在內核中添加觸摸屏驅動程序

編者：linux2.6.32并沒有帶S3C2440觸摸屏驅動程序，需要自己實現。而在此的觸摸屏驅動程序時作為一個輸入設備來實現的。在linux中，對于輸入設備而言，內核專為其設計了輸入子系統，由核心層處理公共的工作。因為對于輸入設備而言，只是中斷、讀鍵值/坐標值是與設備相關的，其余的如輸入事件的緩沖區的管理以及字符設備驅動的file_operations接口則是輸入設備通用的。所以在此是在輸入子系統的框架下進行編寫觸摸屏驅動程序。對于這個驅動的移植以及講解，參考了網上的一些文章，一部分摒棄了手冊。

1 在內核中添加觸摸屏驅動程序

 Linux-2.6.32.2 內核也沒有包含支持S3C2440 的觸摸屏驅動，因此我們自行設計了一個s3c2410_ts.c，它位于linux-src/drivers/input/touchscreen 目錄下，你可以自己增加一個s3c2410_ts.c 文件，并復制如下內容：

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
/* For ts.dev.id.version */
#define S3C2410TSVERSION 0x0101
#define WAIT4INT(x) (((x)<<8) |
S3C2410_ADCTSC_YM_SEN | S3C2410_ADCTSC_YP_SEN | S3C2410_ADCTSC_XP_SEN |
S3C2410_ADCTSC_XY_PST(3))
#define AUTOPST (S3C2410_ADCTSC_YM_SEN | S3C2410_ADCTSC_YP_SEN |
S3C2410_ADCTSC_XP_SEN |
S3C2410_ADCTSC_AUTO_PST | S3C2410_ADCTSC_XY_PST(0))
static char *s3c2410ts_name = 's3c2410 TouchScreen';
static struct input_dev *dev;
static long xp;
static long yp;
static int count;
extern struct semaphore ADC_LOCK;
static int OwnADC = 0;
static void __iomem *base_addr;
static inline void s3c2410_ts_connect(void)
{
s3c2410_gpio_cfgpin(S3C2410_GPG(12), S3C2410_GPG12_XMON);
s3c2410_gpio_cfgpin(S3C2410_GPG(13), S3C2410_GPG13_nXPON);
s3c2410_gpio_cfgpin(S3C2410_GPG(14), S3C2410_GPG14_YMON);
s3c2410_gpio_cfgpin(S3C2410_GPG(15), S3C2410_GPG15_nYPON);
}
static void touch_timer_fire(unsigned long data)
{
unsigned long data0;
unsigned long data1;
int updown;
data0 = ioread32(base_addr+S3C2410_ADCDAT0);
data1 = ioread32(base_addr+S3C2410_ADCDAT1);
updown = (!(data0 & S3C2410_ADCDAT0_UPDOWN)) && (!(data1 & S3C2410_ADCDAT0_UPDOWN));
if (updown) {
if (count != 0) {
long tmp;
tmp = xp;
xp = yp;
yp = tmp;
xp >>= 2;
yp >>= 2;
input_report_abs(dev, ABS_X, xp);
input_report_abs(dev, ABS_Y, yp);
input_report_key(dev, BTN_TOUCH, 1);
input_report_abs(dev, ABS_PRESSURE, 1);
input_sync(dev);
}
xp = 0;
yp = 0;
count = 0;
iowrite32(S3C2410_ADCTSC_PULL_UP_DISABLE | AUTOPST, base_addr+S3C2410_ADCTSC);
iowrite32(ioread32(base_addr+S3C2410_ADCCON) | S3C2410_ADCCON_ENABLE_START,
base_addr+S3C2410_ADCCON);
} else {
count = 0;
input_report_key(dev, BTN_TOUCH, 0);
input_report_abs(dev, ABS_PRESSURE, 0);
input_sync(dev);
iowrite32(WAIT4INT(0), base_addr+S3C2410_ADCTSC);
if (OwnADC) {
OwnADC = 0;
up(&ADC_LOCK);
}
}
}
static struct timer_list touch_timer =
TIMER_INITIALIZER(touch_timer_fire, 0, 0);
static irqreturn_t stylus_updown(int irq, void *dev_id)
{
unsigned long data0;
unsigned long data1;
int updown;
if (down_trylock(&ADC_LOCK) == 0) {
OwnADC = 1;
data0 = ioread32(base_addr+S3C2410_ADCDAT0);
data1 = ioread32(base_addr+S3C2410_ADCDAT1);
updown = (!(data0 & S3C2410_ADCDAT0_UPDOWN)) && (!(data1 &
S3C2410_ADCDAT0_UPDOWN));
if (updown) {
touch_timer_fire(0);
} else {
OwnADC = 0;
up(&ADC_LOCK);
}
}
return IRQ_HANDLED;
}
static irqreturn_t stylus_action(int irq, void *dev_id)
{
unsigned long data0;
unsigned long data1;
if (OwnADC) {
data0 = ioread32(base_addr+S3C2410_ADCDAT0);
data1 = ioread32(base_addr+S3C2410_ADCDAT1);
xp += data0 & S3C2410_ADCDAT0_XPDATA_MASK;
yp += data1 & S3C2410_ADCDAT1_YPDATA_MASK;
count++;
if (count < (1<<2)) {
iowrite32(S3C2410_ADCTSC_PULL_UP_DISABLE | AUTOPST,
base_addr+S3C2410_ADCTSC);
iowrite32(ioread32(base_addr+S3C2410_ADCCON) | S3C2410_ADCCON_ENABLE_START,
base_addr+S3C2410_ADCCON);
} else {
mod_timer(&touch_timer, jiffies+1);
iowrite32(WAIT4INT(1), base_addr+S3C2410_ADCTSC);
}
}
return IRQ_HANDLED;
}
static struct clk *adc_clock;
static int __init s3c2410ts_init(void)
{
struct input_dev *input_dev;
adc_clock = clk_get(NULL, 'adc');
if (!adc_clock) {
printk(KERN_ERR 'failed to get adc clock sourcen');
return -ENOENT;
}
clk_enable(adc_clock);
base_addr=ioremap(S3C2410_PA_ADC,0x20);
if (base_addr == NULL) {
printk(KERN_ERR 'Failed to remap register blockn');
return -ENOMEM;
}
/* Configure GPIOs */
s3c2410_ts_connect();
iowrite32(S3C2410_ADCCON_PRSCEN | S3C2410_ADCCON_PRSCVL(0xFF),
base_addr+S3C2410_ADCCON);
iowrite32(0xffff, base_addr+S3C2410_ADCDLY);
iowrite32(WAIT4INT(0), base_addr+S3C2410_ADCTSC);
/* Initialise input stuff */
input_dev = input_allocate_device();
if (!input_dev) {
printk(KERN_ERR 'Unable to allocate the input device !!n');
return -ENOMEM;
}
dev = input_dev;
dev->evbit[0] = BIT(EV_SYN) | BIT(EV_KEY) | BIT(EV_ABS);
dev->keybit[BITS_TO_LONGS(BTN_TOUCH)] = BIT(BTN_TOUCH);
input_set_abs_params(dev, ABS_X, 0, 0x3FF, 0, 0);
input_set_abs_params(dev, ABS_Y, 0, 0x3FF, 0, 0);
input_set_abs_params(dev, ABS_PRESSURE, 0, 1, 0, 0);
dev->name = s3c2410ts_name;
dev->id.bustype = BUS_RS232;
dev->id.vendor = 0xDEAD;
dev->id.product = 0xBEEF;
dev->id.version = S3C2410TSVERSION;
/* Get irqs */
if (request_irq(IRQ_ADC, stylus_action, IRQF_SHARED|IRQF_SAMPLE_RANDOM,
's3c2410_action', dev)) {
printk(KERN_ERR 's3c2410_ts.c: Could not allocate ts IRQ_ADC !n');
iounmap(base_addr);
return -EIO;
}
if (request_irq(IRQ_TC, stylus_updown, IRQF_SAMPLE_RANDOM,
's3c2410_action', dev)) {
printk(KERN_ERR 's3c2410_ts.c: Could not allocate ts IRQ_TC !n');
iounmap(base_addr);
return -EIO;
}
printk(KERN_INFO '%s successfully loadedn', s3c2410ts_name);
/* All went ok, so register to the input system */
input_register_device(dev);
return 0;
}
static void __exit s3c2410ts_exit(void)
{
disable_irq(IRQ_ADC);
disable_irq(IRQ_TC);
free_irq(IRQ_TC,dev);
free_irq(IRQ_ADC,dev);
if (adc_clock) {
clk_disable(adc_clock);
clk_put(adc_clock);
adc_clock = NULL;
}
input_unregister_device(dev);
iounmap(base_addr);
}
module_init(s3c2410ts_init);
module_exit(s3c2410ts_exit);

然后在linux-2.6.32.2/drivers/input/touchscreen/Makefile 文件中添加該源代碼的目標模塊，如圖紅色部分：
obj-$(CONFIG_TOUCHSCREEN_WM97XX_ZYLONITE) += zylonite-wm97xx.o
obj-$(CONFIG_TOUCHSCREEN_W90X900) += w90p910_ts.o
obj-$(CONFIG_TOUCHSCREEN_PCAP) += pcap_ts.o
obj-$(CONFIG_TOUCHSCREEN_S3C2410) += s3c2410_ts.o

再打開linux-2.6.32.2/drivers/input/touchscreen/Kconfig 文件，加入如下紅色部分，這樣就在內核配置中添加了mini2440 的觸摸屏驅動選項：

menuconfig INPUT_TOUCHSCREEN
bool 'Touchscreens'
help
Say Y here, and a list of supported touchscreens will be displayed.
This option doesn't affect the kernel.
If unsure, say Y.
if INPUT_TOUCHSCREEN
config TOUCHSCREEN_S3C2410
tristate 'Samsung S3C2410 touchscreen input driver'
depends on MACH_MINI2440 && INPUT && INPUT_TOUCHSCREEN && MINI2440_ADC
help
Say Y here if you have the s3c2410 touchscreen.
If unsure, say N.
To compile this driver as a module, choose M here: the
module will be called s3c2410_ts.
config TOUCHSCREEN_ADS7846
tristate 'ADS7846/TSC2046 and ADS7843 based touchscreens'
depends on SPI_MASTER
depends on HWMON = n || HWMON
help

至此，我們就已經在內核中添加完了觸摸屏驅動。

2 配置編譯內核并測試觸摸屏驅動
在命令行執行：make menuconfig，然后依次選擇如下子菜單，找到剛剛添加的觸摸屏驅動選項：
Device Drivers --->
Input device support --->
[*] Touchscreens --->
按空格鍵選中觸摸屏驅動配置選項：退出并保存以上內核配置，在命令行輸入：make zImage，將生成arch/arm/boot/zImage文件，使用supervivi 的“k”命令把它燒寫到開發板。在此我們還是使用缺省的文件系統root_qtopia，可以看到屏幕上出現校正界面：依照屏幕提示，使用觸摸筆逐步點擊“十”型交叉點，即可進入qtopia 系統。

3、觸摸屏驅動程序的詳細分析。

這個內容由于較多，放在下一個文章里，見下鏈接。

linux-2.6.32在mini2440開發板上移植（10）之觸摸屏工作原理以及驅動程序詳細分析。 http://www.linuxidc.com/Linux/2013-04/82383p10.htm