drivers: base: Unified device connection lookup

Several frameworks - clk, gpio, phy, pmw, etc. - maintain
lookup tables for describing connections and provide custom
API for handling them. This introduces a single generic
lookup table and API for the connections.

The motivation for this commit is centralizing the
connection lookup, but the goal is to ultimately extract the
connection descriptions also from firmware by using the
fwnode_graph_* functions and other mechanisms that are
available.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Heikki Krogerus 2018-03-20 15:57:02 +03:00 committed by Greg Kroah-Hartman
parent 2699126bcf
commit f2d9b66d84
4 changed files with 203 additions and 1 deletions

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@ -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

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@ -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/

136
drivers/base/devcon.c Normal file
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@ -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);

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@ -729,6 +729,28 @@ struct device_dma_parameters {
unsigned long segment_boundary_mask;
};
/**
* 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.