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SubjectRe: [PATCH v3 07/11] PCI: Introduce /sys/bus/pci/devices/.../remove
* Alex Chiang <achiang@hp.com>:
> * Alex Chiang <achiang@hp.com>:
> > This is an updated version of this patch. It fixes a bug where we
> > would remove a bridge even if it still had children.
> >
> > Now we check for children before attempting to remove the bridge.
>
> This is another updated version of the patch.
>
> It adds a mutex for the sysfs callback function.

Yet another updated version. Removes an extra pci_dev_put that
was causing us to reference the pci_dev after it was freed
(which showed up when slab poisoning debugging was turned on).

This iteration plus the sysfs rfc patch I posted earlier today
survives Vegard's test cases.

http://lkml.org/lkml/2009/3/10/476

Need to try and test the entire series under under kmemcheck once
I figure out how to do that.

Thanks.

/ac

commit 22222eefb1535eca972e60f60e6a44bbada6bd35
Author: Alex Chiang <achiang@hp.com>
Date: Tue Mar 10 22:01:32 2009 -0600

PCI: Introduce /sys/bus/pci/devices/.../remove

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.

Cc: djwong@us.ibm.com
Cc: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Alex Chiang <achiang@hp.com>

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 a29fc3b..b276fa2 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -219,6 +219,50 @@ msi_bus_store(struct device *dev, struct device_attribute *attr,
return count;
}

+#ifdef CONFIG_HOTPLUG
+static DEFINE_MUTEX(pci_remove_mutex);
+static void remove_callback(struct device *dev)
+{
+ int bridge = 0;
+ struct pci_dev *pdev = to_pci_dev(dev);
+
+ mutex_lock(&pci_remove_mutex);
+
+ if (pdev->subordinate)
+ bridge = 1;
+
+ pci_remove_bus_device(pdev);
+ if (bridge && list_empty(&pdev->bus->devices))
+ pci_remove_bus(pdev->bus);
+
+ mutex_unlock(&pci_remove_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[] = {
__ATTR_RO(resource),
__ATTR_RO(vendor),
@@ -237,6 +281,9 @@ 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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