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 C4455C433F5 for ; Fri, 1 Apr 2022 07:02:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244808AbiDAHEY (ORCPT ); Fri, 1 Apr 2022 03:04:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54946 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236804AbiDAHEW (ORCPT ); Fri, 1 Apr 2022 03:04:22 -0400 Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C509321DF22; Fri, 1 Apr 2022 00:02:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1648796552; x=1680332552; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=nNoodzSci328///pz5PHrckfWv0oUcZ0OAexwl63MVM=; b=eOqWuqRyMBb9dbXNteW6+M0VA442DXXYoQhGJISHG9P9uWIQ9HKB2Cxj ++WTPfiehdmSuSgIYIhqyvRfb6+nfy9UKncUCaiK5N4RrebdW+hKC+PNt wBXpTPVT30Gsb8xbZi8I4uOUBpj7+qlzJvJLMdaZNkH/PccyGKdwCvnBI 2nnBWlhbiOxBFmzAvlOesWEJyp+qrco1IJZswr6oi+0E7gw8hrM8Wfjs6 b+DWJ2l7xCdZrIasivxwAho/ppkCHJPxhQceluN2FXIcFmDYQCXkqc2cI +KRJLc7M+Dfg2gUMYAJJzKl6H5rVHp3jYiKDabwb2jTTtxqu6Si9I3ACh w==; X-IronPort-AV: E=McAfee;i="6200,9189,10303"; a="259763359" X-IronPort-AV: E=Sophos;i="5.90,226,1643702400"; d="scan'208";a="259763359" Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Apr 2022 00:02:32 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.90,226,1643702400"; d="scan'208";a="695791642" Received: from kuha.fi.intel.com ([10.237.72.185]) by fmsmga001.fm.intel.com with SMTP; 01 Apr 2022 00:02:28 -0700 Received: by kuha.fi.intel.com (sSMTP sendmail emulation); Fri, 01 Apr 2022 10:02:27 +0300 Date: Fri, 1 Apr 2022 10:02:27 +0300 From: Heikki Krogerus To: Takashi Iwai Cc: 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: stable@vger.kernel.org Hi Takashi, On Thu, Mar 31, 2022 at 04:19:15PM +0200, Takashi Iwai wrote: > On Thu, 31 Mar 2022 15:29:10 +0200, > Takashi Iwai wrote: > > > > On Thu, 31 Mar 2022 11:45:47 +0200, > > Takashi Iwai wrote: > > > > > > On Thu, 31 Mar 2022 11:34:38 +0200, > > > Heikki Krogerus wrote: > > > > > > > > On Thu, Mar 31, 2022 at 11:28:20AM +0200, Takashi Iwai wrote: > > > > > On Thu, 31 Mar 2022 11:25:43 +0200, > > > > > 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 > > > > > > > > > > OK, that's what I wanted to know. It'd be helpful if it's more > > > > > clearly mentioned in the commit log. > > > > > > > > Agree. > > > > > > > > > BTW, the same problem must be seen in MEI drivers, too. > > > > > > > > Wasn't there a patch for those too? I lost track... > > > > > > I don't know, I just checked the latest Linus tree. > > > > > > And, looking at the HD-audio code, I still wonder how NULL dev->driver > > > can reach there. Is there any PCI device that is added to component > > > without binding to a driver? We have dev_is_pci() check at the > > > beginning, so non-PCI devices should bail out there... > > > > Further reading on, I'm really confused. How data=NULL can be passed > > to this function? The data argument is the value passed from the > > component_match_add_typed() call in HD-audio driver, hence it must be > > always the snd_hdac_bus object. > > > > And, I guess the i915 string check can be omitted completely, at > > least, for HD-audio driver. It already have a check of the parent of > > the device and that should be enough. > > That said, something like below (supposing data NULL check being > superfluous), instead. I don't think data can be NULL. There is no need for that check like you said. > --- a/sound/hda/hdac_i915.c > +++ b/sound/hda/hdac_i915.c > @@ -102,18 +102,13 @@ static int i915_component_master_match(struct device *dev, int subcomponent, > struct pci_dev *hdac_pci, *i915_pci; > struct hdac_bus *bus = data; > > - if (!dev_is_pci(dev)) > + if (subcomponent != I915_COMPONENT_AUDIO || !dev_is_pci(dev)) > return 0; > > hdac_pci = to_pci_dev(bus->dev); > i915_pci = to_pci_dev(dev); > > - if (!strcmp(dev->driver->name, "i915") && > - subcomponent == I915_COMPONENT_AUDIO && > - connectivity_check(i915_pci, hdac_pci)) > - return 1; > - > - return 0; > + return connectivity_check(i915_pci, hdac_pci); > } > > /* check whether intel graphics is present */ That looks really nice to me! thanks, -- heikki