[PATCH v3 01/10] Add auxiliary bus support

Dave Ertman
2020-10-23T00:35:26Z

Add support for the Auxiliary Bus, auxiliary_device and auxiliary_driver.
It enables drivers to create an auxiliary_device and bind an
auxiliary_driver to it.

The bus supports probe/remove shutdown and suspend/resume callbacks.
Each auxiliary_device has a unique string based id; driver binds to
an auxiliary_device based on this id through the bus.

Co-developed-by: Kiran Patil <kiran.patil@intel.com>
Signed-off-by: Kiran Patil <kiran.patil@intel.com>
Co-developed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Co-developed-by: Fred Oh <fred.oh@linux.intel.com>
Signed-off-by: Fred Oh <fred.oh@linux.intel.com>
Co-developed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Shiraz Saleem <shiraz.saleem@intel.com>
Reviewed-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Ertman <david.m.ertman@intel.com>
---
Documentation/driver-api/auxiliary_bus.rst | 228 ++++++++++++++++++
Documentation/driver-api/index.rst | 1 +
drivers/base/Kconfig | 3 +
drivers/base/Makefile | 1 +
drivers/base/auxiliary.c | 267 +++++++++++++++++++++
include/linux/auxiliary_bus.h | 78 ++++++
include/linux/mod_devicetable.h | 8 +
scripts/mod/devicetable-offsets.c | 3 +
scripts/mod/file2alias.c | 8 +
9 files changed, 597 insertions(+)
create mode 100644 Documentation/driver-api/auxiliary_bus.rst
create mode 100644 drivers/base/auxiliary.c
create mode 100644 include/linux/auxiliary_bus.h

diff --git a/Documentation/driver-api/auxiliary_bus.rst b/Documentation/driver-api/auxiliary_bus.rst
new file mode 100644
index 000000000000..500f29692c81
--- /dev/null
+++ b/Documentation/driver-api/auxiliary_bus.rst
@@ -0,0 +1,228 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+=============
+Auxiliary Bus
+=============
+
+In some subsystems, the functionality of the core device (PCI/ACPI/other) is
+too complex for a single device to be managed as a monolithic block or a part of
+the functionality needs to be exposed to a different subsystem. Splitting the
+functionality into smaller orthogonal devices would make it easier to manage
+data, power management and domain-specific interaction with the hardware. A key
+requirement for such a split 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.
+
+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.
+
+The auxiliary bus is intended to be minimal, generic and avoid domain-specific
+assumptions. 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.
+
+When Should the Auxiliary Bus Be Used
+=====================================
+
+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 could be a multi-port PCI network device that is rdma-capable and
+needs to export this functionality and attach to an rdma driver in another
+subsystem. The PCI driver will allocate and register an auxiliary_device for
+each physical function on the NIC. The rdma driver will register an
+auxiliary_driver that will be matched with and probed for each of these
+auxiliary_devices. This will give the rdma driver access to the shared data/ops
+in the PCI drivers shared object to establish a connection with the PCI driver.
+
+Another use case is for the PCI device to be split out into multiple sub
+functions. For each sub function an auxiliary_device will be created. A PCI
+sub function driver will bind to such devices that will create its own one or
+more class devices. A PCI sub function auxiliary device will likely 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.
+
+Auxiliary Device
+================
+
+An auxiliary_device is created and registered to represent a part of its parent
+device's functionality. It is given a name that, combined with the registering
+drivers KBUILD_MODNAME, creates a match_name that is used for driver binding,
+and an id that combined with the match_name provide a unique name to register
+with the bus subsystem.
+
+Registering an auxiliary_device is a two-step process. First you must call
+auxiliary_device_init(), which will check several aspects of the
+auxiliary_device struct and perform a device_initialize(). After this step
+completes, any error state must have a call to auxiliary_device_unin() in its
+resolution path. The second step in registering an auxiliary_device is to
+perform a call to auxiliary_device_add(), which will set the name of the device
+and add the device to the bus.
+
+Unregistering an auxiliary_device is also a two-step process to mirror the
+register process. First will be a call to auxiliary_device_delete(), then
+followed by a call to auxiliary_device_unin().
+
+.. code-block:: c
+
+ struct auxiliary_device {
+ struct device dev;
+ const char *name;
+ u32 id;
+ };
+
+If two auxiliary_devices both with a match_name "mod.foo" are registered onto
+the bus, they must have unique id values (e.g. "x" and "y") so that the
+registered devices names will be "mod.foo.x" and "mod.foo.y". If match_name +
+id are not unique, then the device_add will fail and generate an error message.
+
+The auxiliary_device.dev.type.release or auxiliary_device.dev.release must be
+populated with a non-NULL pointer to successfully register the auxiliary_device.
+
+The auxiliary_device.dev.parent must also be populated.
+
+Auxiliary Device Memory Model and Lifespan
+------------------------------------------
+
+When a kernel driver registers an auxiliary_device on the auxiliary bus, we will
+use the nomenclature to refer to this kernel driver as a registering driver. It
+is the entity that will allocate memory for the auxiliary_device and register it
+on the auxiliary bus. It is important to note that, as opposed to the platform
+bus, the registering driver is wholly responsible for the management for the
+memory used for the driver object.
+
+A parent object, defined in the shared header file, will contain the
+auxiliary_device. It will also contain a pointer to the shared object(s), which
+will also be defined in the shared header. Both the parent object and the
+shared object(s) will be allocated by the registering driver. This layout
+allows the auxiliary_driver's registering module to perform a container_of()
+call to go from the pointer to the auxiliary_device, that is passed during the
+call to the auxiliary_driver's probe function, up to the parent object, and then
+have access to the shared object(s).
+
+The memory for the auxiliary_device will be freed only in its release()
+callback flow as defined by its registering driver.
+
+The memory for the shared object(s) must have a lifespan equal to, or greater
+than, the lifespan of the memory for the auxiliary_device. The auxiliary_driver
+should only consider that this shared object is valid as long as the
+auxiliary_device is still registered on the auxiliary bus. It is up to the
+registering driver to manage (e.g. free or keep available) the memory for the
+shared object beyond the life of the auxiliary_device.
+
+Registering driver must unregister all auxiliary devices before its registering
+parent device's remove() is completed.
+
+Auxiliary Drivers
+=================
+
+Auxiliary drivers follow the standard driver model convention, where
+discovery/enumeration is handled by the core, and drivers
+provide probe() and remove() methods. They support power management
+and shutdown notifications using the standard conventions.
+
+.. code-block:: c
+
+ struct auxiliary_driver {
+ int (*probe)(struct auxiliary_device *,
+ const struct auxiliary_device_id *id);
+ int (*remove)(struct auxiliary_device *);
+ void (*shutdown)(struct auxiliary_device *);
+ int (*suspend)(struct auxiliary_device *, pm_message_t);
+ int (*resume)(struct auxiliary_device *);
+ struct device_driver driver;
+ const struct auxiliary_device_id *id_table;
+ };
+
+Auxiliary drivers register themselves with the bus by calling
+auxiliary_driver_register(). The id_table contains the match_names of auxiliary
+devices that a driver can bind with.
+
+Example Usage
+=============
+
+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 would be to encapsulate it within a
+domain-specific 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 would be:
+
+.. 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 would then register 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 would provide a name for
+the auxiliary_device that, combined with the parent's KBUILD_MODNAME, will
+create a match_name that will 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 would be:
+
+.. 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,
+ };
diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst
index 987d6e74ea6a..af206dc816ca 100644
--- a/Documentation/driver-api/index.rst
+++ b/Documentation/driver-api/index.rst
@@ -72,6 +72,7 @@ available subsections can be seen below.
thermal/index
fpga/index
acpi/index
+ auxiliary_bus
backlight/lp855x-driver.rst
connector
console
diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
index 8d7001712062..040be48ce046 100644
--- a/drivers/base/Kconfig
+++ b/drivers/base/Kconfig
@@ -1,6 +1,9 @@
# SPDX-License-Identifier: GPL-2.0
menu "Generic Driver Options"

+config AUXILIARY_BUS
+ bool
+
config UEVENT_HELPER
bool "Support for uevent helper"
help
diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 41369fc7004f..5e7bf9669a81 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile
@@ -7,6 +7,7 @@ obj-y := component.o core.o bus.o dd.o syscore.o \
attribute_container.o transport_class.o \
topology.o container.o property.o cacheinfo.o \
swnode.o
+obj-$(CONFIG_AUXILIARY_BUS) += auxiliary.o
obj-$(CONFIG_DEVTMPFS) += devtmpfs.o
obj-y += power/
obj-$(CONFIG_ISA_BUS_API) += isa.o
diff --git a/drivers/base/auxiliary.c b/drivers/base/auxiliary.c
new file mode 100644
index 000000000000..b7c66785352e
--- /dev/null
+++ b/drivers/base/auxiliary.c
@@ -0,0 +1,267 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Software based bus for Auxiliary devices
+ *
+ * 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/module.h>
+#include <linux/pm_domain.h>
+#include <linux/pm_runtime.h>
+#include <linux/string.h>
+#include <linux/auxiliary_bus.h>
+
+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 int auxiliary_bus_remove(struct device *dev)
+{
+ struct auxiliary_driver *auxdrv = to_auxiliary_drv(dev->driver);
+ struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
+ int ret = 0;
+
+ if (auxdrv->remove)
+ ret = auxdrv->remove(auxdev);
+ dev_pm_domain_detach(dev, true);
+
+ return ret;
+}
+
+static void auxiliary_bus_shutdown(struct device *dev)
+{
+ struct auxiliary_driver *auxdrv = to_auxiliary_drv(dev->driver);
+ struct auxiliary_device *auxdev = to_auxiliary_dev(dev);
+
+ if (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 first step in the two-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_init().
+ * In this post-initialize error scenario, a call to the device's .release callback will be
+ * triggered by auxiliary_device_uninit(), 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 second step in the two-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.
+ */
+int __auxiliary_device_add(struct auxiliary_device *auxdev, const char *modname)
+{
+ struct device *dev = &auxdev->dev;
+ int ret;
+
+ if (!modname) {
+ pr_err("auxiliary device modname is NULL\n");
+ return -EINVAL;
+ }
+
+ ret = dev_set_name(dev, "%s.%s.%d", modname, auxdev->name, auxdev->id);
+ if (ret) {
+ pr_err("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 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
+ */
+int __auxiliary_driver_register(struct auxiliary_driver *auxdrv, struct module *owner,
+ const char *modname)
+{
+ 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;
+
+ return driver_register(&auxdrv->driver);
+}
+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);
+
+static int __init auxiliary_bus_init(void)
+{
+ return bus_register(&auxiliary_bus_type);
+}
+
+static void __exit auxiliary_bus_exit(void)
+{
+ bus_unregister(&auxiliary_bus_type);
+}
+
+module_init(auxiliary_bus_init);
+module_exit(auxiliary_bus_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Auxiliary Bus");
+MODULE_AUTHOR("David Ertman <david.m.ertman@intel.com>");
+MODULE_AUTHOR("Kiran Patil <kiran.patil@intel.com>");
diff --git a/include/linux/auxiliary_bus.h b/include/linux/auxiliary_bus.h
new file mode 100644
index 000000000000..282fbf7bf9af
--- /dev/null
+++ b/include/linux/auxiliary_bus.h
@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2019-2020 Intel Corporation
+ *
+ * Please see Documentation/driver-api/auxiliary_bus.rst for more information.
+ */
+
+#ifndef _AUXILIARY_BUS_H_
+#define _AUXILIARY_BUS_H_
+
+#include <linux/device.h>
+#include <linux/mod_devicetable.h>
+#include <linux/slab.h>
+
+struct auxiliary_device {
+ struct device dev;
+ const char *name;
+ u32 id;
+};
+
+struct auxiliary_driver {
+ int (*probe)(struct auxiliary_device *auxdev, const struct auxiliary_device_id *id);
+ int (*remove)(struct auxiliary_device *auxdev);
+ void (*shutdown)(struct auxiliary_device *auxdev);
+ int (*suspend)(struct auxiliary_device *auxdev, pm_message_t state);
+ int (*resume)(struct auxiliary_device *auxdev);
+ const char *name;
+ struct device_driver driver;
+ const struct auxiliary_device_id *id_table;
+};
+
+static inline struct auxiliary_device *to_auxiliary_dev(struct device *dev)
+{
+ return container_of(dev, struct auxiliary_device, dev);
+}
+
+static inline struct auxiliary_driver *to_auxiliary_drv(struct device_driver *drv)
+{
+ return container_of(drv, struct auxiliary_driver, driver);
+}
+
+int auxiliary_device_init(struct auxiliary_device *auxdev);
+int __auxiliary_device_add(struct auxiliary_device *auxdev, const char *modname);
+#define auxiliary_device_add(auxdev) __auxiliary_device_add(auxdev, KBUILD_MODNAME)
+
+static inline void auxiliary_device_uninit(struct auxiliary_device *auxdev)
+{
+ put_device(&auxdev->dev);
+}
+
+static inline void auxiliary_device_delete(struct auxiliary_device *auxdev)
+{
+ device_del(&auxdev->dev);
+}
+
+int __auxiliary_driver_register(struct auxiliary_driver *auxdrv, struct module *owner,
+ const char *modname);
+#define auxiliary_driver_register(auxdrv) \
+ __auxiliary_driver_register(auxdrv, THIS_MODULE, KBUILD_MODNAME)
+
+void auxiliary_driver_unregister(struct auxiliary_driver *auxdrv);
+
+/**
+ * module_auxiliary_driver() - Helper macro for registering an auxiliary driver
+ * @__auxiliary_driver: auxiliary driver struct
+ *
+ * Helper macro for auxiliary drivers which do not do anything special in
+ * module init/exit. This eliminates a lot of boilerplate. Each module may only
+ * use this macro once, and calling it replaces module_init() and module_exit()
+ */
+#define module_auxiliary_driver(__auxiliary_driver) \
+ module_driver(__auxiliary_driver, auxiliary_driver_register, auxiliary_driver_unregister)
+
+struct auxiliary_device *
+auxiliary_find_device(struct device *start, const void *data,
+ int (*match)(struct device *dev, const void *data));
+
+#endif /* _AUXILIARY_BUS_H_ */
diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
index 5b08a473cdba..c425290b21e2 100644
--- a/include/linux/mod_devicetable.h
+++ b/include/linux/mod_devicetable.h
@@ -838,4 +838,12 @@ struct mhi_device_id {
kernel_ulong_t driver_data;
};

+#define AUXILIARY_NAME_SIZE 32
+#define AUXILIARY_MODULE_PREFIX "auxiliary:"
+
+struct auxiliary_device_id {
+ char name[AUXILIARY_NAME_SIZE];
+ kernel_ulong_t driver_data;
+};
+
#endif /* LINUX_MOD_DEVICETABLE_H */
diff --git a/scripts/mod/devicetable-offsets.c b/scripts/mod/devicetable-offsets.c
index 27007c18e754..e377f52dbfa3 100644
--- a/scripts/mod/devicetable-offsets.c
+++ b/scripts/mod/devicetable-offsets.c
@@ -243,5 +243,8 @@ int main(void)
DEVID(mhi_device_id);
DEVID_FIELD(mhi_device_id, chan);

+ DEVID(auxiliary_device_id);
+ DEVID_FIELD(auxiliary_device_id, name);
+
return 0;
}
diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
index 2417dd1dee33..fb4827027536 100644
--- a/scripts/mod/file2alias.c
+++ b/scripts/mod/file2alias.c
@@ -1364,6 +1364,13 @@ static int do_mhi_entry(const char *filename, void *symval, char *alias)
{
DEF_FIELD_ADDR(symval, mhi_device_id, chan);
sprintf(alias, MHI_DEVICE_MODALIAS_FMT, *chan);
+ return 1;
+}
+
+static int do_auxiliary_entry(const char *filename, void *symval, char *alias)
+{
+ DEF_FIELD_ADDR(symval, auxiliary_device_id, name);
+ sprintf(alias, AUXILIARY_MODULE_PREFIX "%s", *name);

return 1;
}
@@ -1442,6 +1449,7 @@ static const struct devtable devtable[] = {
{"tee", SIZE_tee_client_device_id, do_tee_entry},
{"wmi", SIZE_wmi_device_id, do_wmi_entry},
{"mhi", SIZE_mhi_device_id, do_mhi_entry},
+ {"auxiliary", SIZE_auxiliary_device_id, do_auxiliary_entry},
};

/* Create MODULE_ALIAS() statements.
--
2.26.2