Alex Chiang wrote:
* Kenji Kaneshige <kaneshige.kenji@xxxxxxxxxxxxxx>:
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@xxxxxxxxxxxxx>
Signed-off-by: Alex Chiang <achiang@xxxxxx>
---
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@xxxxxxxxxxxxxxx>
+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@xxxxxxxxxxxxxx>
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,
};
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