linux-kernel - Re: [PATCH] hso: fix handling of modem port SERIAL

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Date:	Mon, 06 Jan 2014 15:39:40 -0600
From:	Dan Williams <dcbw@...hat.com>
To:	David Miller <davem@...emloft.net>
Cc:	hns@...delico.com, j.dumon@...ion.com, linux-usb@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	marek.belisko@...il.com, e.verdonck@...ion.com
Subject: Re: [PATCH] hso: fix handling of modem port SERIAL_STATE
 notifications

On Mon, 2014-01-06 at 16:30 -0500, David Miller wrote:
> From: Dan Williams <dcbw@...hat.com>
> Date: Mon, 06 Jan 2014 10:07:29 -0600
> 
> > The existing serial state notification handling expected older Option
> > devices, having a hardcoded assumption that the Modem port was always
> > USB interface #2.  That isn't true for devices from the past few years.
> > 
> > hso_serial_state_notification is a local cache of a USB Communications
> > Interface Class SERIAL_STATE notification from the device, and the
> > USB CDC specification (section 6.3, table 67 "Class-Specific Notifications")
> > defines wIndex as the USB interface the event applies to.  For hso
> > devices this will always be the Modem port, as the Modem port is the
> > only port which is set up to receive them by the driver.
> > 
> > So instead of always expecting USB interface #2, instead validate the
> > notification with the actual USB interface number of the Modem port.
> > 
> > Signed-off-by: Dan Williams <dcbw@...hat.com>
> > Tested-by: H. Nikolaus Schaller <hns@...delico.com>
> 
> Applied, although that BUG_ON() is a bit harsh.  It might have been
> cleaner to just dev_warn() ratelimited or similar and return.

If the driver ever gets to that callback for any !Modem port, something
is horribly wrong, which the BUG_ON() was attempting to make explicit.
The driver only enables that callback for the Modem port, so yeah, it's
somewhat defensive.  I'm happy to send a fixup if you like?

Dan


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