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Date: Thu, 19 Mar 2009 23:17:50 +0900
From: Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
To: Alex Chiang <achiang@...com>
CC: jbarnes@...tuousgeek.org, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org, Trent Piepho <xyzzy@...akeasy.org>
Subject: Re: [PATCH v4 08/12] PCI: Introduce /sys/bus/pci/devices/.../remove
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@...akeasy.org>
> Signed-off-by: Alex Chiang <achiang@...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@...r.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@...arflare.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?
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,
> };
>
>
> --
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>
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