On 12/11/2017 09:58 AM, Alan Stern wrote:
> The URB_NO_FSBR flag has never really been used. It was introduced as
> a potential way for UHCI to minimize PCI bus usage (by not attempting
> full-speed bulk and control transfers more than once per frame), but
> the flag was not set by any drivers.
>
> There's no point in keeping it around. This patch simplifies the API
> by removing it. Unfortunately, it does have to be kept as part of the
> usbfs ABI, but at least we can document in
> include/uapi/linux/usbdevice_fs.h that it doesn't do anything.
>
> Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
>
> ---
>
> Shuah, I'm not sure if this will cause an interoperability problem for
> usbip. In theory, a machine running an older kernel might set the
> URB_NO_FSBR flag when communicating with a new kernel, which would
> cause an error. But I don't know any reason why even an old kernel
> would ever set the flag.
Alan, I am not sure how the interoperability will manifest.
<snip>
> ===================================================================
> --- usb-4.x.orig/drivers/usb/core/urb.c
> +++ usb-4.x/drivers/usb/core/urb.c
> @@ -479,9 +479,6 @@ int usb_submit_urb(struct urb *urb, gfp_
> if (is_out)
> allowed |= URB_ZERO_PACKET;
> /* FALLTHROUGH */
> - case USB_ENDPOINT_XFER_CONTROL:
> - allowed |= URB_NO_FSBR; /* only affects UHCI */
> - /* FALLTHROUGH */
> default: /* all non-iso endpoints */
> if (!is_out)
> allowed |= URB_SHORT_NOT_OK;
> Index: usb-4.x/drivers/usb/host/uhci-q.c
> ===================================================================
> --- usb-4.x.orig/drivers/usb/host/uhci-q.c
> +++ usb-4.x/drivers/usb/host/uhci-q.c
> @@ -73,8 +73,7 @@ static void uhci_add_fsbr(struct uhci_hc
> {
> struct urb_priv *urbp = urb->hcpriv;
>
> - if (!(urb->transfer_flags & URB_NO_FSBR))
> - urbp->fsbr = 1;
> + urbp->fsbr = 1;
So essentially fsbr gets set always. URB_NO_FSBR has no effect.
> }
>
> static void uhci_urbp_wants_fsbr(struct uhci_hcd *uhci, struct urb_priv *urbp)
> Index: usb-4.x/drivers/usb/usbip/stub_rx.c
> ===================================================================
> --- usb-4.x.orig/drivers/usb/usbip/stub_rx.c
> +++ usb-4.x/drivers/usb/usbip/stub_rx.c
> @@ -412,9 +412,6 @@ static void masking_bogus_flags(struct u
> if (is_out)
> allowed |= URB_ZERO_PACKET;
> /* FALLTHROUGH */
> - case USB_ENDPOINT_XFER_CONTROL:
> - allowed |= URB_NO_FSBR; /* only affects UHCI */
> - /* FALLTHROUGH */
usbip doesn't really do anything special for URB_NO_FSBR, other
than just setting the flag here. This is followed by usb_submit_urb().
Probably there is no need to set URB_NO_FSBR in USBIP to begin with,
considering usb_submit_urb() handled that before this patch.
I think it is safe to make the change.
Acked-by: Shuah Khan <shuahkh@xxxxxxxxxxxxxxx>
thanks,
-- Shuah
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