Ti437x LED总线驱动模型程序+设备树
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本文主要记录AM437X驱动的LED。含简单的字符设备驱动、设备驱动模型、设备树以及LED子系统。
目前就Linux驱动的理解是:
Linux驱动 = 裸机 + 框架
关于框架,目前的理解是:
以LED驱动为例,之前印象中就是韦老大的思路,现在init里注册、硬件初始化,然后应用层open()、read()就调用了file_operations里面的drv_open()、drv_write()等,算是最简单的驱动框架。
然后韦老大又提及了总线设备驱动模型,将设备和驱动分离,感受到了新的框架。不久前,简单接触了下设备树,感觉就是总线设备驱动模型的修改(升级),将原来的设备部分,不再单独放在代码里,而是放在dts里面,开机加载,然后驱动匹配获取硬件资源。因此,感觉驱动的框架在一步一步的发展,优化,最原始的注册、open等框架,还是不变。
同时,了解到了除输入子系统的其它子系统,加深了对这一模式的理解。感觉就是,将某个硬件资源无缝的融入现有的环境中,而无须改变应用层的程序。
这就是目前的一点小小理解吧,算是打开了个入口,希望以后了解得更加全面、细致。
1.搭建开发环境
1.1安装TI_SDK
先在TI官网下载ti-processor-sdk-linux-am437x-evm-01.00.00.03-Linux-x86-Install.bin
在Ubuntu(only Ubuntu 12.04 LTS and Ubuntu 14.04 LTS are supported)下,对该文件加入可执行权限,然后直接运行。安装目录选择默认即可。完成之后,便在当前用户的home目录生成了所有所需文件。
1.2编译内核
在当前生成ti-processor-sdk-linux-am437x-evm-01.00.00.03目录下,有个Makefile,打开后可以看到相关的编译选项,如:
- 编译全部文件:
make all
- 编译内核:
make linux
- 编译u-boot:
make u-boot-spl
- 以及make的依赖:
-include Rules.make
。在本层目录里,打开Rules.make
,可以知道内核的默认配置文件:
#defconfigDEFCONFIG=tisdk_am437x-evm_defconfig
通过查找,tisdk_am437x-evm_defconfig在~/ti-processor-sdk-linux-am437x-evm-01.00.00.03/board-support/linux-3.14.43+gitAUTOINC+875c69b2c3-g875c69b/arch/arm/configs
里。
这里通过修改该配置文件,然后重新编译内核,即可关闭系统LED相关的驱动,在后面自己写LED驱动时,防止互相干扰。
因此将tisdk_am437x-evm_defconfig配置文件里的所有有关LED的配置都关闭掉。
最后在顶层目录执行make linux
,编译完成后,生成~/ti-processor-sdk-linux-am437x-evm-01.00.00.03/board-support/linux-3.14.43+gitAUTOINC+875c69b2c3-g875c69b/arch/arm/boot/zImage
文件。
1.3烧写SD卡
回到~/ti-processor-sdk-linux-am437x-evm-01.00.00.03/bin
下,TI制作了很多脚本,其中的create-sdcard.sh
就是制作SD卡的。Ubuntu插上SD卡,然后切换成root用户,执行该脚本,根据提示一路选择下去即可。
这里烧写完了,测试发现并没有使用之前编译的内核,分析脚本后发现,该脚本直接使用的~/ti-processor-sdk-linux-am437x-evm-01.00.00.03/filesystem
下的tisdk-rootfs-image-am437x-evm.tar.gz
。脚本将该文件作为根文件系统放入SD卡,因此并没有使用之前编译的内核。解决方法要么在执行脚本的过程中根据提示输入相关的路径,要么在制作好SD卡后,将编译好的内核覆盖掉SD卡的内核即可。我选择的后者:cp ~/ti-processor-sdk-linux-am437x-evm-01.00.00.03/board-support/linux-3.14.43+gitAUTOINC+875c69b2c3-g875c69b/arch/arm/boot/zImage /media/hceng/rootfs/boot/
。
最后将制作好的SD卡插上开发板启动即可。
2.简单的字符驱动
先记录下几个重要类型或结构体:
- 表示设备号(32位机中:高12位表示主设备号,低20位表示次设备号)
typedef __kernel_dev_t dev_t;
- 描述字符设备
struct cdev { struct kobject kobj; //内嵌kobject结构体,用于设备驱动模型管理 struct module *owner; //包含指向该结构的模块的指针,用于引用计数 const struct file_operations *ops; //指向字符设备操作函数集的指针 struct list_head list; //该结构将使用该驱动的字符设备连接成一个链表 dev_t dev; //该字符设备的其实设备号,一个设备可能有多个设备号 unsigned int count; //使用该字符设备驱动的设备数量};
- 描述类
struct class{ const char *name; //类名称 struct module *owner; //对应模块 struct subsystem subsys; //对应的subsystem; struct list_head children; //class_device链表 struct list_head interfaces; //class_interface链表 struct semaphore sem; /用于同步的信号锁 struct class_attribute *class_attrs; //类属性 int (*uevent)(struct class_device *dev,char **envp,int num_envp, char *buffer,int buffer_size); //事件 void (*release)(struct class_device *dev); //释放类设备 void (*class_release)(struct class *class); //释放类}
总结下,目前理解的字符设备编写流程:
1)驱动加载函数:
xx_drv_init()
1.1)申请设备号:alloc_chrdev_region()
1.2)cde初始化(绑定fops):cdev_init()
1.3)注册到内核:cdev_add()
1.4)创建类:class_create()
1.5)向类中添加设备(mdev自动创建设备节点):device_create()
1.6)硬件相关(内存映射):ioremap()
2)驱动卸载函数:xx_drv_exit()
2.1)移除设备:device_destroy()
2.2)移除类:class_destroy()
2.3)注销cdev:cdev_del()
2.4)释放设备号:unregister_chrdev()
2.5)释放内存:iounmap()
3)必要修饰:module_init(xx_drv_init);module_exit(xx_drv_exit);MODULE_LICENSE("GPL");
4)构造file_operations:struct file_operations xx_drv_fops;
5)实现file_operations里每个函数:xx_open()、xx_write()……
2.1驱动代码
{[leds_drv.c] https://github.com/hceng/am437x/blob/master/drive/1th_led/v1.0/leds_drv.c %}
#include <linux/kernel.h>#include <linux/module.h>#include <linux/fs.h>#include <linux/init.h>#include <asm/uaccess.h>#include <asm/io.h>#include <linux/device.h>#include <linux/cdev.h>#define TI_LEDS_CNT 4int major;static struct cdev leds_cdev;static struct class *leds_cls;static volatile unsigned long *PRCM_CM_PER_GPIO5_CLKCTRL = NULL; static volatile unsigned long *CTRL_CONF_UART3_RXD = NULL; static volatile unsigned long *CTRL_CONF_UART3_TXD = NULL; static volatile unsigned long *CTRL_CONF_UART3_CTSN = NULL;static volatile unsigned long *CTRL_CONF_UART3_RTSN = NULL;static volatile unsigned long *GPIO_OE = NULL;static volatile unsigned long *GPIO_SETDATAOUT = NULL;static volatile unsigned long *GPIO_DATAOUT = NULL; static int leds_drv_open(struct inode *inode, struct file *file) { int minor = iminor(file->f_inode); printk(KERN_INFO"%s OK.\n",__func__); *PRCM_CM_PER_GPIO5_CLKCTRL = (0x01<<1); *CTRL_CONF_UART3_RXD &= ~(0x7<<0 | 0x01<<16 | 0x01<<17 | 0x01<<18); *CTRL_CONF_UART3_RXD |= (0x7<<0 | 0x01<<17); *GPIO_OE &= ~(0x01<<minor); *GPIO_SETDATAOUT |= (0x01<<minor); return 0; } static ssize_t leds_drv_write(struct file *file, const char __user *user_buf, size_t count, loff_t * ppos) { int minor = iminor(file->f_inode); char buf; printk(KERN_INFO"%s OK.\n",__func__); if(count != 1){ printk(KERN_INFO"write count != 1.\n"); return 1; } if (copy_from_user(&buf, user_buf, count)) return -EFAULT; if (0x01 == buf) *GPIO_DATAOUT |= (0x01<<minor); else if(0x00 == buf) *GPIO_DATAOUT &= ~(0x01<<minor); return 0; } static struct file_operations leds_fops = { .owner = THIS_MODULE, .open = leds_drv_open, .write = leds_drv_write, };static int leds_drv_init(void){ //1.申请设备号 dev_t devid; printk(KERN_INFO"%s OK.\n",__func__); if(alloc_chrdev_region(&devid, 0, TI_LEDS_CNT, "ti_leds") < 0) { printk(KERN_INFO"%s ERROR.\n",__func__); goto error; } major = MAJOR(devid); //2.注册到系统中 cdev_init(&leds_cdev, &leds_fops); cdev_add(&leds_cdev, devid, TI_LEDS_CNT); leds_cls = class_create(THIS_MODULE, "ti_leds"); device_create(leds_cls, NULL, MKDEV(major, 0), NULL, "ti_led0"); device_create(leds_cls, NULL, MKDEV(major, 1), NULL, "ti_led1"); device_create(leds_cls, NULL, MKDEV(major, 2), NULL, "ti_led2"); device_create(leds_cls, NULL, MKDEV(major, 3), NULL, "ti_led3"); //3.硬件相关 PRCM_CM_PER_GPIO5_CLKCTRL = ioremap(0x44DF8800+0x498, 0x04*1); CTRL_CONF_UART3_RXD = ioremap(0x44E10000+0xA28, 0x04*4); CTRL_CONF_UART3_TXD = CTRL_CONF_UART3_RXD + 1; CTRL_CONF_UART3_CTSN = CTRL_CONF_UART3_RXD + 2; CTRL_CONF_UART3_RTSN = CTRL_CONF_UART3_RXD + 3; GPIO_OE = ioremap(0x48322000+0x134, 0x04); GPIO_DATAOUT = ioremap(0x48322000+0x13C, 0x04); GPIO_SETDATAOUT = ioremap(0x48322000+0x194, 0x04);error: unregister_chrdev_region(MKDEV(major, 0), TI_LEDS_CNT); return 0;}static void leds_drv_exit(void){ unsigned i; printk(KERN_INFO"%s OK.\n",__func__); for(i=0;i<TI_LEDS_CNT;i++) { device_destroy(leds_cls, MKDEV(major, i)); } class_destroy(leds_cls); cdev_del(&leds_cdev); unregister_chrdev(major, "ti_leds"); iounmap(PRCM_CM_PER_GPIO5_CLKCTRL); iounmap(CTRL_CONF_UART3_RXD); iounmap(GPIO_OE); iounmap(GPIO_DATAOUT); iounmap(GPIO_SETDATAOUT);}module_init(leds_drv_init);module_exit(leds_drv_exit);MODULE_LICENSE("GPL");MODULE_AUTHOR("hceng <huangcheng.job@foxmail.com>");MODULE_DESCRIPTION("TI am437x board leds drvice");MODULE_ALIAS("character device:ti_leds");MODULE_VERSION("V1.0");
2.2测试代码(跑马灯)
{[leds_app.c] https://github.com/hceng/am437x/blob/master/drive/1th_led/v1.0/leds_app.c }
#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <stdio.h>#include <unistd.h>#define msleep(x) usleep(x*1000)int main(int argc, char **argv){ int fd[4]; int val = 0; int i = 0; //const char *dev[] = {"/dev/ti_led0", "/dev/ti_led1", "/dev/ti_led2", "/dev/ti_led3"}; const char *dev[] = {"/dev/ti_led2", "/dev/ti_led0", "/dev/ti_led3", "/dev/ti_led1"}; for(i=0; i<4; i++) { fd[i] = open(dev[i], O_RDWR); if (fd[i] < 0) { printf("can't open %s\n", *dev[i]); return 0; } } //leds off all. for(i=0; i<4; i++) { write(fd[i], &val, 1); } //flicker leds. while(1) { val = !val; for(i=0; i<4; i++) { write(fd[i], &val, 1); msleep(300); } }}
2.3关于printk调试
内核的printk定义了如下的打印等级:
#define KERN_EMERG "<0>" /* system is unusable */#define KERN_ALERT "<1>" /* action must be taken immediately */#define KERN_CRIT "<2>" /* critical conditions */#define KERN_ERR "<3>" /* error conditions */#define KERN_WARNING "<4>" /* warning conditions */#define KERN_NOTICE "<5>" /* normal but significant condition */#define KERN_INFO "<6>" /* informational */#define KERN_DEBUG "<7>" /* debug-level messages */
- 如果使用串口登陆,可通过修改/proc/sys/kernel/printk里的参数进行设置:
echo "8 4 1 7" >/proc/sys/kernel/printk
上面的四个数字分别代表:
控制台日志级别:优先级[s1] 高于该值的消息将被打印至控制台,[s1]数值越小,优先级越高;
默认的消息日志级别:将用该优先级来打印没有优先级的消息;
最低的控制台日志级别:控制台日志级别可被设置的最小值(最高优先级);
默认的控制台日志级别:控制台日志级别的缺省值;
- 如果使用SSH登陆,是无法显示printk的打印信息的,但打印的数据会被放在
/var/log/messages
和/proc/kmsg
中,利用这一特性,可以后台运行tail命令进行侦测:
tail -f /var/log/messages &
缺点是不能设置打印等级,同时内核的其它信息也会被打印出来。
3.设备驱动模型驱动
关于设备驱动模型前面以及有点了解,在写驱动的时候,主要体现在将原本的硬件资源信息抽取了出来,单独放在了一个文件里,当两个文件的分别加载的时候,根据名字匹配,匹配成功则调用probe()函数,进行类似前面的init()进行初始化。其它的内容基本一样,该干嘛就干嘛。
3.1驱动代码
{ [leds_dev.c] https://github.com/hceng/am437x/blob/master/drive/1th_led/v2.0/leds_dev.c }
#include <linux/init.h>#include <linux/module.h>#include <linux/kernel.h>#include <linux/fs.h>#include <linux/delay.h>#include <asm/uaccess.h>#include <asm/irq.h>#include <asm/io.h>#include <linux/device.h>#include <linux/platform_device.h>/************************************************** TI_BOARD --------------------------------------------------- Ball Color Mode Pin --------------------------------------------------- H24 D7_Blue 0x07 uart3_txd(GPIO5_3) H25 D8_Blue 0x07 uart3_rxd(GPIO5_2) K24 D9_Green 0x07 uart3_rtsn(GPIO5_1) H22 D10_Red 0x07 uart3_ctsn(GPIO5_0) **************************************************/static struct resource leds_resource[] = { //PRCM_CM_PER_GPIO5_CLKCTRL(498h) [0] = { .start = 0x44DF8800, .end = 0x44DFFFFF, .name = "CM_PER", .flags = IORESOURCE_MEM, }, //CTRL_CONF_UART3_RXD(A28h)、CTRL_CONF_UART3_TXD(A2Ch)、CTRL_CONF_UART3_CTSN(A30h)、CTRL_CONF_UART3_RTSN((A34h)) [1] = { .start = 0x44E10000, .end = 0x44E1FFFF, .name = "CONTROL_MODULE", .flags = IORESOURCE_MEM, }, //GPIO_OE(134h)、GPIO_SETDATAOUT(194h)、GPIO_DATAOUT(13Ch) [2] = { .start = 0x48322000, .end = 0x48322FFF, .name = "GOIP5", .flags = IORESOURCE_MEM, }, [3] = { .start = 0, .end = 3, .name = "GOIP5_PIN", .flags = IORESOURCE_IO, }}; static void leds_release(struct device * dev) { printk(KERN_INFO"%s OK.\n",__func__);}static struct platform_device leds_dev = { .name = "ti_am437x_leds_platform", .id = -1, .num_resources = ARRAY_SIZE(leds_resource), .resource = leds_resource, .dev = { .release = leds_release, }, };static int leds_dev_init(void) { printk(KERN_INFO"%s OK.\n",__func__); return platform_device_register(&leds_dev);; } static void leds_dev_exit(void) { printk(KERN_INFO"%s OK.\n",__func__); platform_device_unregister(&leds_dev); } module_init(leds_dev_init);module_exit(leds_dev_exit);MODULE_LICENSE("GPL");MODULE_AUTHOR("hceng <huangcheng.job@foxmail.com>");MODULE_DESCRIPTION("TI am437x board leds drvice");MODULE_ALIAS("platform:ti_leds");MODULE_VERSION("V2.0");
{[leds_drv.c] https://github.com/hceng/am437x/blob/master/drive/1th_led/v2.0/leds_drv.c }
#include <linux/module.h> #include <linux/version.h> #include <linux/init.h> #include <linux/fs.h> #include <linux/interrupt.h> #include <linux/irq.h> #include <linux/sched.h> #include <linux/pm.h> #include <linux/sysctl.h> #include <linux/proc_fs.h> #include <linux/delay.h> #include <linux/platform_device.h> #include <linux/input.h> #include <linux/irq.h> #include <asm/uaccess.h> #include <asm/io.h> #include <linux/cdev.h>#include <asm/uaccess.h>#define TI_LEDS_CNT 4int major;static struct cdev leds_cdev;static struct class *leds_cls;static volatile unsigned long *PRCM_CM_PER_GPIO5_CLKCTRL = NULL; static volatile unsigned long *CTRL_CONF_UART3_RXD = NULL; static volatile unsigned long *CTRL_CONF_UART3_TXD = NULL; static volatile unsigned long *CTRL_CONF_UART3_CTSN = NULL;static volatile unsigned long *CTRL_CONF_UART3_RTSN = NULL;static volatile unsigned long *GPIO_OE = NULL;static volatile unsigned long *GPIO_SETDATAOUT = NULL;static volatile unsigned long *GPIO_DATAOUT = NULL; static int leds_drv_open(struct inode *inode, struct file *file) { int minor = iminor(file->f_inode); printk(KERN_INFO"%s OK.\n",__func__); *PRCM_CM_PER_GPIO5_CLKCTRL = (0x01<<1); *CTRL_CONF_UART3_RXD &= ~(0x7<<0 | 0x01<<16 | 0x01<<17 | 0x01<<18); *CTRL_CONF_UART3_RXD |= (0x7<<0 | 0x01<<17); *GPIO_OE &= ~(0x01<<minor); *GPIO_SETDATAOUT |= (0x01<<minor); return 0; } static ssize_t leds_drv_write(struct file *file, const char __user *user_buf, size_t count, loff_t * ppos) { int minor = iminor(file->f_inode); char buf; printk(KERN_INFO"%s OK.\n",__func__); if(count != 1){ printk(KERN_INFO"write count != 1.\n"); return 1; } if (copy_from_user(&buf, user_buf, count)) return -EFAULT; if (0x01 == buf) *GPIO_DATAOUT |= (0x01<<minor); else if(0x00 == buf) *GPIO_DATAOUT &= ~(0x01<<minor); return 0; } static struct file_operations leds_fops = { .owner = THIS_MODULE, .open = leds_drv_open, .write = leds_drv_write, }; static int leds_probe(struct platform_device *pdev) { struct resource *res; dev_t devid; printk(KERN_INFO"%s OK.\n",__func__); //1.申请设备号 if(alloc_chrdev_region(&devid, 0, TI_LEDS_CNT, "ti_leds") < 0) { printk("%s ERROR\n",__func__); goto error; } major = MAJOR(devid); //2.注册到系统中 cdev_init(&leds_cdev, &leds_fops); cdev_add(&leds_cdev, devid, TI_LEDS_CNT); leds_cls = class_create(THIS_MODULE, "ti_leds"); device_create(leds_cls, NULL, MKDEV(major, 0), NULL, "ti_led0"); device_create(leds_cls, NULL, MKDEV(major, 1), NULL, "ti_led1"); device_create(leds_cls, NULL, MKDEV(major, 2), NULL, "ti_led2"); device_create(leds_cls, NULL, MKDEV(major, 3), NULL, "ti_led3"); //3.硬件相关 res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "CM_PER"); if (!res) return -EINVAL; PRCM_CM_PER_GPIO5_CLKCTRL = ioremap(res->start+0x498, 0x04*1); res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "CONTROL_MODULE"); if (!res) return -EINVAL; CTRL_CONF_UART3_RXD = ioremap(res->start+0xA28, 0x04*4); CTRL_CONF_UART3_TXD = CTRL_CONF_UART3_RXD + 1; CTRL_CONF_UART3_CTSN = CTRL_CONF_UART3_RXD + 2; CTRL_CONF_UART3_RTSN = CTRL_CONF_UART3_RXD + 3; res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "GOIP5"); if (!res) return -EINVAL; GPIO_OE = ioremap(res->start+0x134, 0x04); GPIO_DATAOUT = ioremap(res->start+0x13C, 0x04); GPIO_SETDATAOUT = ioremap(res->start+0x194, 0x04); *PRCM_CM_PER_GPIO5_CLKCTRL = (0x01<<1);//使能GPIO外设时钟error: unregister_chrdev_region(MKDEV(major, 0), TI_LEDS_CNT); return 0; } static int leds_remove(struct platform_device *pdev) { unsigned i; printk(KERN_INFO"%s OK.\n",__func__); for(i=0;i<TI_LEDS_CNT;i++) { device_destroy(leds_cls, MKDEV(major, i)); } class_destroy(leds_cls); cdev_del(&leds_cdev); unregister_chrdev(major, "ti_leds"); iounmap(PRCM_CM_PER_GPIO5_CLKCTRL); iounmap(CTRL_CONF_UART3_RXD); iounmap(GPIO_OE); iounmap(GPIO_DATAOUT); iounmap(GPIO_SETDATAOUT); return 0; }struct platform_driver leds_drv = { .probe = leds_probe, .remove = leds_remove, .driver = { .name = "ti_am437x_leds_platform", } }; static int leds_drv_init(void) { printk(KERN_INFO"%s OK.\n",__func__); return platform_driver_register(&leds_drv); } static void leds_drv_exit(void) { printk(KERN_INFO"%s OK.\n",__func__); platform_driver_unregister(&leds_drv); } module_init(leds_drv_init);module_exit(leds_drv_exit);MODULE_LICENSE("GPL");MODULE_AUTHOR("hceng <huangcheng.job@foxmail.com>");MODULE_DESCRIPTION("TI am437x board leds drvice");MODULE_ALIAS("platform:ti_leds");MODULE_VERSION("V2.0");
测试程序同前面的一样。
4.设备树驱动
4.1初识设备树
1)前面的总线设备驱动模型中,硬件资源来自于leds_dev.c里面的信息,这样会导致不同的板子,会添加不同的硬件资源信息,造成内核的臃肿。
2)使用设备树后,内核不再包含硬件的描述,硬件描述放在单独的DTS里面,然后编译成二进制的DTB,在U-Boot启动的时候加载进去,然后内核进行解析。
3)DTS、DTC和DTB之间的关系:
DTS经过DTC编译得到DTB,DTB通过DTC反编译得到DTS.
4)ARM中,所有的DTS文件放在
arch/arm/boot/dts
目录中,为了简化,将Soc公用部分提取了出来作为dtsi,类似头文件。
5)DTC编译工具的源代码在scripts/dtc目录中,编译内核时,编译内核时,需要使能才能将源码编译成工具,对应于scripts/dtc/Makefile
中"hostprogs-y:=dtc"
。Ubuntu也可直接安装DTC工具:
sudo apt-get install device-tree-compiler
6)内核的
arch/arm/boot/dts/Makefile
中,描述了当某种Soc被选中后,哪些.dtb会编译出来。执行make dtbs
,会根据arch/arm/Makefile
编译指定目标。
7)单独编译与反编译:
./scripts/dtc/dtc -I dts -O dtb -o xxx.dtb arch/arm/boot/dts/xxx.dts //dts->dtb./scripts/dtc/dtc -I dtb -O dts -o xxx.dts arch/arm/boot/dts/xxx.dtb //dtb->dts
8)后面认识深刻了,再总结总结。
4.2修改AM437x设备树
AM437x的设备树文件在~/ti-processor-sdk-linux-am437x-evm-01.00.00.03/board-support/linux-3.14.43+gitAUTOINC+875c69b2c3-g875c69b/arch/arm/boot/dts/
中,主要是am4372.dtsi和am437x-sk-evm.dts。
- 我的目的是希望写个设备树框架的LED程序,因此想让am437x-sk-evm.dts干净点,只包含LED硬件描述,因此我需要删除am437x-sk-evm.dts里面的其它硬件描述。经过测试,am437x-sk-evm.dts里面包含部分MMC的描述,一旦删除将不能成功启动内核。而且,后面调试的时候,希望开发板通过NFS挂载的方式,直接加载编译的驱动模块,因此需要保留网卡描述部分。最后,将MMC和网卡必须的部分,提取了出来,放在了am4372.dtsi中。精简后的am437x-sk-evm.dts内容如下:
{[am437x-sk-evm.dts] https://github.com/hceng/am437x/blob/master/drive/1th_led/v3.0/am437x-sk-evm.dts }
/* AM437x SK EVM *//dts-v1/;#include "am4372.dtsi"#include <dt-bindings/pinctrl/am43xx.h>#include <dt-bindings/gpio/gpio.h>/ { model = "TI AM437x SK EVM"; compatible = "ti,am437x-sk-evm","ti,am4372","ti,am43"; led_pin { compatible = "ti_leds"; pinctrl-names = "default"; pinctrl-0 = <&leds_pins>; am437x,led_gpio0 = <&gpio5 0 GPIO_ACTIVE_HIGH>; am437x,led_gpio1 = <&gpio5 1 GPIO_ACTIVE_HIGH>; am437x,led_gpio2 = <&gpio5 2 GPIO_ACTIVE_HIGH>; am437x,led_gpio3 = <&gpio5 3 GPIO_ACTIVE_HIGH>; };};&am43xx_pinmux { leds_pins: leds_pins { pinctrl-single,pins = < 0x228 (PIN_OUTPUT | MUX_MODE7) /* uart3_rxd.gpio5_2 */ 0x22c (PIN_OUTPUT | MUX_MODE7) /* uart3_txd.gpio5_3 */ 0x230 (PIN_OUTPUT | MUX_MODE7) /* uart3_ctsn.gpio5_0 */ 0x234 (PIN_OUTPUT | MUX_MODE7) /* uart3_rtsn.gpio5_1 */ >; };};&gpio5 { status = "okay";};
额,在调试的过程中,需要不断编译新的DTB和复制到SD卡的rootfs分区中,仿照前面写了个脚本进行自动编译和复制,同时检查文件的生成时间间隔,实际中,确实减少了焦躁的重复操作。
4.3驱动代码
{[leds_drv.c] https://github.com/hceng/am437x/blob/master/drive/1th_led/v3.0/leds_drv.c}
#include <linux/module.h> #include <linux/version.h> #include <linux/init.h> #include <linux/fs.h> #include <linux/interrupt.h> #include <linux/irq.h> #include <linux/sched.h> #include <linux/pm.h> #include <linux/sysctl.h> #include <linux/proc_fs.h> #include <linux/delay.h> #include <linux/platform_device.h> #include <linux/input.h> #include <linux/irq.h> #include <asm/uaccess.h> #include <asm/io.h> #include <linux/cdev.h>#include <asm/uaccess.h>#include <linux/gpio.h>#include <linux/of_gpio.h>#define TI_LEDS_CNT 4int major;static struct cdev leds_cdev;static struct class *leds_cls;static int led0,led1,led2,led3; static int leds_drv_open(struct inode *inode, struct file *file) { printk(KERN_INFO"%s OK.\n",__func__); return 0; } static ssize_t leds_drv_write(struct file *file, const char __user *user_buf, size_t count, loff_t * ppos) { int minor = iminor(file->f_inode); char buf; printk(KERN_INFO"%s OK.\n",__func__); if(count != 1){ printk(KERN_INFO"write count != 1.\n"); return 1; } if (copy_from_user(&buf, user_buf, count)) return -EFAULT; if(0x01 == buf) { switch(minor){ case 0: gpio_set_value(led0, 0); break; case 1: gpio_set_value(led1, 0); break; case 2: gpio_set_value(led2, 0); break; case 3: gpio_set_value(led3, 0); break; default: printk(KERN_INFO"%s receive minor error.\n",__func__); } } else if(0x00 == buf) { switch(minor){ case 0: gpio_set_value(led0, 1); break; case 1: gpio_set_value(led1, 1); break; case 2: gpio_set_value(led2, 1); break; case 3: gpio_set_value(led3, 1); break; default: printk(KERN_INFO"%s receive minor error\n",__func__); } } return 0; } static struct file_operations leds_fops = { .owner = THIS_MODULE, .open = leds_drv_open, .write = leds_drv_write, }; static int leds_probe(struct platform_device *pdev) { struct device *dev = &pdev->dev; dev_t devid; printk(KERN_INFO"%s OK.\n",__func__); //1.申请设备号 if(alloc_chrdev_region(&devid, 0, TI_LEDS_CNT, "ti_leds") < 0) { printk(KERN_INFO"%s ERROR.\n",__func__); goto error; } major = MAJOR(devid); //2.注册到系统中 cdev_init(&leds_cdev, &leds_fops); cdev_add(&leds_cdev, devid, TI_LEDS_CNT); leds_cls = class_create(THIS_MODULE, "ti_leds"); device_create(leds_cls, NULL, MKDEV(major, 0), NULL, "ti_led0"); device_create(leds_cls, NULL, MKDEV(major, 1), NULL, "ti_led1"); device_create(leds_cls, NULL, MKDEV(major, 2), NULL, "ti_led2"); device_create(leds_cls, NULL, MKDEV(major, 3), NULL, "ti_led3"); //3.硬件相关 led0 = of_get_named_gpio(dev->of_node, "am437x,led_gpio0", 0);; led1 = of_get_named_gpio(dev->of_node, "am437x,led_gpio1", 0);; led2 = of_get_named_gpio(dev->of_node, "am437x,led_gpio2", 0);; led3 = of_get_named_gpio(dev->of_node, "am437x,led_gpio3", 0); //printk(KERN_INFO"led0 = %d\n",led0); //printk(KERN_INFO"led1 = %d\n",led1); //printk(KERN_INFO"led2 = %d\n",led2); //printk(KERN_INFO"led3 = %d\n",led3); devm_gpio_request_one(dev, led0, GPIOF_OUT_INIT_HIGH, "LED0"); devm_gpio_request_one(dev, led1, GPIOF_OUT_INIT_HIGH, "LED1"); devm_gpio_request_one(dev, led2, GPIOF_OUT_INIT_HIGH, "LED2"); devm_gpio_request_one(dev, led3, GPIOF_OUT_INIT_HIGH, "LED3");error: unregister_chrdev_region(MKDEV(major, 0), TI_LEDS_CNT); return 0; } static int leds_remove(struct platform_device *pdev) { unsigned i; printk(KERN_INFO"%s OK.\n",__func__); for(i=0;i<TI_LEDS_CNT;i++) { device_destroy(leds_cls, MKDEV(major, i)); } class_destroy(leds_cls); cdev_del(&leds_cdev); unregister_chrdev(major, "ti_leds"); return 0; }static const struct of_device_id of_gpio_leds_match[] = { { .compatible = "ti_leds", }, {},};static struct platform_driver leds_drv = { .probe = leds_probe, .remove = leds_remove, .driver = { .name = "ti_am437x_leds_platform", .owner = THIS_MODULE, .of_match_table = of_match_ptr(of_gpio_leds_match), },};static int leds_drv_init(void) { printk(KERN_INFO"%s OK.\n",__func__); return platform_driver_register(&leds_drv); } static void leds_drv_exit(void) { printk(KERN_INFO"%s OK.\n",__func__); platform_driver_unregister(&leds_drv); } module_init(leds_drv_init);module_exit(leds_drv_exit);MODULE_LICENSE("GPL");MODULE_AUTHOR("hceng <huangcheng.job@foxmail.com>");MODULE_DESCRIPTION("TI am437x board leds drvice");MODULE_ALIAS("platform:device tree:ti_leds");MODULE_VERSION("V3.0");
测试程序同前面的一样。
6.心得
在我理解到驱动=裸机+软件框架的时候,我对之前的裸机也就没那么排斥了。
而且这个软件框架,就现在来看,核心的那几步像:申请设备号、注册设备、创建类和创建节点这些都不变
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