diff options
Diffstat (limited to 'drivers/base/auxiliary.c')
| -rw-r--r-- | drivers/base/auxiliary.c | 349 |
1 files changed, 295 insertions, 54 deletions
diff --git a/drivers/base/auxiliary.c b/drivers/base/auxiliary.c index adc199dfba3c..04bdbff4dbe5 100644 --- a/drivers/base/auxiliary.c +++ b/drivers/base/auxiliary.c @@ -17,34 +17,186 @@ #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-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 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, + * }; + * + * Please note that such custom ops approach is valid, but it is hard to implement + * it right without global locks per-device to protect from auxiliary_drv removal + * during call to that ops. In addition, this implementation lacks proper module + * dependency, which causes to load/unload races between auxiliary parent and devices + * modules. + * + * The most easiest way to provide these ops reliably without needing to + * have a lock is to EXPORT_SYMBOL*() them and rely on already existing + * modules infrastructure for validity and correct dependencies chains. + */ + 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; + const char *auxdev_name = dev_name(&auxdev->dev); + const char *p = strrchr(auxdev_name, '.'); + int match_size; - if (!p) - continue; - match_size = p - dev_name(&auxdev->dev); + if (!p) + return NULL; + match_size = p - auxdev_name; + for (; id->name[0]; id++) { /* 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)) + !strncmp(auxdev_name, id->name, match_size)) return id; } return NULL; } -static int auxiliary_match(struct device *dev, struct device_driver *drv) +static int auxiliary_match(struct device *dev, const struct device_driver *drv) { struct auxiliary_device *auxdev = to_auxiliary_dev(dev); - struct auxiliary_driver *auxdrv = to_auxiliary_drv(drv); + const 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) +static int auxiliary_uevent(const struct device *dev, struct kobj_uevent_env *env) { const char *name, *p; @@ -62,38 +214,32 @@ static const struct dev_pm_ops auxiliary_dev_pm_ops = { static int auxiliary_bus_probe(struct device *dev) { - struct auxiliary_driver *auxdrv = to_auxiliary_drv(dev->driver); + const 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); + ret = dev_pm_domain_attach(dev, PD_FLAG_ATTACH_POWER_ON | + PD_FLAG_DETACH_POWER_OFF); 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; + return auxdrv->probe(auxdev, auxiliary_match_id(auxdrv->id_table, auxdev)); } -static int auxiliary_bus_remove(struct device *dev) +static void auxiliary_bus_remove(struct device *dev) { - struct auxiliary_driver *auxdrv = to_auxiliary_drv(dev->driver); + const 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); - - return 0; } static void auxiliary_bus_shutdown(struct device *dev) { - struct auxiliary_driver *auxdrv = NULL; + const struct auxiliary_driver *auxdrv = NULL; struct auxiliary_device *auxdev; if (dev->driver) { @@ -105,7 +251,7 @@ static void auxiliary_bus_shutdown(struct device *dev) auxdrv->shutdown(auxdev); } -static struct bus_type auxiliary_bus_type = { +static const struct bus_type auxiliary_bus_type = { .name = "auxiliary", .probe = auxiliary_bus_probe, .remove = auxiliary_bus_remove, @@ -119,7 +265,7 @@ static struct bus_type auxiliary_bus_type = { * 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 + * 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 @@ -148,6 +294,7 @@ int auxiliary_device_init(struct auxiliary_device *auxdev) dev->bus = &auxiliary_bus_type; device_initialize(&auxdev->dev); + mutex_init(&auxdev->sysfs.lock); return 0; } EXPORT_SYMBOL_GPL(auxiliary_device_init); @@ -157,7 +304,7 @@ EXPORT_SYMBOL_GPL(auxiliary_device_init); * @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 + * 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 @@ -196,41 +343,21 @@ int __auxiliary_device_add(struct auxiliary_device *auxdev, const char *modname) 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 + * + * 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; @@ -246,7 +373,11 @@ int __auxiliary_driver_register(struct auxiliary_driver *auxdrv, auxdrv->driver.bus = &auxiliary_bus_type; auxdrv->driver.mod_name = modname; - return driver_register(&auxdrv->driver); + ret = driver_register(&auxdrv->driver); + if (ret) + kfree(auxdrv->driver.name); + + return ret; } EXPORT_SYMBOL_GPL(__auxiliary_driver_register); @@ -261,6 +392,116 @@ void auxiliary_driver_unregister(struct auxiliary_driver *auxdrv) } EXPORT_SYMBOL_GPL(auxiliary_driver_unregister); +static void auxiliary_device_release(struct device *dev) +{ + struct auxiliary_device *auxdev = to_auxiliary_dev(dev); + + of_node_put(dev->of_node); + kfree(auxdev); +} + +/** + * auxiliary_device_create - create a device on the auxiliary bus + * @dev: parent device + * @modname: module name used to create the auxiliary driver name. + * @devname: auxiliary bus device name + * @platform_data: auxiliary bus device platform data + * @id: auxiliary bus device id + * + * Helper to create an auxiliary bus device. + * The device created matches driver 'modname.devname' on the auxiliary bus. + */ +struct auxiliary_device *auxiliary_device_create(struct device *dev, + const char *modname, + const char *devname, + void *platform_data, + int id) +{ + struct auxiliary_device *auxdev; + int ret; + + auxdev = kzalloc(sizeof(*auxdev), GFP_KERNEL); + if (!auxdev) + return NULL; + + auxdev->id = id; + auxdev->name = devname; + auxdev->dev.parent = dev; + auxdev->dev.platform_data = platform_data; + auxdev->dev.release = auxiliary_device_release; + device_set_of_node_from_dev(&auxdev->dev, dev); + + ret = auxiliary_device_init(auxdev); + if (ret) { + of_node_put(auxdev->dev.of_node); + kfree(auxdev); + return NULL; + } + + ret = __auxiliary_device_add(auxdev, modname); + if (ret) { + /* + * It may look odd but auxdev should not be freed here. + * auxiliary_device_uninit() calls device_put() which call + * the device release function, freeing auxdev. + */ + auxiliary_device_uninit(auxdev); + return NULL; + } + + return auxdev; +} +EXPORT_SYMBOL_GPL(auxiliary_device_create); + +/** + * auxiliary_device_destroy - remove an auxiliary device + * @auxdev: pointer to the auxdev to be removed + * + * Helper to remove an auxiliary device created with + * auxiliary_device_create() + */ +void auxiliary_device_destroy(void *auxdev) +{ + struct auxiliary_device *_auxdev = auxdev; + + auxiliary_device_delete(_auxdev); + auxiliary_device_uninit(_auxdev); +} +EXPORT_SYMBOL_GPL(auxiliary_device_destroy); + +/** + * __devm_auxiliary_device_create - create a managed device on the auxiliary bus + * @dev: parent device + * @modname: module name used to create the auxiliary driver name. + * @devname: auxiliary bus device name + * @platform_data: auxiliary bus device platform data + * @id: auxiliary bus device id + * + * Device managed helper to create an auxiliary bus device. + * The device created matches driver 'modname.devname' on the auxiliary bus. + */ +struct auxiliary_device *__devm_auxiliary_device_create(struct device *dev, + const char *modname, + const char *devname, + void *platform_data, + int id) +{ + struct auxiliary_device *auxdev; + int ret; + + auxdev = auxiliary_device_create(dev, modname, devname, platform_data, id); + if (!auxdev) + return NULL; + + ret = devm_add_action_or_reset(dev, auxiliary_device_destroy, + auxdev); + if (ret) + return NULL; + + return auxdev; +} +EXPORT_SYMBOL_GPL(__devm_auxiliary_device_create); + void __init auxiliary_bus_init(void) { WARN_ON(bus_register(&auxiliary_bus_type)); |