Message-ID: <1415355810.2671.18.camel@linux-0dmf.site>
Subject: Re: [PATCH] USB: cdc-acm: add quirk for control-line state requests
From: Oliver Neukum <oneukum@suse.de>
To: Johan Hovold <johan@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>, linux-usb@vger.kernel.org,
        Nix <nix@esperi.org.uk>, Paul Martin <pm@debian.org>,
        Daniel Silverstone <dsilvers@debian.org>, linux-kernel@vger.kernel.org,
        stable <stable@vger.kernel.org>
Date: Fri, 07 Nov 2014 11:23:30 +0100
In-Reply-To: <20141107091615.GC27326@localhost>
References: <20141106170456.GC26196@localhost>
	 <1415293713-3051-1-git-send-email-johan@kernel.org>
	 <1415351112.2671.9.camel@linux-0dmf.site>
	 <20141107091615.GC27326@localhost>
Content-Type: text/plain; charset="UTF-8"
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org

On Fri, 2014-11-07 at 10:16 +0100, Johan Hovold wrote:
> On Fri, Nov 07, 2014 at 10:05:12AM +0100, Oliver Neukum wrote:
> > On Thu, 2014-11-06 at 18:08 +0100, Johan Hovold wrote:
> > > Add new quirk for devices that cannot handle control-line state
> > > requests.
> > > 
> > > Note that we currently send these requests to all devices, regardless
> > > of
> > > whether they claim to support it, but that errors are only logged if
> > > support is claimed.
> > 
> > That makes me wonder whether we should do this. What do you think?
> 
> My interpretation was that it's done this way as there may be devices
> with broken CDC headers which fail to set the corresponding capability
> bits, but still support the request (c.f. our recent not-a-modem
> discussion).

Oh well, yes I don't like it, but we can't risk the change.

> In that case, always attempting the request, but only reporting errors
> if support was claimed, makes sense.
> 
> As changing this behaviour now would risk breaking such devices, I
> think black-listing (i.e. this patch) is preferred moving forward.

Unfortunately, yes.

	Regards
		Oliver


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/