From: Alan Stern <stern@rowland.harvard.edu>
To: Allen Blaylock <AllenB@epiloglaser.com>
Cc: Manu Gautam <mgautam@codeaurora.org>,
Peter Chen <peter.chen@nxp.com>,
"linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>
Subject: RE: EHSET with hub and PCIe root hub
Date: Thu, 12 Sep 2019 16:51:15 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.1909121648280.1305-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <BYAPR20MB2501A4FBEDBBC6353B6EC585CCB00@BYAPR20MB2501.namprd20.prod.outlook.com>
On Thu, 12 Sep 2019, Allen Blaylock wrote:
> >I should add that the USB 2.0 spec includes the following text (from section 11.24.2.13):
> >
> > Test mode of a downstream facing port can only be used in
> > a well defined sequence of hub states. This sequence is
> > defined as follows:
> >
> > 1) All enabled downstream facing ports of the hub containing
> > the port to be tested must be (selectively) suspended via
> > the SetPortFeature(PORT_SUSPEND) request. Each downstream
> > facing port of the hub must be in the disabled,
> > disconnected, or suspended state (see Figure 11-9).
> >
> >So you can see the hub probably failed the request because a non-suspended device was connected to port 3. (And who knows what was attached to the other ports -- the usbmon trace doesn't say.)
> >
> >Alan Stern
>
> This was very helpful.
>
> I was able to get the USB3503 to generate test packets by adding a SetPortFeature(PORT_SUSPEND) request to suspend the port before setting the PORT_TEST feature. Is there a way to tell that a device is a hub but not a root hub so ports on root hub ports aren't suspended prior to calling SetPortFeature(PORT_TEST)?
>
> I tried to use hub_udev->maxchild to determine if something was a hub but this appears misguided since root hubs can have multiple children, nothing else in the usb_device structure jumped out as being directly related to a hub.
That's a perfectly good way to see that the device really is a hub. In
addition, if hub_udev->parent == NULL then hub_udev is a root hub,
otherwise it isn't.
Alan Stern
next prev parent reply other threads:[~2019-09-12 20:51 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-10 22:01 EHSET with hub and PCIe root hub Allen Blaylock
2019-09-11 2:57 ` Peter Chen
2019-09-11 3:54 ` Manu Gautam
2019-09-11 20:34 ` Allen Blaylock
2019-09-12 0:49 ` Peter Chen
2019-09-12 14:20 ` Alan Stern
2019-09-12 14:28 ` Alan Stern
2019-09-12 20:32 ` Allen Blaylock
2019-09-12 20:51 ` Alan Stern [this message]
2019-09-16 1:11 ` Peter Chen
2019-09-12 14:29 ` Allen Blaylock
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