From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D538DC433F5 for ; Thu, 31 Mar 2022 11:40:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235267AbiCaLlw (ORCPT ); Thu, 31 Mar 2022 07:41:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42130 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230433AbiCaLlr (ORCPT ); Thu, 31 Mar 2022 07:41:47 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E6FE727B1E; Thu, 31 Mar 2022 04:39:59 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id A3A63B81BE2; Thu, 31 Mar 2022 11:39:58 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C3DF9C340ED; Thu, 31 Mar 2022 11:39:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1648726797; bh=chTX46Ow2eQgl0OjiZhg3AwRDXcUJ7di937siRva6Uc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=UR5XzPsvt5NZkUoPPrzW3NsawOqugmV1MRmm5uraBPMD0XsKr97Ee9h0+uoiWebIt RRWfzxof4tUd/6hiyWMx5daNW62XwC4DAVWOl/Bn7Ei7kNEtsnDq6xdXMcRIgjE+qr Niyq9kD7P6sPh0UOJY/pMI5fakTflcraimJEOf0M= Date: Thu, 31 Mar 2022 13:39:51 +0200 From: Greg KH To: Heikki Krogerus Cc: Takashi Iwai , Won Chung , Jaroslav Kysela , Takashi Iwai , Mika Westerberg , Benson Leung , Prashant Malani , linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] sound/hda: Add NULL check to component match callback function Message-ID: References: <20220330211913.2068108-1-wonchung@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 31, 2022 at 12:25:43PM +0300, Heikki Krogerus wrote: > On Thu, Mar 31, 2022 at 11:12:55AM +0200, Takashi Iwai wrote: > > > > > - if (!strcmp(dev->driver->name, "i915") && > > > > > + if (dev->driver && !strcmp(dev->driver->name, "i915") && > > > > > > > > Can NULL dev->driver be really seen? I thought the components are > > > > added by the drivers, hence they ought to have the driver field set. > > > > But there can be corner cases I overlooked. > > > > > > > > > > > > thanks, > > > > > > > > Takashi > > > > > > Hi Takashi, > > > > > > When I try using component_add in a different driver (usb4 in my > > > case), I think dev->driver here is NULL because the i915 drivers do > > > not have their component master fully bound when this new component is > > > registered. When I test it, it seems to be causing a crash. > > > > Hm, from where component_add*() is called? Basically dev->driver must > > be already set before the corresponding driver gets bound at > > __driver_probe_deviec(). So, if the device is added to component from > > the corresponding driver's probe, dev->driver must be non-NULL. > > The code that declares a device as component does not have to be the > driver of that device. > > In our case the components are USB ports, and they are devices that > are actually never bind to any drivers: drivers/usb/core/port.c Why is a USB device being passed to this code that assumes it is looking for a PCI device with a specific driver name? As I mentioned on the mei patch, triggering off of a name is really a bad idea, as is assuming the device type without any assurance it is such a device (there's a reason we didn't provide device type identification in the driver core, don't abuse that please...) thanks, greg k-h