diff options
| -rw-r--r-- | Documentation/driver-api/device_connection.rst | 43 | ||||
| -rw-r--r-- | drivers/base/Makefile | 3 | ||||
| -rw-r--r-- | drivers/base/devcon.c | 136 | ||||
| -rw-r--r-- | include/linux/device.h | 22 |
4 files changed, 203 insertions, 1 deletions
diff --git a/Documentation/driver-api/device_connection.rst b/Documentation/driver-api/device_connection.rst new file mode 100644 index 000000000000..affbc5566ab0 --- /dev/null +++ b/Documentation/driver-api/device_connection.rst @@ -0,0 +1,43 @@ +================== +Device connections +================== + +Introduction +------------ + +Devices often have connections to other devices that are outside of the direct +child/parent relationship. A serial or network communication controller, which +could be a PCI device, may need to be able to get a reference to its PHY +component, which could be attached for example to the I2C bus. Some device +drivers need to be able to control the clocks or the GPIOs for their devices, +and so on. + +Device connections are generic descriptions of any type of connection between +two separate devices. + +Device connections alone do not create a dependency between the two devices. +They are only descriptions which are not tied to either of the devices directly. +A dependency between the two devices exists only if one of the two endpoint +devices requests a reference to the other. The descriptions themselves can be +defined in firmware (not yet supported) or they can be built-in. + +Usage +----- + +Device connections should exist before device ``->probe`` callback is called for +either endpoint device in the description. If the connections are defined in +firmware, this is not a problem. It should be considered if the connection +descriptions are "built-in", and need to be added separately. + +The connection description consists of the names of the two devices with the +connection, i.e. the endpoints, and unique identifier for the connection which +is needed if there are multiple connections between the two devices. + +After a description exists, the devices in it can request reference to the other +endpoint device, or they can request the description itself. + +API +--- + +.. kernel-doc:: drivers/base/devcon.c + : functions: device_connection_find_match device_connection_find device_connection_add device_connection_remove diff --git a/drivers/base/Makefile b/drivers/base/Makefile index e32a52490051..12a7f64d35a9 100644 --- a/drivers/base/Makefile +++ b/drivers/base/Makefile @@ -5,7 +5,8 @@ obj-y := component.o core.o bus.o dd.o syscore.o \ driver.o class.o platform.o \ cpu.o firmware.o init.o map.o devres.o \ attribute_container.o transport_class.o \ - topology.o container.o property.o cacheinfo.o + topology.o container.o property.o cacheinfo.o \ + devcon.o obj-$(CONFIG_DEVTMPFS) += devtmpfs.o obj-$(CONFIG_DMA_CMA) += dma-contiguous.o obj-y += power/ diff --git a/drivers/base/devcon.c b/drivers/base/devcon.c new file mode 100644 index 000000000000..d427e806cd73 --- /dev/null +++ b/drivers/base/devcon.c @@ -0,0 +1,136 @@ +// SPDX-License-Identifier: GPL-2.0 +/** + * Device connections + * + * Copyright (C) 2018 Intel Corporation + * Author: Heikki Krogerus <heikki.krogerus@linux.intel.com> + */ + +#include <linux/device.h> + +static DEFINE_MUTEX(devcon_lock); +static LIST_HEAD(devcon_list); + +/** + * device_connection_find_match - Find physical connection to a device + * @dev: Device with the connection + * @con_id: Identifier for the connection + * @data: Data for the match function + * @match: Function to check and convert the connection description + * + * Find a connection with unique identifier @con_id between @dev and another + * device. @match will be used to convert the connection description to data the + * caller is expecting to be returned. + */ +void *device_connection_find_match(struct device *dev, const char *con_id, + void *data, + void *(*match)(struct device_connection *con, + int ep, void *data)) +{ + const char *devname = dev_name(dev); + struct device_connection *con; + void *ret = NULL; + int ep; + + if (!match) + return NULL; + + mutex_lock(&devcon_lock); + + list_for_each_entry(con, &devcon_list, list) { + ep = match_string(con->endpoint, 2, devname); + if (ep < 0) + continue; + + if (con_id && strcmp(con->id, con_id)) + continue; + + ret = match(con, !ep, data); + if (ret) + break; + } + + mutex_unlock(&devcon_lock); + + return ret; +} +EXPORT_SYMBOL_GPL(device_connection_find_match); + +extern struct bus_type platform_bus_type; +extern struct bus_type pci_bus_type; +extern struct bus_type i2c_bus_type; +extern struct bus_type spi_bus_type; + +static struct bus_type *generic_match_buses[] = { + &platform_bus_type, +#ifdef CONFIG_PCI + &pci_bus_type, +#endif +#ifdef CONFIG_I2C + &i2c_bus_type, +#endif +#ifdef CONFIG_SPI_MASTER + &spi_bus_type, +#endif + NULL, +}; + +/* This tries to find the device from the most common bus types by name. */ +static void *generic_match(struct device_connection *con, int ep, void *data) +{ + struct bus_type *bus; + struct device *dev; + + for (bus = generic_match_buses[0]; bus; bus++) { + dev = bus_find_device_by_name(bus, NULL, con->endpoint[ep]); + if (dev) + return dev; + } + + /* + * We only get called if a connection was found, tell the caller to + * wait for the other device to show up. + */ + return ERR_PTR(-EPROBE_DEFER); +} + +/** + * device_connection_find - Find two devices connected together + * @dev: Device with the connection + * @con_id: Identifier for the connection + * + * Find a connection with unique identifier @con_id between @dev and + * another device. On success returns handle to the device that is connected + * to @dev, with the reference count for the found device incremented. Returns + * NULL if no matching connection was found, or ERR_PTR(-EPROBE_DEFER) when a + * connection was found but the other device has not been enumerated yet. + */ +struct device *device_connection_find(struct device *dev, const char *con_id) +{ + return device_connection_find_match(dev, con_id, NULL, generic_match); +} +EXPORT_SYMBOL_GPL(device_connection_find); + +/** + * device_connection_add - Register a connection description + * @con: The connection description to be registered + */ +void device_connection_add(struct device_connection *con) +{ + mutex_lock(&devcon_lock); + list_add_tail(&con->list, &devcon_list); + mutex_unlock(&devcon_lock); +} +EXPORT_SYMBOL_GPL(device_connection_add); + +/** + * device_connections_remove - Unregister connection description + * @con: The connection description to be unregistered + */ +void device_connection_remove(struct device_connection *con) +{ + mutex_lock(&devcon_lock); + list_del(&con->list); + mutex_unlock(&devcon_lock); +} +EXPORT_SYMBOL_GPL(device_connection_remove); diff --git a/include/linux/device.h b/include/linux/device.h index b093405ed525..204ff64279fd 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -730,6 +730,28 @@ struct device_dma_parameters { }; /** + * struct device_connection - Device Connection Descriptor + * @endpoint: The names of the two devices connected together + * @id: Unique identifier for the connection + * @list: List head, private, for internal use only + */ +struct device_connection { + const char *endpoint[2]; + const char *id; + struct list_head list; +}; + +void *device_connection_find_match(struct device *dev, const char *con_id, + void *data, + void *(*match)(struct device_connection *con, + int ep, void *data)); + +struct device *device_connection_find(struct device *dev, const char *con_id); + +void device_connection_add(struct device_connection *con); +void device_connection_remove(struct device_connection *con); + +/** * enum device_link_state - Device link states. * @DL_STATE_NONE: The presence of the drivers is not being tracked. * @DL_STATE_DORMANT: None of the supplier/consumer drivers is present. |