Re: [PATCH 7/7] USB: cdc-acm: always claim data interface

From: Johan Hovold <johan@kernel.org>
To: Oliver Neukum <oneukum@suse.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 7/7] USB: cdc-acm: always claim data interface
Date: Mon, 22 Mar 2021 15:13:42 +0100	[thread overview]
Message-ID: <YFimFgUnc2VVQbNx@hovoldconsulting.com> (raw)
In-Reply-To: <9a802d1120a03e34d0e40e1d4e1e558c5359e92b.camel@suse.com>

On Mon, Mar 22, 2021 at 11:46:47AM +0100, Oliver Neukum wrote:
> Am Donnerstag, den 18.03.2021, 16:52 +0100 schrieb Johan Hovold:
> > Make sure to always claim the data interface and bail out if it's
> > already bound to another driver or isn't authorised.
> 
> Hi,
> 
> Thanks for the fixes. All previous ones are good work.
> this one is problematic I am afraid.
> 
> 
> acm_probe() has a test for the availability of the interface:
> 
> 	if (!combined_interfaces && usb_interface_claimed(data_interface)) {
> 		/* valid in this context */
> 		dev_dbg(&intf->dev, "The data interface isn't available\n");
> 		return -EBUSY;
> 	}
> 
> That check is ancient. BKL still existed. If you want to remove it
> and do proper error handling, that would be good. But if you do
> error handling, the check has to go, too.

Thanks, this bit can go indeed. But note that it's simply because it's
now redundant.

I'll send a v2.

Johan