From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bartlomiej Zolnierkiewicz Subject: Re: [PATCH 1/2] hpt366: fix PCI clock detection for HPT374 Date: Sat, 11 Aug 2007 18:41:34 +0200 Message-ID: <200708111841.34648.bzolnier@gmail.com> References: <200708060006.35511.sshtylyov@ru.mvista.com> <200708102354.21897.bzolnier@gmail.com> <46BDDDEF.9080001@ru.mvista.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from fk-out-0910.google.com ([209.85.128.187]:8699 "EHLO fk-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751433AbXHKQmB (ORCPT ); Sat, 11 Aug 2007 12:42:01 -0400 Received: by fk-out-0910.google.com with SMTP id z23so985112fkz for ; Sat, 11 Aug 2007 09:41:59 -0700 (PDT) In-Reply-To: <46BDDDEF.9080001@ru.mvista.com> Content-Disposition: inline Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Sergei Shtylyov Cc: Alan Cox , rah@bash.sh, linux-ide@vger.kernel.org On Saturday 11 August 2007, Sergei Shtylyov wrote: > Bartlomiej Zolnierkiewicz wrote: > > >>>>>>+ if (chip_type == HPT374 && (PCI_FUNC(dev->devfn) & 1)) { > >>>>>>+ struct pci_dev *dev1 = pci_get_slot(dev->bus, > >>>>>>+ dev->devfn - 1); > > >>>>>Can be NULL > > >>>> Not really. This may not be called if it's NULL -- see hpt374_init_setup(). > >>>>Maybe worth a comment though... > > >>>>>>+ unsigned long io_base = pci_resource_start(dev1, 4); > > >>>>>Kaboom > > >>>> That was a dud bomb. ;-) > > >>>What stops a hot unplug of a 374 from causing that to occur. I don't see > > >> Pinned as in pci_get_device()? If so, see setup-ide.c:ide_scan_pcibus(). > >>The IDE core does that for me. > > > ide_scan_pcibus() is used iff IDE is built-in. > > > Moreover pci_get_device() holds reference _only_ to the current PCI device > > (the reference count to @from PCI device is _always_ decremented). > > Indeed... doesn't it look like a buglet in the IDE core? It is OK, when ide_scan_pcibus() is not used probing is done by PCI layer and it keeps the reference to the PCI device in pci_device_probe(). > >>>where you have the other pci_dev pinned on a hotplug on a box set to scan > >>>the devices in reverse order > > >> Function 1 will always be skipped, regardless of the scan order. > > > Yes, but init_chipset_hpt366() will still try to access Function 1 > > No! Re-read the code please: init_chipset_hpt366() won't be called for > function 1 if that one is not detected, and only in this case it does function > 0 access to read the saved f_CNT value. Argh, thinko on my side. Unfortunately patch needs fixing anyway since the new comment is incorrect because the reference is kept by hpt366 driver itself - pci_get_slot() in init_setup_hpt374() - not the IDE core... Thanks, Bart