Add auxiliary bus support

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>
Co-developed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Co-developed-by: Fred Oh <fred.oh@linux.intel.com>
Co-developed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Kiran Patil <kiran.patil@intel.com>
Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Signed-off-by: Fred Oh <fred.oh@linux.intel.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Dave Ertman <david.m.ertman@intel.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>
Reviewed-by: Martin Habets <mhabets@solarflare.com>
Link: https://lore.kernel.org/r/20201113161859.1775473-2-david.m.ertman@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/160695681289.505290.8978295443574440604.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 272 insertions, 0 deletions

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..ef2af417438b
--- /dev/null
+++ b/drivers/base/auxiliary.c
@@ -0,0 +1,268 @@
+// 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/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_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 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.
+ *
+ * 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) {
+		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 v2");
+MODULE_DESCRIPTION("Auxiliary Bus");
+MODULE_AUTHOR("David Ertman <david.m.ertman@intel.com>");
+MODULE_AUTHOR("Kiran Patil <kiran.patil@intel.com>");