From: Juergen Gross <jgross@suse.com>
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: xen-devel@lists.xensource.com, stefano.stabellini@eu.citrix.com
Subject: Re: [Patch RFC 2/4] usb: add flag to USBPacket to request complete callback after isoc transfer
Date: Fri, 17 Jul 2015 10:44:45 +0200 [thread overview]
Message-ID: <55A8C07D.1010306@suse.com> (raw)
In-Reply-To: <1437120751.3689.14.camel@redhat.com>
On 07/17/2015 10:12 AM, Gerd Hoffmann wrote:
> On Do, 2015-07-16 at 17:47 +0200, Juergen Gross wrote:
>> In order to avoid having to poll for the result of an iso transfer
>> add the possibility to request the "complete" callback which is being
>> used for bulk transfers as well.
>
> Sorry for the late notice (didn't do much usb coding recently and forgot
> about it): We actually _have_ a notification mechanism already:
> usb_wakeup(USBEndpoint *ep, int streamid). That will trigger a
> USBPortOps->wakeup callback in the host adapter emulation.
>
> So, the usb-host change should be as simple as this:
>
> --- a/hw/usb/host-libusb.c
> +++ b/hw/usb/host-libusb.c
> @@ -451,6 +451,7 @@ static void usb_host_req_complete_iso(struct
> libusb_transfer *transfer)
> }
> if (xfer->ring->ep->pid == USB_TOKEN_IN) {
> QTAILQ_INSERT_TAIL(&xfer->ring->copy, xfer, next);
> + usb_wakeup(xfer->ring->ep, 0);
> } else {
> QTAILQ_INSERT_TAIL(&xfer->ring->unused, xfer, next);
> }
Hmm, I can see the benefit of this call to avoid polling.
OTOH I don't see how to find the packages already processed via this
mechanism. To help in my case I'd need:
- the call being made in the else clause
- some way to have a package reference in the endpoint (assuming
to use the bus .endpoint_wakeup callback which is called by
usb_wakeup(), too).
The problem here is that host-libusb.c would call usb_wakeup()
not for each packet, but for each libusb I/O, which is combining
multiple packets given to usb_handle_packet().
Juergen
next prev parent reply other threads:[~2015-07-17 8:44 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-16 15:47 [Patch RFC 0/4] usb, xen: add pvUSB backend Juergen Gross
2015-07-16 15:47 ` [Patch RFC 1/4] usb: support device specification via <bus>-<port> Juergen Gross
2015-07-17 6:59 ` Gerd Hoffmann
2015-07-17 7:32 ` Juergen Gross
2015-07-17 8:28 ` Gerd Hoffmann
2015-07-17 10:06 ` Juergen Gross
2015-07-17 10:23 ` Gerd Hoffmann
2015-07-17 10:25 ` Juergen Gross
2015-07-16 15:47 ` [Patch RFC 2/4] usb: add flag to USBPacket to request complete callback after isoc transfer Juergen Gross
2015-07-17 8:12 ` Gerd Hoffmann
2015-07-17 8:44 ` Juergen Gross [this message]
2015-07-17 9:23 ` Gerd Hoffmann
2015-07-17 10:14 ` Juergen Gross
2015-07-16 15:47 ` [Patch RFC 3/4] xen: introduce dummy system device Juergen Gross
2015-07-16 15:47 ` [Patch RFC 4/4] xen: add pvUSB backend Juergen Gross
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