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From:   Andrey Konovalov <andreyknvl@gmail.com>
Date:   Wed, 26 Jan 2022 23:12:41 +0100
Message-ID: <CA+fCnZe_p+JwUWwumgGm185vWSdAK_z-UFDp7-HWKANB4YjA=g@mail.gmail.com>
Subject: Re: [PATCH] usb: raw-gadget: fix handling of dual-direction-capable endpoints
To:     Jann Horn <jannh@google.com>
Cc:     Felipe Balbi <balbi@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        USB list <linux-usb@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Wed, Jan 26, 2022 at 9:52 PM Jann Horn <jannh@google.com> wrote:
>
> Under dummy_hcd, every available endpoint is *either* IN or OUT capable.
> But with some real hardware, there are endpoints that support both IN and
> OUT. In particular, the PLX 2380 has four available endpoints that each
> support both IN and OUT.
>
> raw-gadget currently gets confused and thinks that any endpoint that is
> usable as an IN endpoint can never be used as an OUT endpoint.
>
> Fix it by looking at the direction in the configured endpoint descriptor
> instead of looking at the hardware capabilities.
>
> With this change, I can use the PLX 2380 with raw-gadget.
>
> Fixes: f2c2e717642c ("usb: gadget: add raw-gadget interface")
> Signed-off-by: Jann Horn <jannh@google.com>
> ---
>  drivers/usb/gadget/legacy/raw_gadget.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/usb/gadget/legacy/raw_gadget.c b/drivers/usb/gadget/legacy/raw_gadget.c
> index c5a2c734234a..d86c3a36441e 100644
> --- a/drivers/usb/gadget/legacy/raw_gadget.c
> +++ b/drivers/usb/gadget/legacy/raw_gadget.c
> @@ -1004,7 +1004,7 @@ static int raw_process_ep_io(struct raw_dev *dev, struct usb_raw_ep_io *io,
>                 ret = -EBUSY;
>                 goto out_unlock;
>         }
> -       if ((in && !ep->ep->caps.dir_in) || (!in && ep->ep->caps.dir_in)) {
> +       if (in != usb_endpoint_dir_in(ep->ep->desc)) {
>                 dev_dbg(&dev->gadget->dev, "fail, wrong direction\n");
>                 ret = -EINVAL;
>                 goto out_unlock;
>
> base-commit: 0280e3c58f92b2fe0e8fbbdf8d386449168de4a8
> --
> 2.35.0.rc0.227.g00780c9af4-goog
>

Awesome! Thanks for finding this!

What do you think about using

if ((in && !ep->ep->caps.dir_in) || (!in && !ep->ep->caps.dir_out))

instead?

It looks less cryptic: if (in and no in caps) or (out and no out caps) => fail.

FTR, I tested both changes with the net2280 hardware that I have, and
they work. At least gadget.c from the test suite enumerates properly.
Most of the tests still fail. But with g_zero, even more of them fail.

P.S. I wonder why everyone suddenly got interested in Raw Gadget lately? :)