auxiliary.c
// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (c) 2019-2020 Intel Corporation
*
* Please see Documentation/driver-api/auxiliary_bus.rst for more information.
*/
#define pr_fmt(fmt) "%s:%s: " fmt, KBUILD_MODNAME, __func__
#include <linux/device.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/pm_domain.h>
#include <linux/pm_runtime.h>
#include <linux/string.h>
#include <linux/auxiliary_bus.h>
#include "base.h"
/**
* DOC: PURPOSE
*
* In some subsystems, the functionality of the core device (PCI/ACPI/other) is
* too complex for a single device to be managed by a monolithic driver (e.g.
* Sound Open Firmware), multiple devices might implement a common intersection
* of functionality (e.g. NICs + RDMA), or a driver may want to export an
* interface for another subsystem to drive (e.g. SIOV Physical Function export
* Virtual Function management). A split of the functionality into child-
* devices representing sub-domains of functionality makes it possible to
* compartmentalize, layer, and distribute domain-specific concerns via a Linux
* device-driver model.
*
* An example for this kind of requirement is the audio subsystem where a
* single IP is handling multiple entities such as HDMI, Soundwire, local
* devices such as mics/speakers etc. The split for the core's functionality
* can be arbitrary or be defined by the DSP firmware topology and include
* hooks for test/debug. This allows for the audio core device to be minimal
* and focused on hardware-specific control and communication.
*
* Each auxiliary_device represents a part of its parent functionality. The
* generic behavior can be extended and specialized as needed by encapsulating
* an auxiliary_device within other domain-specific structures and the use of
* .ops callbacks. Devices on the auxiliary bus do not share any structures and
* the use of a communication channel with the parent is domain-specific.
*
* Note that ops are intended as a way to augment instance behavior within a
* class of auxiliary devices, it is not the mechanism for exporting common
* infrastructure from the parent. Consider EXPORT_SYMBOL_NS() to convey
* infrastructure from the parent module to the auxiliary module(s).
*/
/**
* DOC: USAGE
*
* The auxiliary bus is to be used when a driver and one or more kernel
* modules, who share a common header file with the driver, need a mechanism to
* connect and provide access to a shared object allocated by the
* auxiliary_device's registering driver. The registering driver for the
* auxiliary_device(s) and the kernel module(s) registering auxiliary_drivers
* can be from the same subsystem, or from multiple subsystems.
*
* The emphasis here is on a common generic interface that keeps subsystem
* customization out of the bus infrastructure.
*
* One example is a PCI network device that is RDMA-capable and exports a child
* device to be driven by an auxiliary_driver in the RDMA subsystem. The PCI
* driver allocates and registers an auxiliary_device for each physical
* function on the NIC. The RDMA driver registers an auxiliary_driver that
* claims each of these auxiliary_devices. This conveys data/ops published by
* the parent PCI device/driver to the RDMA auxiliary_driver.
*
* Another use case is for the PCI device to be split out into multiple sub
* functions. For each sub function an auxiliary_device is created. A PCI sub
* function driver binds to such devices that creates its own one or more class
* devices. A PCI sub function auxiliary device is likely to be contained in a
* struct with additional attributes such as user defined sub function number
* and optional attributes such as resources and a link to the parent device.
* These attributes could be used by systemd/udev; and hence should be
* initialized before a driver binds to an auxiliary_device.
*
* A key requirement for utilizing the auxiliary bus is that there is no
* dependency on a physical bus, device, register accesses or regmap support.
* These individual devices split from the core cannot live on the platform bus
* as they are not physical devices that are controlled by DT/ACPI. The same
* argument applies for not using MFD in this scenario as MFD relies on
* individual function devices being physical devices.
*/
/**
* DOC: EXAMPLE
*
* Auxiliary devices are created and registered by a subsystem-level core
* device that needs to break up its functionality into smaller fragments. One
* way to extend the scope of an auxiliary_device is to encapsulate it within a
* domain- pecific structure defined by the parent device. This structure
* contains the auxiliary_device and any associated shared data/callbacks
* needed to establish the connection with the parent.
*
* An example is:
*
* .. code-block:: c
*
* struct foo {
* struct auxiliary_device auxdev;
* void (*connect)(struct auxiliary_device *auxdev);
* void (*disconnect)(struct auxiliary_device *auxdev);
* void *data;
* };
*
* The parent device then registers the auxiliary_device by calling
* auxiliary_device_init(), and then auxiliary_device_add(), with the pointer
* to the auxdev member of the above structure. The parent provides a name for
* the auxiliary_device that, combined with the parent's KBUILD_MODNAME,
* creates a match_name that is be used for matching and binding with a driver.
*
* Whenever an auxiliary_driver is registered, based on the match_name, the
* auxiliary_driver's probe() is invoked for the matching devices. The
* auxiliary_driver can also be encapsulated inside custom drivers that make
* the core device's functionality extensible by adding additional
* domain-specific ops as follows:
*
* .. code-block:: c
*
* struct my_ops {
* void (*send)(struct auxiliary_device *auxdev);
* void (*receive)(struct auxiliary_device *auxdev);
* };
*
*
* struct my_driver {
* struct auxiliary_driver auxiliary_drv;
* const struct my_ops ops;
* };
*
* An example of this type of usage is:
*
* .. code-block:: c
*
* const struct auxiliary_device_id my_auxiliary_id_table[] = {
* { .name = "foo_mod.foo_dev" },
* { },
* };
*
* const struct my_ops my_custom_ops = {
* .send = my_tx,
* .receive = my_rx,
* };
*
* const struct my_driver my_drv = {
* .auxiliary_drv = {
* .name = "myauxiliarydrv",
* .id_table = my_auxiliary_id_table,
* .probe = my_probe,
* .remove = my_remove,
* .shutdown = my_shutdown,
* },
* .ops = my_custom_ops,
* };
*/
static const struct auxiliary_device_id *auxiliary_match_id(const struct auxiliary_device_id *id,
const struct auxiliary_device *auxdev)
{
for (; id->name[0]; id++) {
const char *p = strrchr(dev_name(&auxdev->dev), '.');
int match_size;
if (!p)
continue;
match_size = p - dev_name(&auxdev->dev);
/* use dev_name(&auxdev->dev) prefix before last '.' char to match to */
if (strlen(id->name) == match_size &&
!strncmp(dev_name(&auxdev->dev), id->name, match_size))
return id;
}
return NULL;
}
static int auxiliary_match(struct device *dev, struct device_driver *drv)
{
struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
struct auxiliary_driver *auxdrv = to_auxiliary_drv(drv);
return !!auxiliary_match_id(auxdrv->id_table, auxdev);
}
static int auxiliary_uevent(struct device *dev, struct kobj_uevent_env *env)
{
const char *name, *p;
name = dev_name(dev);
p = strrchr(name, '.');
return add_uevent_var(env, "MODALIAS=%s%.*s", AUXILIARY_MODULE_PREFIX,
(int)(p - name), name);
}
static const struct dev_pm_ops auxiliary_dev_pm_ops = {
SET_RUNTIME_PM_OPS(pm_generic_runtime_suspend, pm_generic_runtime_resume, NULL)
SET_SYSTEM_SLEEP_PM_OPS(pm_generic_suspend, pm_generic_resume)
};
static int auxiliary_bus_probe(struct device *dev)
{
struct auxiliary_driver *auxdrv = to_auxiliary_drv(dev->driver);
struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
int ret;
ret = dev_pm_domain_attach(dev, true);
if (ret) {
dev_warn(dev, "Failed to attach to PM Domain : %d\n", ret);
return ret;
}
ret = auxdrv->probe(auxdev, auxiliary_match_id(auxdrv->id_table, auxdev));
if (ret)
dev_pm_domain_detach(dev, true);
return ret;
}
static void auxiliary_bus_remove(struct device *dev)
{
struct auxiliary_driver *auxdrv = to_auxiliary_drv(dev->driver);
struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
if (auxdrv->remove)
auxdrv->remove(auxdev);
dev_pm_domain_detach(dev, true);
}
static void auxiliary_bus_shutdown(struct device *dev)
{
struct auxiliary_driver *auxdrv = NULL;
struct auxiliary_device *auxdev;
if (dev->driver) {
auxdrv = to_auxiliary_drv(dev->driver);
auxdev = to_auxiliary_dev(dev);
}
if (auxdrv && auxdrv->shutdown)
auxdrv->shutdown(auxdev);
}
static struct bus_type auxiliary_bus_type = {
.name = "auxiliary",
.probe = auxiliary_bus_probe,
.remove = auxiliary_bus_remove,
.shutdown = auxiliary_bus_shutdown,
.match = auxiliary_match,
.uevent = auxiliary_uevent,
.pm = &auxiliary_dev_pm_ops,
};
/**
* auxiliary_device_init - check auxiliary_device and initialize
* @auxdev: auxiliary device struct
*
* This is the second step in the three-step process to register an
* auxiliary_device.
*
* When this function returns an error code, then the device_initialize will
* *not* have been performed, and the caller will be responsible to free any
* memory allocated for the auxiliary_device in the error path directly.
*
* It returns 0 on success. On success, the device_initialize has been
* performed. After this point any error unwinding will need to include a call
* to auxiliary_device_uninit(). In this post-initialize error scenario, a call
* to the device's .release callback will be triggered, and all memory clean-up
* is expected to be handled there.
*/
int auxiliary_device_init(struct auxiliary_device *auxdev)
{
struct device *dev = &auxdev->dev;
if (!dev->parent) {
pr_err("auxiliary_device has a NULL dev->parent\n");
return -EINVAL;
}
if (!auxdev->name) {
pr_err("auxiliary_device has a NULL name\n");
return -EINVAL;
}
dev->bus = &auxiliary_bus_type;
device_initialize(&auxdev->dev);
return 0;
}
EXPORT_SYMBOL_GPL(auxiliary_device_init);
/**
* __auxiliary_device_add - add an auxiliary bus device
* @auxdev: auxiliary bus device to add to the bus
* @modname: name of the parent device's driver module
*
* This is the third step in the three-step process to register an
* auxiliary_device.
*
* This function must be called after a successful call to
* auxiliary_device_init(), which will perform the device_initialize. This
* means that if this returns an error code, then a call to
* auxiliary_device_uninit() must be performed so that the .release callback
* will be triggered to free the memory associated with the auxiliary_device.
*
* The expectation is that users will call the "auxiliary_device_add" macro so
* that the caller's KBUILD_MODNAME is automatically inserted for the modname
* parameter. Only if a user requires a custom name would this version be
* called directly.
*/
int __auxiliary_device_add(struct auxiliary_device *auxdev, const char *modname)
{
struct device *dev = &auxdev->dev;
int ret;
if (!modname) {
dev_err(dev, "auxiliary device modname is NULL\n");
return -EINVAL;
}
ret = dev_set_name(dev, "%s.%s.%d", modname, auxdev->name, auxdev->id);
if (ret) {
dev_err(dev, "auxiliary device dev_set_name failed: %d\n", ret);
return ret;
}
ret = device_add(dev);
if (ret)
dev_err(dev, "adding auxiliary device failed!: %d\n", ret);
return ret;
}
EXPORT_SYMBOL_GPL(__auxiliary_device_add);
/**
* auxiliary_find_device - auxiliary device iterator for locating a particular device.
* @start: Device to begin with
* @data: Data to pass to match function
* @match: Callback function to check device
*
* This function returns a reference to a device that is 'found'
* for later use, as determined by the @match callback.
*
* The reference returned should be released with put_device().
*
* The callback should return 0 if the device doesn't match and non-zero
* if it does. If the callback returns non-zero, this function will
* return to the caller and not iterate over any more devices.
*/
struct auxiliary_device *auxiliary_find_device(struct device *start,
const void *data,
int (*match)(struct device *dev, const void *data))
{
struct device *dev;
dev = bus_find_device(&auxiliary_bus_type, start, data, match);
if (!dev)
return NULL;
return to_auxiliary_dev(dev);
}
EXPORT_SYMBOL_GPL(auxiliary_find_device);
/**
* __auxiliary_driver_register - register a driver for auxiliary bus devices
* @auxdrv: auxiliary_driver structure
* @owner: owning module/driver
* @modname: KBUILD_MODNAME for parent driver
*
* The expectation is that users will call the "auxiliary_driver_register"
* macro so that the caller's KBUILD_MODNAME is automatically inserted for the
* modname parameter. Only if a user requires a custom name would this version
* be called directly.
*/
int __auxiliary_driver_register(struct auxiliary_driver *auxdrv,
struct module *owner, const char *modname)
{
int ret;
if (WARN_ON(!auxdrv->probe) || WARN_ON(!auxdrv->id_table))
return -EINVAL;
if (auxdrv->name)
auxdrv->driver.name = kasprintf(GFP_KERNEL, "%s.%s", modname,
auxdrv->name);
else
auxdrv->driver.name = kasprintf(GFP_KERNEL, "%s", modname);
if (!auxdrv->driver.name)
return -ENOMEM;
auxdrv->driver.owner = owner;
auxdrv->driver.bus = &auxiliary_bus_type;
auxdrv->driver.mod_name = modname;
ret = driver_register(&auxdrv->driver);
if (ret)
kfree(auxdrv->driver.name);
return ret;
}
EXPORT_SYMBOL_GPL(__auxiliary_driver_register);
/**
* auxiliary_driver_unregister - unregister a driver
* @auxdrv: auxiliary_driver structure
*/
void auxiliary_driver_unregister(struct auxiliary_driver *auxdrv)
{
driver_unregister(&auxdrv->driver);
kfree(auxdrv->driver.name);
}
EXPORT_SYMBOL_GPL(auxiliary_driver_unregister);
void __init auxiliary_bus_init(void)
{
WARN_ON(bus_register(&auxiliary_bus_type));
}