From: Johan Hovold <johan@kernel.org>
To: Oliver Neukum <oneukum@suse.com>
Cc: Johan Hovold <johan@kernel.org>, Erik Slagter <erik@slagter.name>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-usb@vger.kernel.org,
Daniel Caujolle-Bert <f1rmb.daniel@gmail.com>
Subject: Re: [PATCH v2 4/4] USB: cdc-acm: clean up no-union-descriptor handling
Date: Mon, 21 Sep 2020 17:16:05 +0200 [thread overview]
Message-ID: <20200921151605.GY24441@localhost> (raw)
In-Reply-To: <1600700674.2424.105.camel@suse.com>
On Mon, Sep 21, 2020 at 05:04:34PM +0200, Oliver Neukum wrote:
> Am Montag, den 21.09.2020, 16:28 +0200 schrieb Johan Hovold:
> > On Mon, Sep 21, 2020 at 04:16:56PM +0200, Oliver Neukum wrote:
> > > Am Montag, den 21.09.2020, 15:59 +0200 schrieb Johan Hovold:
> > > > For interfaces that lack a union descriptor, probe for a
> > > > "combined-interface" before falling back to the call-management
> > > > descriptor instead of the other way round.
> > >
> > > Hi,
>
> Hi,
>
> > >
> > > the more I look at this the more it seems to me like the
> > > device that has the quirk does NOT have a collapsed interface
> > > but two interfaces and just a lack of a union descriptor.
> >
> > But then why name the quirk NO_DATA_INTERFACE if it has a data
>
> In hindsight that seems not the best name.
>
> > interface? By hardcoding the data-interface number to be the one and
> > only interface, you'd end up probing for a "combined" interface also
> > with a broken call-management descriptor.
>
> Well, by the changelog assuming a combined interface caused an oops.
> Thence I am forced to conclude that the davices _has_ a separate
> data interface, but no union descriptor.
No, the oops was probably due to the missing sanity check later added by
403dff4e2c94 ("USB: cdc-acm: check for valid interfaces").
With a broken call-management descriptor pointing to a non-existent
interface we'd oops before that commit.
> > Side note: I really think we should start mandating lsusb output to go
> > along with any patch for quirky devices.
>
> Good idea. Convince Greg.
Heh. I'm sure he can be convinced. :)
Johan
next prev parent reply other threads:[~2020-09-21 15:16 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-21 13:59 [PATCH v2 0/4] USB: cdc-acm: handle broken union descriptors Johan Hovold
2020-09-21 13:59 ` [PATCH v2 1/4] Revert "cdc-acm: hardening against malicious devices" Johan Hovold
2020-09-21 13:59 ` [PATCH v2 2/4] USB: cdc-acm: handle broken union descriptors Johan Hovold
2020-09-22 9:53 ` <Daniel Caujolle-Bert>
2020-09-21 13:59 ` [PATCH v2 3/4] USB: cdc-acm: use common data-class define Johan Hovold
2020-09-21 13:59 ` [PATCH v2 4/4] USB: cdc-acm: clean up no-union-descriptor handling Johan Hovold
2020-09-21 14:16 ` Oliver Neukum
2020-09-21 14:28 ` Johan Hovold
2020-09-21 15:04 ` Oliver Neukum
2020-09-21 15:16 ` Johan Hovold [this message]
2020-09-21 17:17 ` Oliver Neukum
2020-09-22 7:05 ` Johan Hovold
2020-09-22 10:40 ` Oliver Neukum
2020-09-22 10:54 ` Johan Hovold
2020-09-22 11:41 ` Oliver Neukum
2020-09-22 11:47 ` Johan Hovold
2020-09-21 14:21 ` [PATCH v2 0/4] USB: cdc-acm: handle broken union descriptors <Daniel Caujolle-Bert>
2020-09-21 16:19 ` <Daniel Caujolle-Bert>
2020-09-22 7:08 ` Johan Hovold
2020-09-22 9:56 ` <Daniel Caujolle-Bert>
2020-09-22 10:07 ` Johan Hovold
2020-09-22 12:10 ` Oliver Neukum
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