.e. packet
> > > > size to be in 2K bytes.
> > >
> > > There is no "baud rate" for usb cdc devices, really, as you have tried
> > > this already, right?
> > >
> > > Just send the data as fast as you can, with the largest chunks of data
> > > that you have (do not send it byte by byte to the kernel), and you
> > > should be fine.
> > >
> > > Are you sure that your device can handle that type of data rate?
> That's
> > > almost always the limiting factor.
> > >
> > > good luck!
> > >
> > > greg k-h
> > >
> >
> > In USB CDC, any software flow control mechanism is implemented?
>
> The specification is public on the usb.org web site, if you are curious.
> There is no need for "flow control" like you are used to for older
> serial connections with USB, the way USB works handles it automatically
> (the host drives the connection, if the device is full, it tells the
> host to wait automatically).
>
> > Any hardware flow control mechanism there?
>
> Other than the normal USB flow control mechanism?  No, why would there
> be?
>
> > How to enable this software flow control mechanism in kernel device
> drivers?
>
> what software flow control?
>
> > Any other information related to this is good for us.
>
> For whom?  What exactly have you tried and what were the results?
>
> thanks,
>
> greg k-h
>

Thank you. I got the details.
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