U-Boot的设备管理

目录

一、初始设备链表、初始化设备和注册设备
1.1 devices_init函数
1.2 devices结构的定义
1.3 drv_system_init 函数
二、设备注册
2.1 device_register (device_t * dev)
2.2 device_deregister(char *devname)
三、设备搜索

U-Boot通过devices_init函数创建设备链表，然后在devices_init函数中初始化设备并将设备添加到设备链表中。U-Boot使用devices_t结构体来管理设备，设备链表也就是devices_t结构体的链表。通过i2c_init、drv_lcd_init、drv_video_init、drv_keyboard_init、drv_logbuff_init、drv_system_init、serial_devices_init、drv_usbtty_init和drv_nc_init函数初始化设备(这些函数是否执行是通过宏来决定的)，并通过device_register函数注册设备。

一、初始设备链表、初始化设备和注册设备

U-Boot在第二阶段中通过devices_init函数创建设备链表，初始化设备并将其注册到设备链表中。该函数在common/devices.c文件中，其对应的头文件是nclude/devices.h。

1.1 devices_init函数

int devices_init (void)
{
#ifndef CONFIG_ARM     /* already relocated for current ARM implementation */
	ulong relocation_offset = gd->reloc_off;
	int i;

	/* relocate device name pointers */
	for (i = 0; i < (sizeof (stdio_names) / sizeof (char *)); ++i) {
		stdio_names[i] = (char *) (((ulong) stdio_names[i]) +
						relocation_offset);
	}
#endif

	/* Initialize the list */
	devlist = ListCreate (sizeof (device_t));//创建设备列表

	if (devlist == NULL) {
		eputs ("Cannot initialize the list of devices!\n");
		return -1;
	}
#if defined(CONFIG_HARD_I2C) || defined(CONFIG_SOFT_I2C)
	i2c_init (CFG_I2C_SPEED, CFG_I2C_SLAVE);//初始化i2c接口，i2c没有注册到devlist中去
#endif
#ifdef CONFIG_LCD
	drv_lcd_init ();
#endif
#if defined(CONFIG_VIDEO) || defined(CONFIG_CFB_CONSOLE)
	drv_video_init ();
#endif
#ifdef CONFIG_KEYBOARD
	drv_keyboard_init ();
#endif
#ifdef CONFIG_LOGBUFFER
	drv_logbuff_init ();
#endif
	drv_system_init ();//这里其实是定义了一个串口设备，并且注册到devlist中
#ifdef CONFIG_SERIAL_MULTI
	serial_devices_init ();
#endif
#ifdef CONFIG_USB_TTY
	drv_usbtty_init ();
#endif
#ifdef CONFIG_NETCONSOLE
	drv_nc_init ();
#endif

	return (0);
}

经过devices_init()，创建了devlist，但是只有一个串口设备注册在内。

1.2 devices结构的定义

/* Device information */
typedef struct {
	int	flags;			/* Device flags: input/output/system	*/
	int	ext;			/* Supported extensions			*/
	char	name[16];		/* Device name	设备名称			*/

/* GENERAL functions 启动和停止函数 */

	int (*start) (void);		/* To start the device			*/
	int (*stop) (void);		/* To stop the device			*/

/* OUTPUT functions 输出函数 */

	void (*putc) (const char c);	/* To put a char			*/
	void (*puts) (const char *s);	/* To put a string (accelerator)	*/

/* INPUT functions  输入函数*/

	int (*tstc) (void);		/* To test if a char is ready...	*/
	int (*getc) (void);		/* To get that char			*/

/* Other functions */

	void *priv;			/* Private extensions			*/
} device_t;

1.3 drv_system_init 函数

drv_system_init 函数初始化串口设备，源码如下：

static void drv_system_init (void)
{
	device_t dev;//定义一个结构体

	memset (&dev, 0, sizeof (dev));//为刚刚定义的结构体分配内存

	strcpy (dev.name, "serial");//名称
	dev.flags = DEV_FLAGS_OUTPUT | DEV_FLAGS_INPUT | DEV_FLAGS_SYSTEM; 

#ifdef CONFIG_SERIAL_SOFTWARE_FIFO
	dev.putc = serial_buffered_putc;
	dev.puts = serial_buffered_puts;
	dev.getc = serial_buffered_getc;
	dev.tstc = serial_buffered_tstc;
#else
	dev.putc = serial_putc;
	dev.puts = serial_puts;
	dev.getc = serial_getc;
	dev.tstc = serial_tstc;
#endif

	device_register (&dev);//注册函数

#ifdef CFG_DEVICE_NULLDEV
	memset (&dev, 0, sizeof (dev));

	strcpy (dev.name, "nulldev");
	dev.flags = DEV_FLAGS_OUTPUT | DEV_FLAGS_INPUT | DEV_FLAGS_SYSTEM;
	dev.putc = nulldev_putc;
	dev.puts = nulldev_puts;
	dev.getc = nulldev_input;
	dev.tstc = nulldev_input;

	device_register (&dev);
#endif
}

二、设备注册

有连个设备注册函数，一个的参数时devces结构体，另一个的参数是设备的名称

2.1device_register (device_t * dev)

设备注册，将结构体添加到devlist的后面，device_register函数的源码如下：

int device_register (device_t * dev)
{
	ListInsertItem (devlist, dev, LIST_END);
	return 0;
}

/*******************************/

/*
 * returns 1 if the item is inserted, returns 0 if out of memory or
 * bad arguments were passed.
 */
int ListInsertItem (list_t list, void *ptrToItem, int itemPosition)
{
	return ListInsertItems (list, ptrToItem, itemPosition, 1);
}

/*******************************/

int ListInsertItems (list_t list, void *ptrToItems, int firstItemPosition,
		     int numItemsToInsert)
{
	int numItems = (*list)->numItems;

	if (firstItemPosition == numItems + 1)
		firstItemPosition = LIST_END;
	else if (firstItemPosition > numItems)
		return 0;

	if ((*list)->numItems >= (*list)->listSize) {
		if (!ExpandListSpace (list, -numItemsToInsert))
			return 0;
	}

	if (firstItemPosition == LIST_START) {
		if (numItems == 0) {
			/* special case for empty list */
			firstItemPosition = LIST_END;
		} else {
			firstItemPosition = 1;
		}
	}

	if (firstItemPosition == LIST_END) {	/* add at the end of the list */
		if (ptrToItems)
			memcpy (ITEMPTR (list, numItems), ptrToItems,
					(*list)->itemSize * numItemsToInsert);
		else
			memset (ITEMPTR (list, numItems), 0,
					(*list)->itemSize * numItemsToInsert);

		(*list)->numItems += numItemsToInsert;
	} else {					/* move part of list up to make room for new item */
		memmove (ITEMPTR (list, firstItemPosition - 1 + numItemsToInsert),
			 ITEMPTR (list, firstItemPosition - 1),
			 (numItems + 1 - firstItemPosition) * (*list)->itemSize);

		if (ptrToItems)
			memmove (ITEMPTR (list, firstItemPosition - 1), ptrToItems,
					 (*list)->itemSize * numItemsToInsert);
		else
			memset (ITEMPTR (list, firstItemPosition - 1), 0,
					(*list)->itemSize * numItemsToInsert);

		(*list)->numItems += numItemsToInsert;
	}

	return 1;
}

2.2device_deregister(char *devname)

int device_deregister(char *devname)
{
	int i,l,dev_index;
	device_t *dev = NULL;
	char temp_names[3][8];

	dev_index=-1;
	for (i=1; i<=ListNumItems(devlist); i++) {
		dev = ListGetPtrToItem (devlist, i);
		if(strcmp(dev->name,devname)==0) {
			dev_index=i;
			break;
		}
	}
	if(dev_index<0) /* device not found */
		return 0;
	/* get stdio devices (ListRemoveItem changes the dev list) */
	for (l=0 ; l< MAX_FILES; l++) {
		if (stdio_devices[l] == dev) {
			/* Device is assigned -> report error */
			return -1;
		}
		memcpy (&temp_names[l][0],
			stdio_devices[l]->name,
			sizeof(stdio_devices[l]->name));
	}
	ListRemoveItem(devlist,NULL,dev_index);
	/* reassign Device list */
	for (i=1; i<=ListNumItems(devlist); i++) {
		dev = ListGetPtrToItem (devlist, i);
		for (l=0 ; l< MAX_FILES; l++) {
			if(strcmp(dev->name,temp_names[l])==0) {
				stdio_devices[l] = dev;
			}
		}
	}
	return 0;
}

三、设备搜索

/* search a device */
device_t *search_device (int flags, char *name)
{
	int i, items;
	device_t *dev = NULL;

	items = ListNumItems (devlist);
	if (name == NULL)
		return dev;

	for (i = 1; i <= items; i++) {
		dev = ListGetPtrToItem (devlist, i);
		if ((dev->flags & flags) && (strcmp (name, dev->name) == 0)) {
			break;
		}
	}
	return dev;
}