From: Johan Hovold <johan@kernel.org>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Greg KH <greg@kroah.com>,
Roger Whittaker <Roger.Whittaker@suse.com>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Takashi Iwai <tiwai@suse.de>, Johan Hovold <johan@kernel.org>,
USB list <linux-usb@vger.kernel.org>
Subject: Re: [PATCH] USB: Fix: Don't skip endpoint descriptors with maxpacket=0
Date: Mon, 6 Jan 2020 17:03:15 +0100 [thread overview]
Message-ID: <20200106160315.GA30908@localhost> (raw)
In-Reply-To: <Pine.LNX.4.44L0.2001061040270.1514-100000@iolanthe.rowland.org>
On Mon, Jan 06, 2020 at 10:43:42AM -0500, Alan Stern wrote:
> It turns out that even though endpoints with a maxpacket length of 0
> aren't useful for data transfer, the descriptors do serve other
> purposes. In particular, skipping them will also skip over other
> class-specific descriptors for classes such as UVC. This unexpected
> side effect has caused some UVC cameras to stop working.
>
> In addition, the USB spec requires that when isochronous endpoint
> descriptors are present in an interface's altsetting 0 (which is true
> on some devices), the maxpacket size _must_ be set to 0. Warning
> about such things seems like a bad idea.
>
> This patch updates an earlier commit which would log a warning and
> skip these endpoint descriptors. Now we only log a warning, and we
> don't even do that for isochronous endpoints in altsetting 0.
>
> We don't need to worry about preventing endpoints with maxpacket = 0
> from ever being used for data transfers; usb_submit_urb() already
> checks for this.
>
> Reported-and-tested-by: Roger Whittaker <Roger.Whittaker@suse.com>
> Fixes: d482c7bb0541 ("USB: Skip endpoints with 0 maxpacket length")
> Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
> CC: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Link: https://marc.info/?l=linux-usb&m=157790377329882&w=2
Acked-by: Johan Hovold <johan@kernel.org>
We also need
Cc: stable <stable@vger.kernel.org>
as d482c7bb0541 ("USB: Skip endpoints with 0 maxpacket length") ended up
being (auto- ?) selected for stable.
Johan
next prev parent reply other threads:[~2020-01-06 16:03 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200101144709.GA8389@suse.com>
[not found] ` <20200101172449.GF6226@pendragon.ideasonboard.com>
[not found] ` <20200101175220.GA18140@suse.com>
2020-01-01 18:35 ` Certain cameras no longer working with uvcvideo on recent (openSUSE) kernels Laurent Pinchart
2020-01-01 18:47 ` Greg KH
2020-01-01 20:09 ` Alan Stern
2020-01-02 11:20 ` Johan Hovold
2020-01-02 13:11 ` Takashi Iwai
2020-01-02 15:06 ` Alan Stern
2020-01-02 15:32 ` Johan Hovold
2020-01-02 18:24 ` Alan Stern
2020-01-02 16:38 ` Laurent Pinchart
2020-01-02 16:57 ` Roger Whittaker
2020-01-02 17:03 ` Laurent Pinchart
2020-01-02 17:49 ` Alan Stern
2020-01-02 21:51 ` Roger Whittaker
2020-01-02 23:11 ` Laurent Pinchart
2020-01-03 15:13 ` Alan Stern
2020-01-04 18:22 ` Laurent Pinchart
2020-01-05 12:28 ` Roger Whittaker
2020-01-06 15:43 ` [PATCH] USB: Fix: Don't skip endpoint descriptors with maxpacket=0 Alan Stern
2020-01-06 16:03 ` Johan Hovold [this message]
2020-01-06 16:17 ` Alan Stern
2020-01-06 19:12 ` Greg KH
2020-01-06 16:13 ` Laurent Pinchart
2020-01-06 16:21 ` Alan Stern
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