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在Linux2.6以后的設(shè)備驅(qū)動模型中，需關(guān)心總線，設(shè)備和驅(qū)動這三種實(shí)體，總線將設(shè)備和驅(qū)動綁定。在系統(tǒng)每注冊一個(gè)設(shè)備的時(shí)候，會尋找與之匹配的驅(qū)動；相反，在系統(tǒng)每注冊一個(gè)驅(qū)動的時(shí)候，會尋找與之匹配的設(shè)備，而匹配由總線完成。?
對于依附在USB、PCI、I2C、SPI等物理總線來 這些都不是問題。但是在嵌入式系統(tǒng)里面，在Soc系統(tǒng)中集成的獨(dú)立外設(shè)控制器，掛接在Soc內(nèi)存空間的外設(shè)等卻不依附在此類總線。基于這一背景，Linux發(fā)明了一種總線，稱為platform。?
相對于USB、PCI、I2C、SPI等物理總線來說，platform總線是一種虛擬、抽象出來的總線，實(shí)際中并不存在這樣的總線。?
platform總線相關(guān)代碼：driveraseplatform.c 文件?
相關(guān)結(jié)構(gòu)體定義：includelinuxplatform_device.h 文件中
platform總線管理下最重要的兩個(gè)結(jié)構(gòu)體是platform_device和platform_driver?
分別表示設(shè)備和驅(qū)動?
在Linux中的定義如下?
一：platform_driver
//includelinuxplatform_device.h struct platform_driver { int (*probe)(struct platform_device *); //探測函數(shù)，在注冊平臺設(shè)備時(shí)被調(diào)用 int (*remove)(struct platform_device *); //刪除函數(shù)，在注銷平臺設(shè)備時(shí)被調(diào)用 void (*shutdown)(struct platform_device *); int (*suspend)(struct platform_device *, pm_message_t state); //掛起函數(shù)，在關(guān)機(jī)被調(diào)用 int (*suspend_late)(struct platform_device *, pm_message_t state); int (*resume_early)(struct platform_device *); int (*resume)(struct platform_device *);//恢復(fù)函數(shù)，在開機(jī)時(shí)被調(diào)用 struct device_driver driver;//設(shè)備驅(qū)動結(jié)構(gòu)};
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struct device_driver { const char * name; struct bus_type * bus; struct kobject kobj; struct klist klist_devices; struct klist_node knode_bus; struct module * owner; const char * mod_name; /* used for built-in modules */ struct module_kobject * mkobj; int (*probe) (struct device * dev); int (*remove) (struct device * dev); void (*shutdown) (struct device * dev); int (*suspend) (struct device * dev, pm_message_t state); int (*resume) (struct device * dev);};
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二：platform_device
struct platform_device { const char * name;//設(shè)備名稱 u32 id;//取-1 struct device dev;//設(shè)備結(jié)構(gòu) u32 num_resources;// resource結(jié)構(gòu)個(gè)數(shù) struct resource * resource;//設(shè)備資源};
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resource結(jié)構(gòu)體也是描述platform_device的一個(gè)重要結(jié)構(gòu)體 該元素存入了最為重要的設(shè)備資源信息
struct resource { resource_size_t start; resource_size_t end; const char *name; unsigned long flags; struct resource *parent, *sibling, *child;};
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我們通常關(guān)心start，end，flags。它們分別標(biāo)明了資源的開始值，結(jié)束值和類型，flags可以為IORESOURCE_IO,IORESOURCE_MEM,IORESOURCE_IRQ,IORESOURCE_DMA等，start,end的含義會隨著flags變更，如當(dāng)flags為IORESOURCE_MEM時(shí)，start,end分別表示該platform_device占據(jù)的內(nèi)存的開始地址和結(jié)束地址；當(dāng)flags為,IORESOURCE_IRQ時(shí)，start,end分別表示該platform_device使用的中斷號的開始值和結(jié)束值，如果只使用了1個(gè)中斷號，開始和結(jié)束值相同。對于同種類型的資源而言，可以有多份，例如某設(shè)備占據(jù)了兩個(gè)內(nèi)存區(qū)域，則可以定義兩個(gè)IORESOURCE_MEM資源。? 對resource的定義也通常在BSP的板文件中運(yùn)行，而在具體的設(shè)備驅(qū)動中通過platform_get_resource()這樣的API來獲取，此API的原型為：
struct resource *platform_get_resource(struct platform_device *dev， unsigned int type,unsigned int num)
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例如在archarmmach-at91Board-sam9261ek.c板文件中為DM9000網(wǎng)卡定義了如下的resource
static struct resource at91sam9261_dm9000_resource[] = { [0] = { .start = AT91_CHIPSELECT_2, .end = AT91_CHIPSELECT_2 + 3, .flags = IORESOURCE_MEM }, [1] = { .start = AT91_CHIPSELECT_2 + 0x44, .end = AT91_CHIPSELECT_2 + 0xFF, .flags = IORESOURCE_MEM }, [2] = { .start = AT91_PIN_PC11, .end = AT91_PIN_PC11, .flags = IORESOURCE_IRQ }};
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在DM9000網(wǎng)卡驅(qū)動中則是通過如下辦法拿到這3份資源
db->addr_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);db->data_res = platform_get_resource(pdev, IORESOURCE_MEM, 1);db->irq_res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
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對于irq而言platform_get_resource()還有一個(gè)進(jìn)行了封裝的變體platform_get_irq(),? api原型是
int platform_get_irq(struct platform_device *dev, unsigned int num){ struct resource *r = platform_get_resource(dev, IORESOURCE_IRQ, num); return r ? r->start : -ENXIO;}
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實(shí)際上這個(gè)函數(shù)也是調(diào)用platform_get_resource(dev, IORESOURCE_IRQ, num)來獲取資源
設(shè)備除了可以在BSP中定義資源以外，還可以附加一些數(shù)據(jù)信息，因?yàn)閷υO(shè)備的硬件描述除了中斷，內(nèi)存等標(biāo)準(zhǔn)資源以外，可能還會有一些配置信息，這些配置信息也依賴于板，不適宜直接放置在設(shè)備驅(qū)動上，因此，platform也提供了platform_data的支持，例如對于dm9000
static struct dm9000_plat_data dm9000_platdata = { .flags = DM9000_PLATF_16BITONLY,};static struct platform_device at91sam9261_dm9000_device = { .name = "dm9000", .id = 0, .num_resources = ARRAY_SIZE(at91sam9261_dm9000_resource), .resource = at91sam9261_dm9000_resource, .dev = { .platform_data = &dm9000_platdata, }};
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獲取platform_data的API是dev_get_platdata()
struct dm9000_plat_data *pdata = dev_get_platdata(&pdev->dev);
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三：platform總線? 系統(tǒng)為platform總線定義了一個(gè)bus_type的實(shí)例platform_bus_type，其定義位于drivers/base/platform.c下
struct bus_type platform_bus_type = { .name = "platform", .dev_attrs = platform_dev_attrs, .match = platform_match, .uevent = platform_uevent, .pm = &platform_dev_pm_ops,};
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最重要的是match函數(shù)，真是此成員函數(shù)確定了platform_device和platform_driver之間如何匹配的
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); /* Attempt an OF style match first */ if (of_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);}
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可知有3中情況下platform_device和platform_driver匹配? 1.基于設(shè)備樹風(fēng)格的匹配? 2.匹配ID表(即platform_device設(shè)備名是否出現(xiàn)在platform_driver的id表內(nèi))? 3.匹配platform_device設(shè)備名和驅(qū)動的名字? 在4.0還有一種情況是基于ACPI風(fēng)格的匹配
對于設(shè)備驅(qū)動的開發(fā)? 其設(shè)計(jì)順序?yàn)槎x platform_device -> 注冊 platform_device-> 定義 platform_driver-> 注冊 platform_driver 。? 這里選用的例子是q40kbd，在/drivers/input/serio目錄里。這是一個(gè)鍵盤控制器驅(qū)動? 這里直接分析初始化函數(shù)
static int __init q40kbd_init(void){ int error; if (!MACH_IS_Q40) return -EIO; /* platform總線驅(qū)動的注冊 */ error = platform_driver_register(&q40kbd_driver); if (error) return error; /* 分配一個(gè)platform設(shè)備 */ q40kbd_device = platform_device_alloc("q40kbd", -1); if (!q40kbd_device) goto err_unregister_driver; /* platform設(shè)備注冊 */ error = platform_device_add(q40kbd_device); if (error) goto err_free_device; return 0; err_free_device: platform_device_put(q40kbd_device); err_unregister_driver: platform_driver_unregister(&q40kbd_driver); return error;}
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驅(qū)動注冊函數(shù)是 platform_driver_register()函數(shù)
int platform_driver_register(struct platform_driver *drv){ //把驅(qū)動的總線設(shè)置為platform總線 drv->driver.bus = &platform_bus_type; //依次設(shè)置驅(qū)動的各個(gè)函數(shù)指針 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; if (drv->suspend) drv->driver.suspend = platform_drv_suspend; if (drv->resume) drv->driver.resume = platform_drv_resume; //調(diào)用driver_register注冊驅(qū)動 return driver_register(&drv->driver);}
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/* 初始化后調(diào)用bus_add_driver函數(shù)執(zhí)行注冊過程 */int driver_register(struct device_driver * drv){ 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 ", drv->name); } klist_init(&drv->klist_devices, NULL, NULL); return bus_add_driver(drv);}
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為總線增加一個(gè)驅(qū)動
int bus_add_driver(struct device_driver *drv){ struct bus_type * bus = get_bus(drv->bus); int error = 0; if (!bus) return -EINVAL; pr_debug("bus %s: add driver %s ", bus->name, drv->name); /* 為kobject結(jié)構(gòu)設(shè)置名字 */ error = kobject_set_name(&drv->kobj, "%s", drv->name); if (error) goto out_put_bus; drv->kobj.kset = &bus->drivers; /* 為sysfs文件系統(tǒng)創(chuàng)建設(shè)備的相關(guān)文件 */ if ((error = kobject_register(&drv->kobj))) goto out_put_bus; if (drv->bus->drivers_autoprobe) { /* 驅(qū)動加入總線的驅(qū)動列表 */ error = driver_attach(drv); if (error) goto out_unregister; } /* 在sysfs創(chuàng)建驅(qū)動的屬性文件和模塊 */ klist_add_tail(&drv->knode_bus, &bus->klist_drivers); module_add_driver(drv->owner, drv); error = driver_add_attrs(bus, drv); if (error) { /* How the hell do we get out of this pickle? Give up */ printk(KERN_ERR "%s: driver_add_attrs(%s) failed ", __FUNCTION__, drv->name); } error = add_bind_files(drv); if (error) { /* Ditto */ printk(KERN_ERR "%s: add_bind_files(%s) failed ", __FUNCTION__, drv->name); } return error;out_unregister: kobject_unregister(&drv->kobj);out_put_bus: put_bus(bus); return error;}
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執(zhí)行驅(qū)動加載
int driver_attach(struct device_driver * drv){ return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);}int bus_for_each_dev(struct bus_type * bus, struct device * start, void * data, int (*fn)(struct device *, void *)){ struct klist_iter i; struct device * dev; int error = 0; if (!bus) return -EINVAL; /* 初始化一個(gè)klist_iter結(jié)構(gòu) 目的是在雙向鏈表中定位一個(gè)成員 */ klist_iter_init_node(&bus->klist_devices, &i, (start ? &start->knode_bus : NULL)); while ((dev = next_device(&i)) && !error) //對每個(gè)設(shè)備都調(diào)用fn函數(shù)指針 fn就是傳入的函數(shù)指針__driver_attach error = fn(dev, data); klist_iter_exit(&i); return error;}
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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 (dev->parent) /* Needed for USB */ down(&dev->parent->sem); /* 獲取設(shè)備的鎖 */ down(&dev->sem); if (!dev->driver) driver_probe_device(drv, dev); up(&dev->sem); if (dev->parent) up(&dev->parent->sem); return 0;}
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int driver_probe_device(struct device_driver * drv, struct device * dev){ int ret = 0; if (!device_is_registered(dev)) return -ENODEV; /* 調(diào)用總線配置的match函數(shù) */ if (drv->bus->match && !drv->bus->match(dev, drv)) goto done; pr_debug("%s: Matched Device %s with Driver %s ", drv->bus->name, dev->bus_id, drv->name); /* 調(diào)用really_probe函數(shù) */ ret = really_probe(dev, drv);done: return ret;}static int really_probe(struct device *dev, struct device_driver *drv){ int ret = 0; atomic_inc(&probe_count); pr_debug("%s: Probing driver %s with device %s ", drv->bus->name, drv->name, dev->bus_id); WARN_ON(!list_empty(&dev->devres_head)); dev->driver = drv; if (driver_sysfs_add(dev)) { printk(KERN_ERR "%s: driver_sysfs_add(%s) failed ", __FUNCTION__, dev->bus_id); goto probe_failed; } /* 調(diào)用總線的probe函數(shù) */ if (dev->bus->probe) { ret = dev->bus->probe(dev); if (ret) goto probe_failed; /* 如果驅(qū)動提供了Probe函數(shù)，則調(diào)用驅(qū)動的probe函數(shù) */ } else if (drv->probe) { ret = drv->probe(dev); if (ret) goto probe_failed; } /* 設(shè)備發(fā)現(xiàn)了驅(qū)動 通過sysfs創(chuàng)建一些文件 和設(shè)備做符號鏈接 */ driver_bound(dev); ret = 1; pr_debug("%s: Bound Device %s to Driver %s ", drv->bus->name, dev->bus_id, drv->name); goto done;probe_failed: devres_release_all(dev); driver_sysfs_remove(dev); dev->driver = NULL; if (ret != -ENODEV && ret != -ENXIO) { /* driver matched but the probe failed */ printk(KERN_WARNING "%s: probe of %s failed with error %d ", drv->name, dev->bus_id, 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;}
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driver_probe_device() 這個(gè)函數(shù)實(shí)際上做了兩件事? 1.調(diào)用總線提供的match函數(shù)。如果檢查通過 說明設(shè)備和驅(qū)動是匹配的 設(shè)備所指的驅(qū)動指針要賦值為當(dāng)前驅(qū)動? 2.探測(probe) 首先調(diào)用總線提供的probe函數(shù)，如果驅(qū)動有自己的Probe函數(shù)，還要調(diào)用驅(qū)動的probe函數(shù)
platform總線的match函數(shù)在上文有介紹 三種情況均可匹配? platform總線的probe函數(shù)就是platform_drv_probe() 這個(gè)函數(shù)是個(gè)封裝函數(shù) 它只是簡單的調(diào)用了驅(qū)動的Probe函數(shù) 驅(qū)動的Probe函數(shù)就是q40kbd_probe
static int __devinit q40kbd_probe(struct platform_device *dev){ q40kbd_port = kzalloc(sizeof(struct serio), GFP_KERNEL); if (!q40kbd_port) return -ENOMEM; q40kbd_port->id.type = SERIO_8042; q40kbd_port->open = q40kbd_open; q40kbd_port->close = q40kbd_close; q40kbd_port->dev.parent = &dev->dev; strlcpy(q40kbd_port->name, "Q40 Kbd Port", sizeof(q40kbd_port->name)); strlcpy(q40kbd_port->phys, "Q40", sizeof(q40kbd_port->phys)); //注冊serio結(jié)構(gòu)變量 serio_register_port(q40kbd_port); printk(KERN_INFO "serio: Q40 kbd registered "); return 0;}
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綜上所述，platform總線驅(qū)動注冊就是遍歷各個(gè)設(shè)備 檢查是否和驅(qū)動匹配
接下來分析platform設(shè)備的注冊
int platform_device_add(struct platform_device *pdev){ int i, ret = 0; if (!pdev) return -EINVAL; /* 設(shè)置設(shè)備的父類型 */ if (!pdev->dev.parent) pdev->dev.parent = &platform_bus; /* 設(shè)置設(shè)備的總線類型為platform_bus_type */ pdev->dev.bus = &platform_bus_type; if (pdev->id != -1) snprintf(pdev->dev.bus_id, BUS_ID_SIZE, "%s.%u", pdev->name, pdev->id); else strlcpy(pdev->dev.bus_id, pdev->name, BUS_ID_SIZE); /* 把設(shè)備IO端口和IO內(nèi)存資源注冊到系統(tǒng) */ for (i = 0; i < pdev->num_resources; i++) { struct resource *p, *r = &pdev->resource[i]; if (r->name == NULL) r->name = pdev->dev.bus_id; p = r->parent; if (!p) { if (r->flags & IORESOURCE_MEM) p = &iomem_resource; else if (r->flags & IORESOURCE_IO) p = &ioport_resource; } if (p && insert_resource(p, r)) { printk(KERN_ERR "%s: failed to claim resource %d ", pdev->dev.bus_id, i); ret = -EBUSY; goto failed; } } pr_debug("Registering platform device '%s'. Parent at %s ", pdev->dev.bus_id, pdev->dev.parent->bus_id); ret = device_add(&pdev->dev); if (ret == 0) return ret; failed: while (--i >= 0) if (pdev->resource[i].flags & (IORESOURCE_MEM|IORESOURCE_IO)) release_resource(&pdev->resource[i]); return ret;}
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int device_add(struct device *dev){ struct device *parent = NULL; char *class_name = NULL; struct class_interface *class_intf; int error = -EINVAL; dev = get_device(dev); if (!dev || !strlen(dev->bus_id)) goto Error; pr_debug("DEV: registering device: ID = '%s' ", dev->bus_id); /* 獲得父設(shè)備 */ parent = get_device(dev->parent); error = setup_parent(dev, parent); if (error) goto Error; /* first, register with generic layer. */ /* 這是kobject的名字 */ kobject_set_name(&dev->kobj, "%s", dev->bus_id); /* 在sys目錄生成設(shè)備目錄 */ error = kobject_add(&dev->kobj); if (error) goto Error; /* notify platform of device entry */ if (platform_notify) platform_notify(dev); /* notify clients of device entry (new way) */ if (dev->bus) blocking_notifier_call_chain(&dev->bus->bus_notifier, BUS_NOTIFY_ADD_DEVICE, dev); /* 設(shè)置uevent屬性 */ dev->uevent_attr.attr.name = "uevent"; dev->uevent_attr.attr.mode = S_IRUGO | S_IWUSR; if (dev->driver) dev->uevent_attr.attr.owner = dev->driver->owner; dev->uevent_attr.store = store_uevent; dev->uevent_attr.show = show_uevent; error = device_create_file(dev, &dev->uevent_attr); if (error) goto attrError; /* 設(shè)備的屬性文件 */ if (MAJOR(dev->devt)) { struct device_attribute *attr; attr = kzalloc(sizeof(*attr), GFP_KERNEL); if (!attr) { error = -ENOMEM; goto ueventattrError; } attr->attr.name = "dev"; attr->attr.mode = S_IRUGO; if (dev->driver) attr->attr.owner = dev->driver->owner; attr->show = show_dev; error = device_create_file(dev, attr); if (error) { kfree(attr); goto ueventattrError; } dev->devt_attr = attr; } /* 創(chuàng)建設(shè)備類的符號鏈接 */ if (dev->class) { sysfs_create_link(&dev->kobj, &dev->class->subsys.kobj, "subsystem"); /* If this is not a "fake" compatible device, then create the * symlink from the class to the device. */ if (dev->kobj.parent != &dev->class->subsys.kobj) sysfs_create_link(&dev->class->subsys.kobj, &dev->kobj, dev->bus_id); if (parent) { sysfs_create_link(&dev->kobj, &dev->parent->kobj, "device");#ifdef CONFIG_SYSFS_DEPRECATED class_name = make_class_name(dev->class->name, &dev->kobj); if (class_name) sysfs_create_link(&dev->parent->kobj, &dev->kobj, class_name);#endif } } /* 設(shè)備的能源管理 */ if ((error = device_add_attrs(dev))) goto AttrsError; if ((error = device_pm_add(dev))) goto PMError; if ((error = bus_add_device(dev))) goto BusError; kobject_uevent(&dev->kobj, KOBJ_ADD); bus_attach_device(dev); /* 設(shè)備加入父設(shè)備的鏈表 */ if (parent) klist_add_tail(&dev->knode_parent, &parent->klist_children); if (dev->class) { down(&dev->class->sem); /* tie the class to the device */ list_add_tail(&dev->node, &dev->class->devices); /* notify any interfaces that the device is here */ list_for_each_entry(class_intf, &dev->class->interfaces, node) if (class_intf->add_dev) class_intf->add_dev(dev, class_intf); up(&dev->class->sem); } Done: kfree(class_name); put_device(dev); return error; BusError: device_pm_remove(dev); PMError: if (dev->bus) blocking_notifier_call_chain(&dev->bus->bus_notifier, BUS_NOTIFY_DEL_DEVICE, dev); device_remove_attrs(dev); AttrsError: if (dev->devt_attr) { device_remove_file(dev, dev->devt_attr); kfree(dev->devt_attr); } if (dev->class) { sysfs_remove_link(&dev->kobj, "subsystem"); /* If this is not a "fake" compatible device, remove the * symlink from the class to the device. */ if (dev->kobj.parent != &dev->class->subsys.kobj) sysfs_remove_link(&dev->class->subsys.kobj, dev->bus_id); if (parent) {#ifdef CONFIG_SYSFS_DEPRECATED char *class_name = make_class_name(dev->class->name, &dev->kobj); if (class_name) sysfs_remove_link(&dev->parent->kobj, class_name); kfree(class_name);#endif sysfs_remove_link(&dev->kobj, "device"); } } ueventattrError: device_remove_file(dev, &dev->uevent_attr); attrError: kobject_uevent(&dev->kobj, KOBJ_REMOVE); kobject_del(&dev->kobj); Error: if (parent) put_device(parent); goto Done;}
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遍歷驅(qū)動 為設(shè)備找到合適的驅(qū)動
int device_attach(struct device * dev){ int ret = 0; down(&dev->sem); if (dev->driver) { ret = device_bind_driver(dev); if (ret == 0) ret = 1; else { dev->driver = NULL; ret = 0; } } else { ret = bus_for_each_drv(dev->bus, NULL, dev, __device_attach); } up(&dev->sem); return ret;}
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但是在Linux加入了設(shè)備樹的時(shí)候 就不再需要大量的板級信息了 譬如/arch/arm/plat-xxx和arch/arm/mach-xxx中platform的修改部分? 原先的
static struct resource xxx_resource[] = { [0] = { .start = ..., .end = ..., .flags = ..., }, [1] = { .start = ..., .end = ..., .flags = ..., }, [2] = { .start =..., .end = ..., .flags = ..., }};static struct platform_device xxx_device = { .name = "xxx", .id = -1, .num_resources = ARRAY_SIZE(xxx_resource), .resource = xxx_resource, .dev = { .platform_data = &xxx_platdata, }};
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之類的注冊platform_device,綁定resource,即內(nèi)存，irq等板級信息 現(xiàn)在都不再需要 其中platform_device會由內(nèi)核自動展開。而這些resource實(shí)際來源于.dts中設(shè)備節(jié)點(diǎn)的reg,interrups屬性
再者就是platform_data這些平臺數(shù)據(jù)屬性化? 比如linux-3.4.2archarmmach-at91Board-sam9263ek.c下用如下代碼注冊gpio_keys設(shè)備 通過gpio_keys_platform_data來定義platform_data
static struct gpio_keys_button ek_buttons[] = { { /* BP1, "leftclic" */ .code = BTN_LEFT, .gpio = AT91_PIN_PC5, .active_low = 1, .desc = "left_click", .wakeup = 1, }, { /* BP2, "rightclic" */ .code = BTN_RIGHT, .gpio = AT91_PIN_PC4, .active_low = 1, .desc = "right_click", .wakeup = 1, }};static struct gpio_keys_platform_data ek_button_data = { .buttons = ek_buttons, .nbuttons = ARRAY_SIZE(ek_buttons),};static struct platform_device ek_button_device = { .name = "gpio-keys", .id = -1, .num_resources = 0, .dev = { .platform_data = &ek_button_data, }};
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設(shè)備驅(qū)動drivers/input/keyboard/gpio_keys.c通過以下方法取得這個(gè)platform_data
struct device *dev = &pdev->dev;const struct gpio_keys_platform_data *pdata = dev_get_platdata(dev);
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轉(zhuǎn)移到設(shè)備樹后 platform_data就不再arch/arm/mach-xxx中 它需要從設(shè)備樹中獲取，比如一個(gè)電路板上有g(shù)pio_keys 則只需要在設(shè)備樹中添加類似arch/arm/boot/dts/exyons4210-origen.dts的代碼
gpio_keys { compatible = "gpio-keys"; #address-cells = <1>; #size-cells = <0>; up { label = "Up"; gpios = <&gpx2 0 0 0 2>; linux,code = <103>; }; down { label = "Down"; gpios = <&gpx2 1 0 0 2>; linux,code = <108>; };
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而在驅(qū)動中通過of_開頭的讀屬性的API來讀取這些信息 并組織處gpio_keys_platform_data結(jié)構(gòu)體
gpio_keys_get_devtree_pdata(struct device *dev){ struct gpio_keys_platform_data *pdata; struct gpio_keys_button *button; struct fwnode_handle *child; int nbuttons; nbuttons = device_get_child_node_count(dev); if (nbuttons == 0) return ERR_PTR(-ENODEV); pdata = devm_kzalloc(dev, sizeof(*pdata) + nbuttons * sizeof(*button), GFP_KERNEL); if (!pdata) return ERR_PTR(-ENOMEM); button = (struct gpio_keys_button *)(pdata + 1); pdata->buttons = button; pdata->nbuttons = nbuttons; pdata->rep = device_property_read_bool(dev, "autorepeat"); device_property_read_string(dev, "label", &pdata->name); device_for_each_child_node(dev, child) { if (is_of_node(child)) button->irq = irq_of_parse_and_map(to_of_node(child), 0); if (fwnode_property_read_u32(child, "linux,code", &button->code)) { dev_err(dev, "Button without keycode
"); fwnode_handle_put(child); return ERR_PTR(-EINVAL); } fwnode_property_read_string(child, "label", &button->desc); if (fwnode_property_read_u32(child, "linux,input-type", &button->type)) button->type = EV_KEY; button->wakeup = fwnode_property_read_bool(child, "wakeup-source") || /* legacy name */ fwnode_property_read_bool(child, "gpio-key,wakeup"); button->can_disable = fwnode_property_read_bool(child, "linux,can-disable"); if (fwnode_property_read_u32(child, "debounce-interval", &button->debounce_interval)) button->debounce_interval = 5; button++; } return pdata;}
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