From: Dave Ertman <david.m.ertman@xxxxxxxxx>
This is the initial implementation of the Virtual Bus,
virtbus_device and virtbus_driver. The virtual bus is
a software based bus intended to support lightweight
devices and drivers and provide matching between them
and probing of the registered drivers.
Files added:
drivers/bus/virtual_bus.c
include/linux/virtual_bus.h
Documentation/driver-api/virtual_bus.rst
The primary purpose of the virual bus is to provide
matching services and to pass the data pointer
contained in the virtbus_device to the virtbus_driver
during its probe call. This will allow two separate
kernel objects to match up and start communication.
The bus will support probe/remove shutdown and
suspend/resume callbacks.
Kconfig and Makefile alterations are included
Signed-off-by: Dave Ertman <david.m.ertman@xxxxxxxxx>
Signed-off-by: Kiran Patil <kiran.patil@xxxxxxxxx>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@xxxxxxxxx>
---
Documentation/driver-api/virtual_bus.rst | 112 ++++++++
MAINTAINERS | 8 +
drivers/bus/Kconfig | 14 +
drivers/bus/Makefile | 1 +
drivers/bus/virtual_bus.c | 339 +++++++++++++++++++++++
include/linux/virtual_bus.h | 64 +++++
6 files changed, 538 insertions(+)
create mode 100644 Documentation/driver-api/virtual_bus.rst
create mode 100644 drivers/bus/virtual_bus.c
create mode 100644 include/linux/virtual_bus.h
diff --git a/Documentation/driver-api/virtual_bus.rst b/Documentation/driver-api/virtual_bus.rst
new file mode 100644
index 000000000000..72e440464e95
--- /dev/null
+++ b/Documentation/driver-api/virtual_bus.rst
@@ -0,0 +1,112 @@
+===============================
+Virtual Bus Devices and Drivers
+===============================
+
+See <linux/virtual_bus.h> for the models for virtbus_device and virtbus_driver.
+This bus is meant to be a lightweight software based bus to attach generic
+devices and drivers to so that a chunk of data can be passed between them.
+
+One use case example is an rdma driver needing to connect with several
+different types of PCI LAN devices to be able to request resources from
+them (queue sets). Each LAN driver that supports rdma will register a
+virtbus_device on the virtual bus for each physical function. The rdma
+driver will register as a virtbus_driver on the virtual bus to be
+matched up with multiple virtbus_devices and receive a pointer to a
+struct containing the callbacks that the PCI LAN drivers support for
+registering with them.
+
+Sections in this document:
+ Virtbus devices
+ Virtbus drivers
+ Device Enumeration
+ Device naming and driver binding
+ Virtual Bus Structs
+ Virtual Bus API entry points
+
+Virtbus devices
+~~~~~~~~~~~~~~~
+Virtbus_devices are lightweight objects that support the minimal device
+functionality. Devices will accept a name, and then an automatically
+generated index is concatenated onto it for the virtbus_device->name.
+
+The memory backing the "void *data" element of the virtbus_device is
+expected to be allocated and freed outside the context of the bus
+operations. This memory is also expected to remain viable for the
+duration of the time that the virtbus_device is registered to the
+virtual bus. (e.g. from before the virtbus_device_add until after
+the paired virtbus_dev_del).
+
+The provided API for virtbus_dev_alloc is an efficient way of allocating
+the memory for the virtbus_device (except for the data element) and
+automatically freeing it when the device is removed from the bus.
+
+Virtbus drivers
+~~~~~~~~~~~~~~~
+Virtbus drivers register with the virtual bus to be matched with virtbus
+devices. They expect to be registered with a probe and remove callback,
+and also support shutdown, suspend, and resume callbacks. They otherwise
+follow the standard driver behavior of having discovery and enumeration
+handled in the bus infrastructure.
+
+Virtbus drivers register themselves with the API entry point virtbus_drv_reg
+and unregister with virtbus_drv_unreg.
+
+Device Enumeration
+~~~~~~~~~~~~~~~~~~
+Enumeration is handled automatically by the bus infrastructure via the
+ida_simple methods.
+
+Device naming and driver binding
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The virtbus_device.dev.name is the canonical name for the device. It is
+built from two other parts:
+
+ - virtbus_device.name (also used for matching).
+ - virtbus_device.id (generated automatically from ida_simple calls)
+
+This allows for multiple virtbus_devices with the same name, which will all
+be matched to the same virtbus_driver. Driver binding is performed by the
+driver core, invoking driver probe() after finding a match between device and driver.
+
+Virtual Bus Structs
+~~~~~~~~~~~~~~~~~~~
+struct device virtual_bus = {
+ .init_name = "virtbus",
+ .release = virtual_bus_release,
+};
+
+struct bus_type virtual_bus_type = {
+ .name = "virtbus",
+ .match = virtbus_match,
+ .probe = virtbus_probe,
+ .remove = virtbus_remove,
+ .shutdown = virtbus_shutdown,
+ .suspend = virtbus_suspend,
+ .resume = virtbus_resume,
+};
+
+struct virtbus_device {
+ const char *name;
+ int id;
+ const struct virtbus_dev_id *dev_id;
+ struct device dev;
+ void *data;
+};
+
+struct virtbus_driver {
+ int (*probe)(struct virtbus_device *);
+ int (*remove)(struct virtbus_device *);
+ void (*shutdown)(struct virtbus_device *);
+ int (*suspend)(struct virtbus_device *, pm_message_t state);
+ int (*resume)(struct virtbus_device *);
+ struct device_driver driver;
+};
+
+
+Virtual Bus API entry points
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+struct virtbus_device *virtbus_dev_alloc(const char *name, void *data)
+int virtbus_dev_add(struct virtbus_device *vdev)
+void virtbus_dev_del(struct virtbus_device *vdev)
+int virtbus_drv_register(struct virtbus_driver *vdrv, struct module *owner)
+void virtbus_drv_unregister(struct virtbus_driver *vdrv)
diff --git a/MAINTAINERS b/MAINTAINERS
index 3e57fc1d9962..0b21319dd7e8 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17353,6 +17353,14 @@ F: include/linux/vbox_utils.h
F: include/uapi/linux/vbox*.h
F: drivers/virt/vboxguest/
+VIRTUAL BUS DRIVER
+M: Jeff Kirsher <jeffrey.t.kirsher@xxxxxxxxx>
+L: intel-wired-lan@xxxxxxxxxxxxxxxx
+S: Maintained
+F: drivers/bus/virtual_bus.c
+F: include/linux/virtual_bus.h
+F: Documentation/driver-api/virtual_bus.rst
+
VIRTUAL SERIO DEVICE DRIVER
M: Stephen Chandler Paul <thatslyude@xxxxxxxxx>
S: Maintained
diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
index 6b331061d34b..30cef35b0c30 100644
--- a/drivers/bus/Kconfig
+++ b/drivers/bus/Kconfig
@@ -193,4 +193,18 @@ config DA8XX_MSTPRI
source "drivers/bus/fsl-mc/Kconfig"
+config VIRTUAL_BUS
+ tristate "lightweight Virtual Bus"
+ depends on PM
+ help
+ Provides a lightweight bus for virtbus_devices to be added to it
+ and virtbus_drivers to be registered on it. Will create a match
+ between the driver and device, then call the driver's probe with
+ the virtbus_device's struct (including a pointer for data).
+ One example is the irdma driver needing to connect with various
+ PCI LAN drivers to request resources (queues) to be able to perform
+ its function. The data in the virtbus_device created by the
+ PCI LAN driver is a set of ops (function pointers) for the irdma
+ driver to use to register and communicate with the PCI LAN driver.
+
endmenu
diff --git a/drivers/bus/Makefile b/drivers/bus/Makefile
index 16b43d3468c6..0b0ba53cbe5b 100644
--- a/drivers/bus/Makefile
+++ b/drivers/bus/Makefile
@@ -33,3 +33,4 @@ obj-$(CONFIG_UNIPHIER_SYSTEM_BUS) += uniphier-system-bus.o
obj-$(CONFIG_VEXPRESS_CONFIG) += vexpress-config.o
obj-$(CONFIG_DA8XX_MSTPRI) += da8xx-mstpri.o
+obj-$(CONFIG_VIRTUAL_BUS) += virtual_bus.o
diff --git a/drivers/bus/virtual_bus.c b/drivers/bus/virtual_bus.c
new file mode 100644
index 000000000000..af3f6d9b60f4
--- /dev/null
+++ b/drivers/bus/virtual_bus.c
@@ -0,0 +1,339 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * virtual_bus.c - lightweight software based bus for virtual devices
+ *
+ * Copyright (c) 2019-20 Intel Corporation
+ *
+ * Please see Documentation/driver-api/virtual_bus.rst for
+ * more information
+ */
+
+#include <linux/string.h>
+#include <linux/virtual_bus.h>
+#include <linux/of_irq.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/pm_runtime.h>
+#include <linux/pm_domain.h>
+#include <linux/acpi.h>
+#include <linux/device.h>
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Lightweight Virtual Bus");
+MODULE_AUTHOR("David Ertman <david.m.ertman@xxxxxxxxx>");
+MODULE_AUTHOR("Kiran Patil <kiran.patil@xxxxxxxxx>");
+
+static DEFINE_IDA(virtbus_dev_id);
+
+static void virtual_bus_release(struct device *dev)
+{
+ pr_info("Removing virtual bus device.\n");
+}
+
+struct device virtual_bus = {
+ .init_name = "virtbus",
+ .release = virtual_bus_release,
+};
+EXPORT_SYMBOL_GPL(virtual_bus);
+
+/**
+ * virtbus_add_dev - add a virtual bus device
+ * @vdev: virtual bus device to add
+ */
+int virtbus_dev_add(struct virtbus_device *vdev)
+{
+ int ret;
+
+ if (!vdev)
+ return -EINVAL;
+
+ device_initialize(&vdev->dev);
+ if (!vdev->dev.parent)
+ vdev->dev.parent = &virtual_bus;
+
+ vdev->dev.bus = &virtual_bus_type;
+ /* All device IDs are automatically allocated */
+ ret = ida_simple_get(&virtbus_dev_id, 0, 0, GFP_KERNEL);
+ if (ret < 0)
+ return ret;
+
+ vdev->id = ret;
+ dev_set_name(&vdev->dev, "%s.%d", vdev->name, vdev->id);
+
+ pr_debug("Registering VirtBus device '%s'. Parent at %s\n",
+ dev_name(&vdev->dev), dev_name(vdev->dev.parent));
+
+ ret = device_add(&vdev->dev);
+ if (!ret)
+ return ret;
+
+ /* Error adding virtual device */
+ ida_simple_remove(&virtbus_dev_id, vdev->id);
+ vdev->id = VIRTBUS_DEVID_NONE;
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(virtbus_dev_add);
+
+/**
+ * virtbus_dev_del - remove a virtual bus device
+ * vdev: virtual bus device we are removing
+ */
+void virtbus_dev_del(struct virtbus_device *vdev)
+{
+ if (!IS_ERR_OR_NULL(vdev)) {
+ device_del(&vdev->dev);
+
+ ida_simple_remove(&virtbus_dev_id, vdev->id);
+ vdev->id = VIRTBUS_DEVID_NONE;
+ }
+}
+EXPORT_SYMBOL_GPL(virtbus_dev_del);
+
+struct virtbus_object {
+ struct virtbus_device vdev;
+ char name[];
+};
+
+/**
+ * virtbus_dev_release - Destroy a virtbus device
+ * @vdev: virtual device to release
+ *
+ * Note that the vdev->data which is separately allocated needs to be
+ * separately freed on it own.
+ */
+static void virtbus_dev_release(struct device *dev)
+{
+ struct virtbus_object *vo = container_of(dev, struct virtbus_object,
+ vdev.dev);
+
+ kfree(vo);
+}
+
+/**
+ * virtbus_dev_alloc - allocate a virtbus device
+ * @name: name to associate with the vdev
+ * @data: pointer to data to be associated with this device
+ */
+struct virtbus_device *virtbus_dev_alloc(const char *name, void *data)
+{
+ struct virtbus_object *vo;
+
+ /* Create a virtbus object to contain the vdev and name. This
+ * avoids a problem with the const attribute of name in the vdev.
+ * The virtbus_object will be allocated here and freed in the
+ * release function.
+ */
+ vo = kzalloc(sizeof(*vo) + strlen(name) + 1, GFP_KERNEL);
+ if (!vo)
+ return NULL;
+
+ strcpy(vo->name, name);
+ vo->vdev.name = vo->name;
+ vo->vdev.data = data;
+ vo->vdev.dev.release = virtbus_dev_release;
+
+ return &vo->vdev;
+}
+EXPORT_SYMBOL_GPL(virtbus_dev_alloc);
+
+static int virtbus_drv_probe(struct device *_dev)
+{
+ struct virtbus_driver *vdrv = to_virtbus_drv(_dev->driver);
+ struct virtbus_device *vdev = to_virtbus_dev(_dev);
+ int ret;
+
+ ret = dev_pm_domain_attach(_dev, true);
+ if (ret) {
+ dev_warn(_dev, "Failed to attatch to PM Domain : %d\n", ret);
+ return ret;
+ }
+
+ if (vdrv->probe) {
+ ret = vdrv->probe(vdev);
+ if (ret)
+ dev_pm_domain_detach(_dev, true);
+ }
+
+ return ret;
+}
+
+static int virtbus_drv_remove(struct device *_dev)
+{
+ struct virtbus_driver *vdrv = to_virtbus_drv(_dev->driver);
+ struct virtbus_device *vdev = to_virtbus_dev(_dev);
+ int ret = 0;
+
+ if (vdrv->remove)
+ ret = vdrv->remove(vdev);
+
+ dev_pm_domain_detach(_dev, true);
+
+ return ret;
+}
+
+static void virtbus_drv_shutdown(struct device *_dev)
+{
+ struct virtbus_driver *vdrv = to_virtbus_drv(_dev->driver);
+ struct virtbus_device *vdev = to_virtbus_dev(_dev);
+
+ if (vdrv->shutdown)
+ vdrv->shutdown(vdev);
+}
+
+static int virtbus_drv_suspend(struct device *_dev, pm_message_t state)
+{
+ struct virtbus_driver *vdrv = to_virtbus_drv(_dev->driver);
+ struct virtbus_device *vdev = to_virtbus_dev(_dev);
+
+ return vdrv->suspend ? vdrv->suspend(vdev, state) : 0;
+}
+
+static int virtbus_drv_resume(struct device *_dev)
+{
+ struct virtbus_driver *vdrv = to_virtbus_drv(_dev->driver);
+ struct virtbus_device *vdev = to_virtbus_dev(_dev);
+
+ return vdrv->resume ? vdrv->resume(vdev) : 0;
+}
+
+/**
+ * virtbus_drv_register - register a driver for virtual bus devices
+ * @vdrv: virtbus_driver structure
+ * @owner: owning module/driver
+ */
+int virtbus_drv_register(struct virtbus_driver *vdrv, struct module *owner)
+{
+ vdrv->driver.owner = owner;
+ vdrv->driver.bus = &virtual_bus_type;
+ vdrv->driver.probe = virtbus_drv_probe;
+ vdrv->driver.remove = virtbus_drv_remove;
+ vdrv->driver.shutdown = virtbus_drv_shutdown;
+ vdrv->driver.suspend = virtbus_drv_suspend;
+ vdrv->driver.resume = virtbus_drv_resume;
+
+ return driver_register(&vdrv->driver);
+}
+EXPORT_SYMBOL_GPL(virtbus_drv_register);
+
+/**
+ * virtbus_drv_unregister - unregister a driver for virtual bus devices
+ * @drv: virtbus_driver structure
+ */
+void virtbus_drv_unregister(struct virtbus_driver *vdrv)
+{
+ driver_unregister(&vdrv->driver);
+}
+EXPORT_SYMBOL_GPL(virtbus_drv_unregister);
+
+static const
+struct virtbus_dev_id *virtbus_match_id(const struct virtbus_dev_id *id,
+ struct virtbus_device *vdev)
+{
+ while (id->name[0]) {
+ if (strcmp(vdev->name, id->name) == 0) {
+ vdev->dev_id = id;
+ return id;
+ }
+ id++;
+ }
+ return NULL;
+}
+
+/**
+ * virtbus_match - bind virtbus device to virtbus driver
+ * @dev: device
+ * @drv: driver
+ *
+ * Virtbus device IDs are always in "<name>.<instance>" format.
+ * Instances are automatically selected through an ida_simple_get so
+ * are positive integers. Names are taken from the device name field.
+ * Driver IDs are simple <name>. Need to extract the name from the
+ * Virtual Device compare to name of the driver.
+ */
+static int virtbus_match(struct device *dev, struct device_driver *drv)
+{
+ struct virtbus_driver *vdrv = to_virtbus_drv(drv);
+ struct virtbus_device *vdev = to_virtbus_dev(dev);
+
+ if (vdrv->id_table)
+ return virtbus_match_id(vdrv->id_table, vdev) != NULL;
+
+ return (strcmp(vdev->name, drv->name) == 0);
+}
+
+/**
+ * virtbus_probe - call probe of the virtbus_drv
+ * @dev: device struct
+ */
+static int virtbus_probe(struct device *dev)
+{
+ return dev->driver->probe ? dev->driver->probe(dev) : 0;
+}
+
+static int virtbus_remove(struct device *dev)
+{
+ return dev->driver->remove ? dev->driver->remove(dev) : 0;
+}
+
+static void virtbus_shutdown(struct device *dev)
+{
+ if (dev->driver->shutdown)
+ dev->driver->shutdown(dev);
+}
+
+static int virtbus_suspend(struct device *dev, pm_message_t state)
+{
+ if (dev->driver->suspend)
+ return dev->driver->suspend(dev, state);
+
+ return 0;
+}
+
+static int virtbus_resume(struct device *dev)
+{
+ if (dev->driver->resume)
+ return dev->driver->resume(dev);
+
+ return 0;
+}
+
+struct bus_type virtual_bus_type = {
+ .name = "virtbus",
+ .match = virtbus_match,
+ .probe = virtbus_probe,
+ .remove = virtbus_remove,
+ .shutdown = virtbus_shutdown,
+ .suspend = virtbus_suspend,
+ .resume = virtbus_resume,
+};
+EXPORT_SYMBOL_GPL(virtual_bus_type);
+
+static int __init virtual_bus_init(void)
+{
+ int err;
+
+ err = device_register(&virtual_bus);
+ if (err) {
+ put_device(&virtual_bus);
+ return err;
+ }
+
+ err = bus_register(&virtual_bus_type);
+ if (err) {
+ device_unregister(&virtual_bus);
+ return err;
+ }
+
+ pr_debug("Virtual Bus (virtbus) registered with kernel\n");
+ return err;
+}
+
+static void __exit virtual_bus_exit(void)
+{
+ bus_unregister(&virtual_bus_type);
+ device_unregister(&virtual_bus);
+}
+
+module_init(virtual_bus_init);
+module_exit(virtual_bus_exit);
diff --git a/include/linux/virtual_bus.h b/include/linux/virtual_bus.h
new file mode 100644
index 000000000000..722f020ac53b
--- /dev/null
+++ b/include/linux/virtual_bus.h
@@ -0,0 +1,64 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * virtual_bus.h - lightweight software bus
+ *
+ * Copyright (c) 2019-20 Intel Corporation
+ *
+ * Please see Documentation/driver-api/virtual_bus.rst for more information
+ */
+
+#ifndef _VIRTUAL_BUS_H_
+#define _VIRTUAL_BUS_H_
+
+#include <linux/device.h>
+
+#define VIRTBUS_DEVID_NONE (-1)
+#define VIRTBUS_NAME_SIZE 20
+
+struct virtbus_dev_id {
+ char name[VIRTBUS_NAME_SIZE];
+ u64 driver_data;
+};
+
+/* memory allocation for dev_id is expected to be done by the virtbus_driver
+ * that will match with the virtbus_device, and the matching process will
+ * copy the pointer from the matched element from the driver to the device.
+ */
+struct virtbus_device {
+ const char *name;
+ int id;
+ const struct virtbus_dev_id *dev_id;
+ struct device dev;
+ void *data;
+};
+
+struct virtbus_driver {
+ int (*probe)(struct virtbus_device *);
+ int (*remove)(struct virtbus_device *);
+ void (*shutdown)(struct virtbus_device *);
+ int (*suspend)(struct virtbus_device *, pm_message_t state);
+ int (*resume)(struct virtbus_device *);
+ struct device_driver driver;
+ const struct virtbus_dev_id *id_table;
+};
+
+#define virtbus_get_dev_id(vdev) ((vdev)->id_entry)
+#define virtbus_get_devdata(dev) ((dev)->devdata)
+#define dev_is_virtbus(dev) ((dev)->bus == &virtbus_type)
+#define to_virtbus_dev(x) container_of((x), struct virtbus_device, dev)
+#define to_virtbus_drv(drv) (container_of((drv), struct virtbus_driver, \
+ driver))
+
+extern struct bus_type virtual_bus_type;
+extern struct device virtual_bus;
+
+int virtbus_dev_add(struct virtbus_device *vdev);
+void virtbus_dev_del(struct virtbus_device *vdev);
+struct virtbus_device *virtbus_dev_alloc(const char *name, void *devdata);
+int virtbus_drv_register(struct virtbus_driver *vdrv, struct module *owner);
+void virtbus_drv_unregister(struct virtbus_driver *vdrv);
+
+int virtbus_for_each_dev(void *data, int (*fn)(struct device *, void *));
+int virtbus_for_each_drv(void *data, int(*fn)(struct device_driver *, void *));
+
+#endif /* _VIRTUAL_BUS_H_ */
--
2.21.0
