Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759383AbZCSQld (ORCPT ); Thu, 19 Mar 2009 12:41:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753432AbZCSQlX (ORCPT ); Thu, 19 Mar 2009 12:41:23 -0400 Received: from g5t0008.atlanta.hp.com ([15.192.0.45]:26354 "EHLO g5t0008.atlanta.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751880AbZCSQlW (ORCPT ); Thu, 19 Mar 2009 12:41:22 -0400 Date: Thu, 19 Mar 2009 10:41:19 -0600 From: Alex Chiang To: Kenji Kaneshige Cc: jbarnes@virtuousgeek.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Trent Piepho Subject: Re: [PATCH v4 08/12] PCI: Introduce /sys/bus/pci/devices/.../remove Message-ID: <20090319164119.GC8074@ldl.fc.hp.com> References: <20090318222426.887.1008.stgit@bob.kio> <20090318224006.887.91805.stgit@bob.kio> <49C2540E.70207@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <49C2540E.70207@jp.fujitsu.com> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6508 Lines: 183 * Kenji Kaneshige : > Alex Chiang wrote: >> This patch adds an attribute named "remove" to a PCI device's sysfs >> directory. Writing a non-zero value to this attribute will remove the PCI >> device and any children of it. >> >> Trent Piepho wrote the original implementation and documentation. >> >> Thanks to Vegard Nossum for testing under kmemcheck and finding locking >> issues with the sysfs interface. >> >> Cc: Trent Piepho >> Signed-off-by: Alex Chiang >> --- >> >> Documentation/ABI/testing/sysfs-bus-pci | 8 ++++++ >> Documentation/filesystems/sysfs-pci.txt | 10 +++++++ >> drivers/pci/pci-sysfs.c | 44 +++++++++++++++++++++++++++++++ >> 3 files changed, 62 insertions(+), 0 deletions(-) >> >> diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci >> index ea4aee2..5b1ddde 100644 >> --- a/Documentation/ABI/testing/sysfs-bus-pci >> +++ b/Documentation/ABI/testing/sysfs-bus-pci >> @@ -50,6 +50,14 @@ Description: >> re-discover previously removed devices. >> Depends on CONFIG_HOTPLUG. >> +What: /sys/bus/pci/devices/.../remove >> +Date: January 2009 >> +Contact: Linux PCI developers >> +Description: >> + Writing a non-zero value to this attribute will >> + hot-remove the PCI device and any of its children. >> + Depends on CONFIG_HOTPLUG. >> + >> What: /sys/bus/pci/devices/.../vpd >> Date: February 2008 >> Contact: Ben Hutchings >> diff --git a/Documentation/filesystems/sysfs-pci.txt b/Documentation/filesystems/sysfs-pci.txt >> index 9f8740c..26e4b8b 100644 >> --- a/Documentation/filesystems/sysfs-pci.txt >> +++ b/Documentation/filesystems/sysfs-pci.txt >> @@ -12,6 +12,7 @@ that support it. For example, a given bus might look like this: >> | |-- enable >> | |-- irq >> | |-- local_cpus >> + | |-- remove >> | |-- resource >> | |-- resource0 >> | |-- resource1 >> @@ -36,6 +37,7 @@ files, each with their own function. >> enable Whether the device is enabled (ascii, rw) >> irq IRQ number (ascii, ro) >> local_cpus nearby CPU mask (cpumask, ro) >> + remove remove device from kernel's list (ascii, wo) >> resource PCI resource host addresses (ascii, ro) >> resource0..N PCI resource N, if present (binary, mmap) >> resource0_wc..N_wc PCI WC map resource N, if prefetchable (binary, mmap) >> @@ -46,6 +48,7 @@ files, each with their own function. >> ro - read only file >> rw - file is readable and writable >> + wo - write only file >> mmap - file is mmapable >> ascii - file contains ascii text >> binary - file contains binary data >> @@ -73,6 +76,13 @@ that the device must be enabled for a rom read to return data succesfully. >> In the event a driver is not bound to the device, it can be enabled using the >> 'enable' file, documented above. >> +The 'remove' file is used to remove the PCI device, by writing a >> non-zero >> +integer to the file. This does not involve any kind of hot-plug functionality, >> +e.g. powering off the device. The device is removed from the kernel's list of >> +PCI devices, the sysfs directory for it is removed, and the device will be >> +removed from any drivers attached to it. Removal of PCI root buses is >> +disallowed. >> + >> Accessing legacy resources through sysfs >> ---------------------------------------- >> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c >> index 22dbc65..6e2b1fd 100644 >> --- a/drivers/pci/pci-sysfs.c >> +++ b/drivers/pci/pci-sysfs.c >> @@ -246,6 +246,47 @@ struct bus_attribute pci_bus_attrs[] = { >> __ATTR(rescan, S_IWUSR, NULL, bus_rescan_store), >> __ATTR_NULL >> }; >> + >> +static void remove_callback(struct device *dev) >> +{ >> + int bridge = 0; >> + struct pci_dev *pdev = to_pci_dev(dev); >> + >> + mutex_lock(&pci_remove_rescan_mutex); >> + >> + if (pdev->subordinate) >> + bridge = 1; >> + >> + pci_remove_bus_device(pdev); >> + if (bridge && list_empty(&pdev->bus->devices)) >> + pci_remove_bus(pdev->bus); > > I cannot understand the above two lines. Could you explain > what it intend? If the user says: echo 1 > /sys/bus/pci/devices/.../remove And that device is a bridge, then we need to specifically call pci_remove_bus as well, to actually remove the bus itself. Without it, pci_bus_remove_device() will remove all of its children (and subordinate buses) in a depth-first manner, but we will never actually remove the bus that the user specified. In other words, without it, we will still see the bus in: /sys/class/pci_bus/... We only want to remove the bus if it has no children left. I think the check for list_empty(&pdev->bus->devices) might be overkill... I can try taking that bit out and testing again. Thanks for the review. /ac > Thanks, > Kenji Kaneshige > > >> + >> + mutex_unlock(&pci_remove_rescan_mutex); >> +} >> + >> +static ssize_t >> +remove_store(struct device *dev, struct device_attribute *dummy, >> + const char *buf, size_t count) >> +{ >> + int ret = 0; >> + unsigned long val; >> + struct pci_dev *pdev = to_pci_dev(dev); >> + >> + if (strict_strtoul(buf, 0, &val) < 0) >> + return -EINVAL; >> + >> + if (!capable(CAP_SYS_ADMIN)) >> + return -EPERM; >> + >> + if (pdev->subordinate && pci_is_root_bus(pdev->bus)) >> + return -EBUSY; >> + >> + if (val) >> + ret = device_schedule_callback(dev, remove_callback); >> + if (ret) >> + count = ret; >> + return count; >> +} >> #endif >> struct device_attribute pci_dev_attrs[] = { >> @@ -266,6 +307,9 @@ struct device_attribute pci_dev_attrs[] = { >> __ATTR(broken_parity_status,(S_IRUGO|S_IWUSR), >> broken_parity_status_show,broken_parity_status_store), >> __ATTR(msi_bus, 0644, msi_bus_show, msi_bus_store), >> +#ifdef CONFIG_HOTPLUG >> + __ATTR(remove, S_IWUSR, NULL, remove_store), >> +#endif >> __ATTR_NULL, >> }; >> >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-pci" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> >> > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/