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platform 总线上的驱动注册一般使用module_platform_driver宏，如goldfish设备的注册
module_platform_driver(goldfish_pipe);
这个宏定义在/goldfish/include/linux/platform_device.h文件
/* module_platform_driver() - Helper macro for drivers that don't 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_platform_driver(__platform_driver) \
module_driver(__platform_driver, platform_driver_register, \
platform_driver_unregister)
#define module_driver(__driver, __register, __unregister, ...) \
static int __init __driver##_init(void) \
{ \
return __register(&(__driver) , ##__VA_ARGS__); \
} \
module_init(__driver##_init); \
static void __exit __driver##_exit(void) \
{ \
__unregister(&(__driver) , ##__VA_ARGS__); \
} \
module_exit(__driver##_exit);
对于platform类型的驱动以goldfish_pipe为例子展开如下
static int __init goldfish_pipe_init(void)
{
return platform_driver_register(&(goldfish_pipe) );
}
module_init(goldfish_pipe_init);
static void __exit goldfish_pipe_exit(void) \
{
platform_driver_unregister(&(goldfish_pipe) );
}
module_exit(goldfish_pipe_exit);
也就是在.init.setup6段放了连个函数__goldfish_pipe_init和__goldfish_pipe_exit，作用分别是在内核初始化的时候注册该驱动，退出的时候注销该驱动
#define platform_driver_register(drv) \
__platform_driver_register(drv, THIS_MODULE)
/**
* __platform_driver_register - register a driver for platform-level devices
* @drv: platform driver structure
* @owner: owning module/driver
*/
int __platform_driver_register(struct platform_driver *drv,
struct module *owner)
{
drv->driver.owner = owner;
drv->driver.bus = &platform_bus_type;
if (drv->probe)
drv->driver.probe = platform_drv_probe;
if (drv->remove)
drv->driver.remove = platform_drv_remove;
if (drv->shutdown)
drv->driver.shutdown = platform_drv_shutdown;
return driver_register(&drv->driver);
}
__platform_driver_register的函数设置了一些driver的方法，如probe, remove和shutdown,如果用户没有自己设定该方法，就使用platform框架的，这有些面向对象的思想，子类可以使用父类方法，也可以复写父类方法
这里也设置了driver的bus成员，指向了platform_bus_type，设置了一些platform方法后，调用通用的driver_register方法注册驱动
/**
* driver_register - register driver with bus
* @drv: driver to register
*
* We pass off most of the work to the bus_add_driver() call,
* since most of the things we have to do deal with the bus
* structures.
*/
int driver_register(struct device_driver *drv)
{
int ret;
struct device_driver *other;
BUG_ON(!drv->bus->p);
if ((drv->bus->probe && drv->probe) ||
(drv->bus->remove && drv->remove) ||
(drv->bus->shutdown && drv->shutdown))
printk(KERN_WARNING "Driver '%s' needs updating - please use "
"bus_type methods\n", drv->name);
other = driver_find(drv->name, drv->bus);
if (other) {
printk(KERN_ERR "Error: Driver '%s' is already registered, "
"aborting...\n", drv->name);
return -EBUSY;
}
ret = bus_add_driver(drv);
if (ret)
return ret;
ret = driver_add_groups(drv, drv->groups);
if (ret) {
bus_remove_driver(drv);
return ret;
}
kobject_uevent(&drv->p->kobj, KOBJ_ADD);
return ret;
}
１首先检查下设备自己实现的probe，remove,shutdown但是bus也支持probe，remove,shutdown的请款，提示用户升级驱动
２在bus上查找同名drive，如果找到了提示错误（driver_find）
３调用bus_add_driver添加driver到bus上
4 调用driver_add_groups添加到驱动组
５发送uevent add 事件
driver_find函数在drivers/base/driver.c文件下
/**
* driver_find - locate driver on a bus by its name.
* @name: name of the driver.
* @bus: bus to scan for the driver.
*
* Call kset_find_obj() to iterate over list of drivers on
* a bus to find driver by name. Return driver if found.
*
* This routine provides no locking to prevent the driver it returns
* from being unregistered or unloaded while the caller is using it.
* The caller is responsible for preventing this.
*/
struct device_driver *driver_find(const char *name, struct bus_type *bus)
{
struct kobject *k = kset_find_obj(bus->p->drivers_kset, name);
struct driver_private *priv;
if (k) {
/* Drop reference added by kset_find_obj() */
kobject_put(k);
priv = to_driver(k);
return priv->driver;
}
return NULL;
}
在/sys/bus/${bus_name}/drivers对应的kset下查找以驱动为名字的文件
add_driver的实现在drivers/base/bus.c文件
/**
* bus_add_driver - Add a driver to the bus.
* @drv: driver.
*/
int bus_add_driver(struct device_driver *drv)
{
struct bus_type *bus;
struct driver_private *priv;
int error = 0;
bus = bus_get(drv->bus);
if (!bus)
return -EINVAL;
pr_debug("bus: '%s': add driver %s\n", bus->name, drv->name);
priv = kzalloc(sizeof(*priv), GFP_KERNEL);
if (!priv) {
error = -ENOMEM;
goto out_put_bus;
}
klist_init(&priv->klist_devices, NULL, NULL);
priv->driver = drv;
drv->p = priv;
priv->kobj.kset = bus->p->drivers_kset;
error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,
"%s", drv->name);
if (error)
goto out_unregister;
klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);
if (drv->bus->p->drivers_autoprobe) {
error = driver_attach(drv);
if (error)
goto out_unregister;
}
module_add_driver(drv->owner, drv);
error = driver_create_file(drv, &driver_attr_uevent);
if (error) {
printk(KERN_ERR "%s: uevent attr (%s) failed\n",
__func__, drv->name);
}
error = driver_add_groups(drv, bus->drv_groups);
if (error) {
/* How the hell do we get out of this pickle? Give up */
printk(KERN_ERR "%s: driver_create_groups(%s) failed\n",
__func__, drv->name);
}
if (!drv->suppress_bind_attrs) {
error = add_bind_files(drv);
if (error) {
/* Ditto */
printk(KERN_ERR "%s: add_bind_files(%s) failed\n",
__func__, drv->name);
}
}
return 0;
out_unregister:
kobject_put(&priv->kobj);
kfree(drv->p);
drv->p = NULL;
out_put_bus:
bus_put(bus);
return error;
}
该函数实现的功能包含如下
1 创建kobj,在bus对应的driver kset下，如platform的/sys/bus/platform/drivers，名称为该驱动的名称
2 添加到bus->p->klist_drivers 链表中
3 driver_attach 进行device绑定
4 module_add_driver
5 driver_create_file
6 driver_add_groups
7 add_bind_files
driver_attach 是实现在文件drivers/base/dd.c中，
/**
* driver_attach - try to bind driver to devices.
* @drv: driver.
*
* Walk the list of devices that the bus has on it and try to
* match the driver with each one. If driver_probe_device()
* returns 0 and the @dev->driver is set, we've found a
* compatible pair.
*/
int driver_attach(struct device_driver *drv)
{
return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
}
实现很简单，遍历bus->p->klist_devices链表中的device, 执行__driver_attach
__driver_attach也在文件drivers/base/dd.c中，
static int __driver_attach(struct device *dev, void *data)
{
struct device_driver *drv = data;
/*
* Lock device and try to bind to it. We drop the error
* here and always return 0, because we need to keep trying
* to bind to devices and some drivers will return an error
* simply if it didn't support the device.
*
* driver_probe_device() will spit a warning if there
* is an error.
*/
if (!driver_match_device(drv, dev))
return 0;
if (dev->parent) /* Needed for USB */
device_lock(dev->parent);
device_lock(dev);
if (!dev->driver)
driver_probe_device(drv, dev);
device_unlock(dev);
if (dev->parent)
device_unlock(dev->parent);
return 0;
}
static inline int driver_match_device(struct device_driver *drv,
struct device *dev)
{
return drv->bus->match ? drv->bus->match(dev, drv) : 1;
}
driver_match_device函数主要是调用bus的match函数去匹配设备和驱动。 完成匹配之后就调用driver_probe_device触发driver的探测函数
platform bus匹配驱动和设备的函数在文件drivers/base/platform.c中如下
/**
* platform_match - bind platform device to platform driver.
* @dev: device.
* @drv: driver.
*
* Platform device IDs are assumed to be encoded like this:
* "<name><instance>", where <name> is a short description of the type of
* device, like "pci" or "floppy", and <instance> is the enumerated
* instance of the device, like '0' or '42'. Driver IDs are simply
* "<name>". So, extract the <name> from the platform_device structure,
* and compare it against the name of the driver. Return whether they match
* or not.
*/
static int platform_match(struct device *dev, struct device_driver *drv)
{
struct platform_device *pdev = to_platform_device(dev);
struct platform_driver *pdrv = to_platform_driver(drv);
/* When driver_override is set, only bind to the matching driver */
if (pdev->driver_override)
return !strcmp(pdev->driver_override, drv->name);
/* Attempt an OF style match first */
if (of_driver_match_device(dev, drv))
return 1;
/* Then try ACPI style match */
if (acpi_driver_match_device(dev, drv))
return 1;
/* Then try to match against the id table */
if (pdrv->id_table)
return platform_match_id(pdrv->id_table, pdev) != NULL;
/* fall-back to driver name match */
return (strcmp(pdev->name, drv->name) == 0);
}
这部分逻辑可以参考总线驱动设备匹配过程分析这篇文章
匹配成功则代表设备和驱动都存在了，所以就可以进行下一步操作，绑定设备和驱动，是通过函数driver_probe_device完成的
drivers/base/dd.c
/**
* driver_probe_device - attempt to bind device & driver together
* @drv: driver to bind a device to
* @dev: device to try to bind to the driver
*
* This function returns -ENODEV if the device is not registered,
* 1 if the device is bound successfully and 0 otherwise.
*
* This function must be called with @dev lock held. When called for a
* USB interface, @dev->parent lock must be held as well.
*/
int driver_probe_device(struct device_driver *drv, struct device *dev)
{
int ret = 0;
if (!device_is_registered(dev))
return -ENODEV;
pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
drv->bus->name, __func__, dev_name(dev), drv->name);
pm_runtime_barrier(dev);
ret = really_probe(dev, drv);
pm_request_idle(dev);
return ret;
}
1 首先调用device_is_registered确保设备已经注册
2 pm_runtime_barrier防止设备掉电
3 really_probe 真正的探测函数
static int really_probe(struct device *dev, struct device_driver *drv)
{
int ret = 0;
int local_trigger_count = atomic_read(&deferred_trigger_count);
atomic_inc(&probe_count);
pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
drv->bus->name, __func__, drv->name, dev_name(dev));
WARN_ON(!list_empty(&dev->devres_head));
dev->driver = drv;
/* If using pinctrl, bind pins now before probing */
ret = pinctrl_bind_pins(dev);
if (ret)
goto probe_failed;
if (driver_sysfs_add(dev)) {
printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n",
__func__, dev_name(dev));
goto probe_failed;
}
if (dev->bus->probe) {
ret = dev->bus->probe(dev);
if (ret)
goto probe_failed;
} else if (drv->probe) {
ret = drv->probe(dev);
if (ret)
goto probe_failed;
}
driver_bound(dev);
ret = 1;
pr_debug("bus: '%s': %s: bound device %s to driver %s\n",
drv->bus->name, __func__, dev_name(dev), drv->name);
goto done;
probe_failed:
devres_release_all(dev);
driver_sysfs_remove(dev);
dev->driver = NULL;
dev_set_drvdata(dev, NULL);
if (ret == -EPROBE_DEFER) {
/* Driver requested deferred probing */
dev_info(dev, "Driver %s requests probe deferral\n", drv->name);
driver_deferred_probe_add(dev);
/* Did a trigger occur while probing? Need to re-trigger if yes */
if (local_trigger_count != atomic_read(&deferred_trigger_count))
driver_deferred_probe_trigger();
} else if (ret != -ENODEV && ret != -ENXIO) {
/* driver matched but the probe failed */
printk(KERN_WARNING
"%s: probe of %s failed with error %d\n",
drv->name, dev_name(dev), ret);
} else {
pr_debug("%s: probe of %s rejects match %d\n",
drv->name, dev_name(dev), ret);
}
/*
* Ignore errors returned by ->probe so that the next driver can try
* its luck.
*/
ret = 0;
done:
atomic_dec(&probe_count);
wake_up(&probe_waitqueue);
return ret;
}
1 绑定针脚控制器(pinctrl_bind_pins)
2 创建dev设备的sysfs对应目录
3 如果bus存在probe函数调用bus的，否则driver存在probe函数则调用
driver的，由此可见bus的优先级比较高
4 给driver绑定device
5 通知probe_waitqueue
struct bus_type platform_bus_type = {
.name = "platform",
.dev_groups = platform_dev_groups,
.match = platform_match,
.uevent = platform_uevent,
.pm = &platform_dev_pm_ops,
};
platform_bus_type并没有实现自己的probe函数，另外如果driver实现了probe函数，则会被替换为platform_drv_probe函数，所以这里基本上调用的都是platform_drv_probe（除非driver不需要执行probe函数）
static int platform_drv_probe(struct device *_dev)
{
struct platform_driver *drv = to_platform_driver(_dev->driver);
struct platform_device *dev = to_platform_device(_dev);
int ret;
ret = of_clk_set_defaults(_dev->of_node, false);
if (ret < 0)
return ret;
ret = dev_pm_domain_attach(_dev, true);
if (ret != -EPROBE_DEFER) {
ret = drv->probe(dev);
if (ret)
dev_pm_domain_detach(_dev, true);
}
if (drv->prevent_deferred_probe && ret == -EPROBE_DEFER) {
dev_warn(_dev, "probe deferral not supported\n");
ret = -ENXIO;
}
return ret;
}
1 of_clk_set_defaults 用于设置时钟信息
2 dev_pm_domain_attach用于附加到电源管理域上
3 调用driver自己实现的prob函数
我们以goldfish_pipe为例子看下是如何实现的probe函数
drivers/platform/goldfish/goldfish_pipe.c
static int goldfish_pipe_probe(struct platform_device *pdev)
{
DPRINT("%s: call. platform_device=0x%lx\n", __FUNCTION__, pdev);
int err;
struct resource *r;
struct goldfish_pipe_dev *dev = pipe_dev;
/* not thread safe, but this should not happen */
WARN_ON(dev->base != NULL);
spin_lock_init(&dev->lock);
r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (r == NULL || resource_size(r) < PAGE_SIZE) {
dev_err(&pdev->dev, "can't allocate i/o page\n");
return -EINVAL;
}
dev->base = devm_ioremap(&pdev->dev, r->start, PAGE_SIZE);
if (dev->base == NULL) {
dev_err(&pdev->dev, "ioremap failed\n");
return -EINVAL;
}
r = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
if (r == NULL) {
err = -EINVAL;
goto error;
}
dev->irq = r->start;
err = devm_request_irq(&pdev->dev, dev->irq, goldfish_pipe_interrupt,
IRQF_SHARED, "goldfish_pipe", dev);
if (err) {
dev_err(&pdev->dev, "unable to allocate IRQ\n");
goto error;
}
err = misc_register(&goldfish_pipe_device);
if (err) {
dev_err(&pdev->dev, "unable to register device\n");
goto error;
}
setup_access_params_addr(pdev, dev);
/* Although the pipe device in the classic Android emulator does not
* recognize the 'version' register, it won't treat this as an error
* either and will simply return 0, which is fine. */
dev->version = readl(dev->base + PIPE_REG_VERSION);
return 0;
error:
dev->base = NULL;
return err;
}
1 获取设备=io地址空间（物理地址）
2 使用ioremap映射到一块虚拟地址
3 获取irq信息，注册irq处理函数 goldfish_pipe_interrupt
4 注册为设备goldfish_pipe_device
driver和device匹配到后就会执行module_add_driver， 这部分主要创建/sys/module下的kobject目录，注册irq处理函数
void module_add_driver(struct module *mod, struct device_driver *drv)
{
char *driver_name;
int no_warn;
struct module_kobject *mk = NULL;
if (!drv)
return;
if (mod)
mk = &mod->mkobj;
else if (drv->mod_name) {
struct kobject *mkobj;
/* Lookup built-in module entry in /sys/modules */
mkobj = kset_find_obj(module_kset, drv->mod_name);
if (mkobj) {
mk = container_of(mkobj, struct module_kobject, kobj);
/* remember our module structure */
drv->p->mkobj = mk;
/* kset_find_obj took a reference */
kobject_put(mkobj);
}
}
if (!mk)
return;
/* Don't check return codes; these calls are idempotent */
no_warn = sysfs_create_link(&drv->p->kobj, &mk->kobj, "module");
driver_name = make_driver_name(drv);
if (driver_name) {
module_create_drivers_dir(mk);
no_warn = sysfs_create_link(mk->drivers_dir, &drv->p->kobj,
driver_name);
kfree(driver_name);
}
}
创建不创建对应的module模块还要看mk参数是否为空，不为空的情况下会把/sys/module/${driver_module} 目录符号链接到/sys/bus/${bus_name}/drivers/${driver_name}/module目录，给用户提供一个视角, 并在/sys/module下创建driver相关文件夹,下面的文件也是从/sys/bus/${bus_name}/drivers/${driver_name}链接过来的
driver_create_file 创建uevent文件，用于发送uevent事件
driver_add_groups 创建这个组
int driver_add_groups(struct device_driver *drv,
const struct attribute_group **groups)
{
return sysfs_create_groups(&drv->p->kobj, groups);
}
/**
* driver_probe_device - attempt to bind device & driver together
* @drv: driver to bind a device to
* @dev: device to try to bind to the driver
*
* This function returns -ENODEV if the device is not registered,
* 1 if the device is bound successfully and 0 otherwise.
*
* This function must be called with @dev lock held. When called for a
* USB interface, @dev->parent lock must be held as well.
*/
int driver_probe_device(struct device_driver *drv, struct device *dev)
{
int ret = 0;
if (!device_is_registered(dev))
return -ENODEV;
pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
drv->bus->name, __func__, dev_name(dev), drv->name);
pm_runtime_barrier(dev);
ret = really_probe(dev, drv);
pm_request_idle(dev);
return ret;
}
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