USB, Host and Device on the same machine

USB, Host and Device on the same machine

[Fredrik Johansson]

Hello

I am working on an embedded machine that has two USB controllers, one
is a OTG and the other is a pure host.

I have succesfully used g_serial driver on the OTG controller in
device mode and talked to my pc using the cdc-acm driver.
With the g_serial unloaded I have also enabled the ehci-hcd and
cdc-acm drivers and connected the host port to another serial device.

The problem I have now is that I want to be able to have my embedded
machine work as a device on the OTG port and a host on the host port,
but if I load the ehci-hcd driver with g_serial already loaded it
screws everything up since ehci-hcd driver attaches to both the OTG
and the host controller, how can i prevent it from using the OTG
controller?

Best regards
Fredrik Johansson

Re: USB, Host and Device on the same machine

[Ming Lei]

2008/10/24 Fredrik Johansson <frejo242-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>:
> Hello
>
> I am working on an embedded machine that has two USB controllers, one
> is a OTG and the other is a pure host.
>
> I have succesfully used g_serial driver on the OTG controller in
> device mode and talked to my pc using the cdc-acm driver.
> With the g_serial unloaded I have also enabled the ehci-hcd and
> cdc-acm drivers and connected the host port to another serial device.
>
> The problem I have now is that I want to be able to have my embedded
> machine work as a device on the OTG port and a host on the host port,
> but if I load the ehci-hcd driver with g_serial already loaded it
> screws everything up since ehci-hcd driver attaches to both the OTG
> and the host controller, how can i prevent it from using the OTG
> controller?

It is a platform dependent problem.  what is your platform ?( musb? )
which buses do the otg controller and ehci controller attache to?

>
> Best regards
> Fredrik Johansson
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Re: USB, Host and Device on the same machine

[David Brownell]

On Friday 24 October 2008, Fredrik Johansson wrote:
> if I load the ehci-hcd driver with g_serial already loaded it
> screws everything up since ehci-hcd driver attaches to both the OTG
> and the host controller, how can i prevent it from using the OTG
> controller?

If the OTG controller exposes EHCI as its host interface, it
sure *ought* to be managed by the EHCI driver.  Maybe you
should be submitting a patch adding OTG glue to EHCI?

If it's not exposing EHCI as its host interface, then it seems
your OTG driver is quite buggy...

Re: USB, Host and Device on the same machine

[Fredrik Johansson]

> If the OTG controller exposes EHCI as its host interface, it
> sure *ought* to be managed by the EHCI driver.  Maybe you
> should be submitting a patch adding OTG glue to EHCI?
>
> If it's not exposing EHCI as its host interface, then it seems
> your OTG driver is quite buggy...
>

Thanks for the advice.
The OTG controller was exposed as a host and it was my fault...
It was a miss in my kernel config where I had enabled host
functionality on the OTG controller, disabling host functionality
solved the problem since I only want to use it as a device.

Regards

Fredrik Johansson