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 CF9C5C433EF for ; Thu, 31 Mar 2022 15:42:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233883AbiCaPoN (ORCPT ); Thu, 31 Mar 2022 11:44:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239249AbiCaPmh (ORCPT ); Thu, 31 Mar 2022 11:42:37 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C8A2ECC50D; Thu, 31 Mar 2022 08:37:30 -0700 (PDT) Received: from relay2.suse.de (relay2.suse.de [149.44.160.134]) by smtp-out1.suse.de (Postfix) with ESMTP id 907EB21A91; Thu, 31 Mar 2022 15:37:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1648741029; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=3q4Q3czP9jG+0ZzNk/gMKAVSAtyh28B5UBKgvoBIY/0=; b=YX4gWmmarEQZ6iyPydDBD4moCXu2qPhWbyKuFFU1S9OjYsyCGzolYDsGQi4bCJA5J6ClKW 42UYAcBR7+9LHffKBZ8J7mqX6MPcQ9IfbYsqJQycN0B60UqHKhug9PzhX2z6hRXIti2UO3 htYwAV7BRBuYOmAkxec2KAaIy08rvno= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1648741029; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=3q4Q3czP9jG+0ZzNk/gMKAVSAtyh28B5UBKgvoBIY/0=; b=rjcP2d81heangOxou0+niDIDB6s2GYYrq0ixfz0Gx+r+IWFbOheA69cHf8NV8Zkw31VGjN QghdKQ+usQIdQ4Bw== Received: from alsa1.suse.de (alsa1.suse.de [10.160.4.42]) by relay2.suse.de (Postfix) with ESMTP id 6EC0DA3B93; Thu, 31 Mar 2022 15:37:09 +0000 (UTC) Date: Thu, 31 Mar 2022 17:37:09 +0200 Message-ID: From: Takashi Iwai To: Benson Leung Cc: Takashi Iwai , Heikki Krogerus , 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 In-Reply-To: References: <20220330211913.2068108-1-wonchung@google.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/25.3 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Thu, 31 Mar 2022 17:33:03 +0200, Benson Leung wrote: > > 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. > > > > > > Takashi > > > > --- 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; > > > > If I recall this bug correctly, it's not the usb port perse that is falling > through this !dev_is_pci(dev) check, it's actually the usb4-port in a new > proposed patch by Heikki and Mika to extend the usb type-c component to > encompass the usb4 specific pieces too. Is it possible usb4 ports are considered > pci devices, and that's how we got into this situation? Yes, that explains for one of two changes in the original patch. But why data==NULL check is needed is still unclear. > Also, a little more background information: This crash happens because in > our kernel configs, we config'd the usb4 driver as =y (built in) instead of > =m module, which meant that the usb4 port's driver was adding a component > likely much earlier than hdac_i915. Thanks, it's what I supposed, too. Takashi