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Subject[PATCH 8/8 v4] PCI: document the changes
Create how-to for SR-IOV user and device driver developer.

Signed-off-by: Yu Zhao <yu.zhao@intel.com>

---
Documentation/DocBook/kernel-api.tmpl | 1 +
Documentation/PCI/pci-iov-howto.txt | 222 +++++++++++++++++++++++++++++++++
2 files changed, 223 insertions(+), 0 deletions(-)
create mode 100644 Documentation/PCI/pci-iov-howto.txt
diff --git a/Documentation/DocBook/kernel-api.tmpl b/Documentation/DocBook/kernel-api.tmpl
index b7b1482..5cb6491 100644
--- a/Documentation/DocBook/kernel-api.tmpl
+++ b/Documentation/DocBook/kernel-api.tmpl
@@ -251,6 +251,7 @@ X!Edrivers/pci/hotplug.c
-->
!Edrivers/pci/probe.c
!Edrivers/pci/rom.c
+!Edrivers/pci/iov.c
</sect1>
<sect1><title>PCI Hotplug Support Library</title>
!Edrivers/pci/hotplug/pci_hotplug_core.c
diff --git a/Documentation/PCI/pci-iov-howto.txt b/Documentation/PCI/pci-iov-howto.txt
new file mode 100644
index 0000000..15d846d
--- /dev/null
+++ b/Documentation/PCI/pci-iov-howto.txt
@@ -0,0 +1,222 @@
+ PCI Express Single Root I/O Virtualization HOWTO
+ Copyright (C) 2008 Intel Corporation
+
+
+1. Overview
+
+1.1 What is SR-IOV
+
+Single Root I/O Virtualization (SR-IOV) is a PCI Express Extended
+capability which makes one physical device appear as multiple virtual
+devices. The physical device is referred to as Physical Function while
+the virtual devices are referred to as Virtual Functions. Allocation
+of Virtual Functions can be dynamically controlled by Physical Function
+via registers encapsulated in the capability. By default, this feature
+is not enabled and the Physical Function behaves as traditional PCIe
+device. Once it's turned on, each Virtual Function's PCI configuration
+space can be accessed by its own Bus, Device and Function Number (Routing
+ID). And each Virtual Function also has PCI Memory Space, which is used
+to map its register set. Virtual Function device driver operates on the
+register set so it can be functional and appear as a real existing PCI
+device.
+
+2. User Guide
+
+2.1 How can I manage SR-IOV
+
+If a device supports SR-IOV, then there should be some entries under
+Physical Function's PCI device directory. These entries are in directory:
+ - /sys/bus/pci/devices/XXXX:BB:DD.F/iov/
+ (XXXX:BB:DD:F is domain:bus:dev:fun)
+and
+ - /sys/bus/pci/devices/XXXX:BB:DD.F/iov/N
+ (N is VF number from 0 to initialvfs-1)
+
+To enable or disable SR-IOV:
+ - /sys/bus/pci/devices/XXXX:BB:DD.F/iov/enable
+ (writing 1/0 means enable/disable VFs, state change will
+ notify PF driver)
+
+To change number of Virtual Functions:
+ - /sys/bus/pci/devices/XXXX:BB:DD.F/iov/numvfs
+ (writing positive integer to this file will change NumVFs)
+
+The total and initial number of VFs can get from:
+ - /sys/bus/pci/devices/XXXX:BB:DD.F/iov/totalvfs
+ - /sys/bus/pci/devices/XXXX:BB:DD.F/iov/initialvfs
+
+The identifier of a VF that belongs to this PF can get from:
+ - /sys/bus/pci/devices/XXXX:BB:DD.F/iov/N/rid
+
+2.2 How can I use Virtual Functions
+
+Virtual Functions are treated as hot-plugged PCI devices in the kernel,
+so they should be able to work in the same way as real PCI devices.
+NOTE: Virtual Function device driver must be loaded to make it work.
+
+
+3. Developer Guide
+
+3.1 SR-IOV APIs
+
+To register SR-IOV service, Physical Function device driver needs to call:
+ int pci_iov_register(struct pci_dev *dev,
+ int (*notify)(struct pci_dev *, u32), char **entries)
+ The 'notify' is a callback function that the SR-IOV code will invoke
+ it when events related to VFs happen (e.g. user read/write the sysfs
+ entries). The first argument is PF itself, the second argument is
+ event type and value. For now, following events type are supported:
+ - PCI_IOV_ENABLE: SR-IOV enable request
+ - PCI_IOV_DISABLE: SR-IOV disable request
+ - PCI_IOV_RD_CONF: read configuration
+ - PCI_IOV_WR_CONF: write configuration
+ - PCI_IOV_POST_EVENT: post event
+ And event values can be extract using following masks:
+ - PCI_IOV_VIRTFN_ID: Virtual Function Number
+ - PCI_IOV_NUM_VIRTFN: num of Virtual Functions
+ - PCI_IOV_EVENT_TYPE: event type (pre/post)
+ The 'entries' is is a list of sysfs entry names that will be to
+ created by the SR-IOV code.
+
+Note: entries could be NULL if PF driver doesn't want to create new entries
+under /sys/bus/pci/devices/XXXX:BB:DD.F/iov/N/.
+
+To unregister SR-IOV service, Physical Function device driver needs to call:
+ void pci_iov_unregister(struct pci_dev *dev)
+
+To enable SR-IOV, Physical Function device driver needs to call:
+ int pci_iov_enable(struct pci_dev *dev, int numvfs)
+ 'numvfs' is the number of VFs that PF wants to enable.
+
+To disable SR-IOV, Physical Function device driver needs to call:
+ void pci_iov_disable(struct pci_dev *dev)
+
+Note: above two functions sleeps 1 second waiting on hardware transaction
+completion according to SR-IOV specification.
+
+To read or write VFs configuration:
+ - int pci_iov_read_config(struct pci_dev *dev, int vfn,
+ char *entry, char *buf, int size);
+ - int pci_iov_write_config(struct pci_dev *dev, int vfn,
+ char *entry, char *buf);
+3.2 Usage example
+
+Following piece of code illustrates the usage of APIs above.
+
+static char *entries[] = { "foo", "bar", NULL };
+
+static int callback(struct pci_dev *dev, u32 event)
+{
+ int err;
+ int vfn;
+ int numvfs;
+
+ if (event & PCI_IOV_ENABLE) {
+ /*
+ * request to enable SR-IOV, NumVFs is available.
+ * Note: if the PF want to support PM, it has to
+ * check the device power state here to see if
+ * the request is allowed or not.
+ */
+
+ numvfs = event & PCI_IOV_NUM_VIRTFN;
+
+ } else if (event & PCI_IOV_DISABLE) {
+ /*
+ * request to disable SR-IOV.
+ */
+ ...
+
+ } else if (event & PCI_IOV_RD_CONF) {
+ /*
+ * request to read VF configuration, Virtual
+ * Function Number is available.
+ */
+
+ vfn = event & PCI_IOV_VIRTFN_ID;
+
+ /* pass the config to SR-IOV code so user can read it */
+ err = pci_iov_write_config(dev, vfn, entry, buf);
+
+ } else if (event & PCI_IOV_WR_CONF) {
+ /*
+ * request to write VF configuration, Virtual
+ * Function Number is available.
+ */
+
+ vfn = event & PCI_IOV_VIRTFN_ID;
+
+ /* read the config that has been written by user */
+ err = pci_iov_read_config(dev, vfn, entry, buf, size);
+
+ } else
+ return -EINVAL;
+
+ return err;
+}
+
+static int __devinit dev_probe(struct pci_dev *dev,
+ const struct pci_device_id *id)
+{
+ int err;
+
+ err = pci_iov_register(dev, callback, entries);
+ ...
+
+ err = pci_iov_enable(dev, nr_virtfn, callback);
+
+ ...
+
+ return err;
+}
+
+static void __devexit dev_remove(struct pci_dev *dev)
+{
+ ...
+
+ pci_iov_disable(dev);
+
+ ...
+
+ pci_iov_unregister(dev);
+
+ ...
+}
+
+#ifdef CONFIG_PM
+/*
+ * If Physical Function supports the power management, then the
+ * SR-IOV needs to be disabled before the adapter goes to sleep,
+ * because Virtual Functions will not work when the adapter is in
+ * the power-saving mode.
+ * The SR-IOV can be enabled again after the adapter wakes up.
+ */
+static int dev_suspend(struct pci_dev *dev, pm_message_t state)
+{
+ ...
+
+ pci_iov_disable(dev);
+
+ ...
+}
+
+static int dev_resume(struct pci_dev *dev)
+{
+ ...
+
+ pci_iov_enable(dev, numvfs);
+
+ ...
+}
+#endif
+
+static struct pci_driver dev_driver = {
+ .name = "SR-IOV Physical Function driver",
+ .id_table = dev_id_table,
+ .probe = dev_probe,
+ .remove = __devexit_p(dev_remove),
+#ifdef CONFIG_PM
+ .suspend = dev_suspend,
+ .resume = dev_resume,
+#endif
+};
--
1.5.6.4


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