S3C2440驱动简析——触摸屏驱动
因困于杂事，博客荒废将近半个月，此时此刻重提笔墨，继续记录鄙人学习之历程。
本文将简要分析2440的触摸屏驱动，其驱动程序内核自带。在浏览本文之前，如果对Linux 驱动的input 子系统没有认识的话，请先回头参考鄙人之前的博文《input子系统》http://blog.csdn.net/jarvis_xian/article/details/6552579
事不宜迟，马上进入本文的正题。有经验的朋友都知道，看驱动，先找入口、出口！
static int __init s3c2410ts_init(void)
{
return platform_driver_register(&s3c_ts_driver);//注册platform驱动，注意参数s3c_ts_driver
}
static void __exit s3c2410ts_exit(void)
{
platform_driver_unregister(&s3c_ts_driver); //注销platform驱动
}
platform_driver_register 的参数s3c_ts_driver 定义如下
static struct platform_driver s3c_ts_driver = {
.driver = {
.name = "samsung-ts",
.owner = THIS_MODULE,
#ifdef CONFIG_PM
.pm = &s3c_ts_pmops,
#endif
},
.id_table = s3cts_driver_ids,
.probe = s3c2410ts_probe,
.remove = __devexit_p(s3c2410ts_remove),
};
在上述结构体中，我们应该把精力放在.probe、.remove和.pm上
探讨probe 函数前，我们先看一下结构体ts 的定义，其统筹了整个驱动所用到的资源
struct s3c2410ts {
struct s3c_adc_client *client;
struct device *dev;
struct input_dev *input;
struct clk *clock;
void __iomem *io;
unsigned long xp;
unsigned long yp;
int irq_tc;
int count;
int shift;
int features;
};
s3c2410ts_probe代码如下：
static int __devinit s3c2410ts_probe(struct platform_device *pdev)
{
struct s3c2410_ts_mach_info *info;
struct device *dev = &pdev->dev;
struct input_dev *input_dev;
struct resource *res;
int ret = -EINVAL;
/* Initialise input stuff */
memset(&ts, 0, sizeof(struct s3c2410ts));
ts.dev = dev; //把platform的设备挂到ts 结构体
info = pdev->dev.platform_data;
if (!info) {
dev_err(dev, "no platform data, cannot attach\n");
return -EINVAL;
}
dev_dbg(dev, "initialising touchscreen\n");
ts.clock = clk_get(dev, "adc"); //得到adc 时钟资源
if (IS_ERR(ts.clock)) {
dev_err(dev, "cannot get adc clock source\n");
return -ENOENT;
}
clk_enable(ts.clock); //使能ts 时钟
dev_dbg(dev, "got and enabled clocks\n");
ts.irq_tc = ret = platform_get_irq(pdev, 0); //获取中断资源
if (ret < 0) {
dev_err(dev, "no resource for interrupt\n");
goto err_clk;
}
res = platform_get_resource(pdev, IORESOURCE_MEM, 0); //获取占用端口的大小
if (!res) {
dev_err(dev, "no resource for registers\n");
ret = -ENOENT;
goto err_clk;
}
ts.io = ioremap(res->start, resource_size(res)); //物理地址映射到虚拟地址
if (ts.io == NULL) {
dev_err(dev, "cannot map registers\n");
ret = -ENOMEM;
goto err_clk;
}
/* inititalise the gpio */
if (info->cfg_gpio)
info->cfg_gpio(to_platform_device(ts.dev));
ts.client = s3c_adc_register(pdev, s3c24xx_ts_select,
s3c24xx_ts_conversion, 1);
if (IS_ERR(ts.client)) {
dev_err(dev, "failed to register adc client\n");
ret = PTR_ERR(ts.client);
goto err_iomap;
}
/* Initialise registers */
if ((info->delay & 0xffff) > 0)
writel(info->delay & 0xffff, ts.io + S3C2410_ADCDLY); //初始化延时寄存器
writel(WAIT4INT | INT_DOWN, ts.io + S3C2410_ADCTSC);
input_dev = input_allocate_device(); //为input_dev 分配空间并初始化
if (!input_dev) {
dev_err(dev, "Unable to allocate the input device !!\n");
ret = -ENOMEM;
goto err_iomap;
}
ts.input = input_dev; //把input_dev 挂接到ts 结构体
ts.input->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS); //设置事件类型
ts.input->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
input_set_abs_params(ts.input, ABS_X, 0, 0x3FF, 0, 0); //设置边界条件等
input_set_abs_params(ts.input, ABS_Y, 0, 0x3FF, 0, 0);
ts.input->name = "S3C24XX TouchScreen";
ts.input->id.bustype = BUS_HOST;
ts.input->id.vendor = 0xDEAD;
ts.input->id.product = 0xBEEF;
ts.input->id.version = 0x0102;
ts.shift = info->oversampling_shift;
ts.features = platform_get_device_id(pdev)->driver_data;
ret = request_irq(ts.irq_tc, stylus_irq, IRQF_DISABLED,
"s3c2410_ts_pen", ts.input);
if (ret) {
dev_err(dev, "cannot get TC interrupt\n");
goto err_inputdev;
}
dev_info(dev, "driver attached, registering input device\n");
/* All went ok, so register to the input system */
ret = input_register_device(ts.input); //初始化完毕后，注册input 子系统
if (ret < 0) {
dev_err(dev, "failed to register input device\n");
ret = -EIO;
goto err_tcirq;
}
return 0;
err_tcirq:
free_irq(ts.irq_tc, ts.input);
err_inputdev:
input_free_device(ts.input);
err_iomap:
iounmap(ts.io);
err_clk:
del_timer_sync(&touch_timer);
clk_put(ts.clock);
return ret;
}
相对于probe，remove的代码如下static int __devexit s3c2410ts_remove(struct platform_device *pdev) { free_irq(ts.irq_tc, ts.input); //释放中断资源 del_timer_sync(&touch_timer); //卸载软件时钟 clk_disable(ts.clock); //禁能 clk_put(ts.clock); input_unregister_device(ts.input); //注销输入子系统 iounmap(ts.io); //解除地址映射 return 0; }static struct dev_pm_ops s3c_ts_pmops = { .suspend = s3c2410ts_suspend, .resume = s3c2410ts_resume, }; 包含了suspend 和resume 两个操作。static int s3c2410ts_suspend(struct device *dev) { writel(TSC_SLEEP, ts.io + S3C2410_ADCTSC); //把挂起状态写入硬件寄存器 disable_irq(ts.irq_tc); clk_disable(ts.clock); return 0; }static int s3c2410ts_resume(struct device *dev) { struct platform_device *pdev = to_platform_device(dev); struct s3c2410_ts_mach_info *info = pdev->dev.platform_data; clk_enable(ts.clock); enable_irq(ts.irq_tc); /* Initialise registers */ if ((info->delay & 0xffff) > 0) //写入延时初值 writel(info->delay & 0xffff, ts.io + S3C2410_ADCDLY); writel(WAIT4INT | INT_DOWN, ts.io + S3C2410_ADCTSC); //写入工作状态 return 0; }经过上述代码的铺垫，我们已经有了一个舒适的环境，剩下的工作，就在与中断相关的函数里完成了。static irqreturn_t stylus_irq(int irq, void *dev_id) { unsigned long data0; unsigned long data1; bool down; data0 = readl(ts.io + S3C2410_ADCDAT0); //读取X、Y轴坐标 data1 = readl(ts.io + S3C2410_ADCDAT1); down = get_down(data0, data1); //关于get_down函数查看下文 /* TODO we should never get an interrupt with down set while * the timer is running, but maybe we ought to verify that the * timer isn't running anyways. */ if (down) s3c_adc_start(ts.client, 0, 1 << ts.shift); //开始ADC转换 else dev_dbg(ts.dev, "%s: count=%d\n", __func__, ts.count); if (ts.features & FEAT_PEN_IRQ) { //清除标志位（等待下一次中断的到来） /* Clear pen down/up interrupt */ writel(0x0, ts.io + S3C64XX_ADCCLRINTPNDNUP); } return IRQ_HANDLED; }static inline bool get_down(unsigned long data0, unsigned long data1) { //检测触摸屏有没有被按下 /* returns true if both data values show stylus down */ return (!(data0 & S3C2410_ADCDAT0_UPDOWN) && !(data1 & S3C2410_ADCDAT0_UPDOWN)); }touch_timer_fire函数将触摸屏的数据报告给内核static void touch_timer_fire(unsigned long data) { unsigned long data0; unsigned long data1; bool down; data0 = readl(ts.io + S3C2410_ADCDAT0); data1 = readl(ts.io + S3C2410_ADCDAT1); down = get_down(data0, data1); if (down) { if (ts.count == (1 << ts.shift)) { ts.xp >>= ts.shift; ts.yp >>= ts.shift; dev_dbg(ts.dev, "%s: X=%lu, Y=%lu, count=%d\n", __func__, ts.xp, ts.yp, ts.count); input_report_abs(ts.input, ABS_X, ts.xp); //熟悉的操作~~~ input_report_abs(ts.input, ABS_Y, ts.yp); input_report_key(ts.input, BTN_TOUCH, 1); input_sync(ts.input); //结束同步 ts.xp = 0; ts.yp = 0; ts.count = 0; } s3c_adc_start(ts.client, 0, 1 << ts.shift); } else { ts.xp = 0; ts.yp = 0; ts.count = 0; input_report_key(ts.input, BTN_TOUCH, 0); input_sync(ts.input); writel(WAIT4INT | INT_DOWN, ts.io + S3C2410_ADCTSC); } }最后，我们可以看到触摸屏驱动是基于platform + input子系统 搭建起来的，正如搭积木一样，只要理解了每一个系统、部件的特点和接口等等，再稍加努力消化，就可把各式简单驱动程序的架构辨清，继而为自己编写驱动或者修改驱动打下了一个良好的基础。以上仅是菜鸟之愚见，还请前辈多多指教！