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

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Message-ID: <YFimFgUnc2VVQbNx@hovoldconsulting.com>
Date:   Mon, 22 Mar 2021 15:13:42 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Oliver Neukum <oneukum@...e.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/7] USB: cdc-acm: always claim data interface

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