Messages in this thread | | | Date | Fri, 20 Mar 2009 08:19:56 +0900 | From | Kenji Kaneshige <> | Subject | Re: [PATCH v4 08/12] PCI: Introduce /sys/bus/pci/devices/.../remove |
| |
Alex Chiang wrote: > * Kenji Kaneshige <kaneshige.kenji@jp.fujitsu.com>: >> 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 <xyzzy@speakeasy.org> >>> Signed-off-by: Alex Chiang <achiang@hp.com> >>> --- >>> >>> 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 <linux-pci@vger.kernel.org> >>> +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 <bhutchings@solarflare.com> >>> 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. >
Do you mean user removes bridge device to remove its *primary* bus? It is very strange. I think the bus should be removed when its parent bridge is removed.
> In other words, without it, we will still see the bus in: > > /sys/class/pci_bus/... >
What is the problem?
> 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. >
I think we don't need the two lines. But if you do that, you need list_empty(&pdev->bus->devices), doesn't it? On the other hand, we must not check 'bridge' in the if statement. Or bus will never be removed when non-bridge device is removed last on the bus.
Again, I think we don't need the two lines. But am I misunderstanding something?
Thanks, Kenji Kaneshige
> 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-pci" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > >
| |