昨天博文《linux下无线鼠标驱动执行流程》中有一行输出信息很让我迷惑,如下所示:
[ 3597.864715] generic-usb 0003:1D57:0016.0006: input,hidraw2: USB HID v1.10 Mouse [HID Wireless Mouse HID Wireless Mouse] on usb-0000:00:1d.7-1.2/input0
该行信息中最后 "input,hidraw2: USB HID v1.10 Mouse [HID Wireless Mouse HID Wireless Mouse] on usb-0000:00:1d.7-1.2/input0"这一部分内容
对应hid_info的第二个参数(位于drivers/hid/hid-core.c):
hid_info(hdev, "%s: %s HID v%x.%02x %s [%s] on %s ", buf, bus, hdev->version >> 8, hdev->version & 0xff, type, hdev->name, hdev->phys)
但是该行前面的"generic-usb 0003:1D57:0016.0006:"却不知道是从哪儿生成的,因此我想追踪一下hid_info函数的执行过程。
hid_info定义如下(include/linux/hid.h):
#define hid_info(hid, fmt, arg...) dev_info(&(hid)->dev, fmt, ##arg)
而dev_info函数定义如下(include/linux/device.h):
#define dev_info(dev, fmt, arg...) _dev_info(dev, fmt, ##arg)
_dev_info函数定义如下(drivers/base/core.c):
#ifdef CONFIG_PRINTK int __dev_printk(const char *level, const struct device *dev, struct va_format *vaf) { if (!dev) return printk("%s(NULL device *): %pV", level, vaf); return printk("%s%s %s: %pV", level, dev_driver_string(dev), dev_name(dev), vaf); } EXPORT_SYMBOL(__dev_printk); int dev_printk(const char *level, const struct device *dev, const char *fmt, ...) { struct va_format vaf; va_list args; int r; va_start(args, fmt); vaf.fmt = fmt; vaf.va = &args; r = __dev_printk(level, dev, &vaf); va_end(args); return r; } EXPORT_SYMBOL(dev_printk); #define define_dev_printk_level(func, kern_level) int func(const struct device *dev, const char *fmt, ...) { struct va_format vaf; va_list args; int r; va_start(args, fmt); vaf.fmt = fmt; vaf.va = &args; r = __dev_printk(kern_level, dev, &vaf); va_end(args); return r; } EXPORT_SYMBOL(func); define_dev_printk_level(dev_emerg, KERN_EMERG); define_dev_printk_level(dev_alert, KERN_ALERT); define_dev_printk_level(dev_crit, KERN_CRIT); define_dev_printk_level(dev_err, KERN_ERR); define_dev_printk_level(dev_warn, KERN_WARNING); define_dev_printk_level(dev_notice, KERN_NOTICE); define_dev_printk_level(_dev_info, KERN_INFO); #endif
上面这部分函数定义只有在定义CONFIG_PRINTK时才有效,需要查看内核配置文件是否有其定义.
查看当前内核配置:
$uname -a Linux debian 3.2.0-4-686-pae #1 SMP Debian 3.2.54-2 i686 GNU/Linux
查看 /boot/config-3.2.0-4-686-pae文件中确实定义了CONFIG_RPINTK:
CONFIG_PRINTK=y
上面的函数定义实际上就是将最终调用下面内容:
printk("%s%s %s: %pV", KERN_INFO, dev_driver_string(dev), dev_name(dev), vaf);
KERN_INFO定义如下(include/linux/printk.h):
#define KERN_INFO "<6>" /* informational */
dev_driver_string定义如下(drivers/base/core.c):
const char *dev_driver_string(const struct device *dev) { struct device_driver *drv; /* dev->driver can change to NULL underneath us because of unbinding, * so be careful about accessing it. dev->bus and dev->class should * never change once they are set, so they don't need special care. */ drv = ACCESS_ONCE(dev->driver); return drv ? drv->name : (dev->bus ? dev->bus->name : (dev->class ? dev->class->name : "")); } EXPORT_SYMBOL(dev_driver_string);
dev_name函数定义如下(include/linux/device.h):
static inline const char *dev_name(const struct device *dev) { /* Use the init name until the kobject becomes available */ if (dev->init_name) return dev->init_name; return kobject_name(&dev->kobj); }
dev_driver_string获取驱动的字符串,最终使用的驱动是usbhid,其定义如下(drivers/hid/usbhid/hid-core.c):
static struct hid_driver hid_usb_driver = { .name = "generic-usb", .id_table = hid_usb_table, };
所以驱动名称就是generic-usb。
而dev_name中则查看其init_name的值是否为空,如果不为空返回init_name,如果为空,则返回其kobj的名称。
此处init_name为空(默认值为NULL,在源代码中也没有找到相关的赋值),所以使用的是kobj的名称。
在函数hid_add_device(drivers/hid/hid-core.c)中有下面的代码:
dev_set_name(&hdev->dev, "%04X:%04X:%04X.%04X", hdev->bus, hdev->vendor, hdev->product, atomic_inc_return(&id));
该行代码将kobj的值设定成总线、vendor、product以及id连接成的字符串。
从我的前一篇博文中提到vendor和product分别是0x1d57和0x0016,此处使用%04X,那么中间的vendor和product
应该分别是1D57和0016,这与上面的输出信息是一致的。
hid_info函数大致执行流程就这样,但是我还是没弄清楚usbhid和hid模块之间是如何有机联系起来的,等到对usb模块
有了更深入了解后再回头来看二者之间的联系。