S3C2410驅動分析之觸摸屏驅動

源碼路徑：drivers/input/touchscreen/s3c2410_ts.c

在Linux-2.6.36中,S3C2410對應的觸摸屏驅動程序是drivers/input/touchscreen/s3c2410_ts.c，本文對這個文件進行分析，詳細介紹相關知識點。S3C2410的觸摸屏驅動和ADC驅動緊密聯系在一起，在讀本文之前，請大家先看我的這篇《S3C2410驅動分析之ADC通用驅動》http://www.linuxidc.com/Linux/2012-04/58701.htm。

首先我們看模塊初始化函數：

436static int __init s3c2410ts_init(void)  
437{  
438    return platform_driver_register(&s3c_ts_driver);  
439}  
該驅動程序是以platform driver的方式注冊的，這裡注冊的platform_driver是s3c_ts_driver，其定義如下：

423static struct platform_driver s3c_ts_driver = {  
424    .driver         = {  
425        .name   = "samsung-ts",  
426        .owner  = THIS_MODULE,  
427#ifdef CONFIG_PM  
428        .pm = &s3c_ts_pmops,  
429#endif  
430    },  
431    .id_table   = s3cts_driver_ids,  
432    .probe      = s3c2410ts_probe,  
433    .remove     = __devexit_p(s3c2410ts_remove),  
434};  
這裡需要關注的是platform_driver結構的id_table和probe兩個成員。s3cts_driver_ids定義如下：

415static struct platform_device_id s3cts_driver_ids[] = {  
416    { "s3c2410-ts", 0 },  
417    { "s3c2440-ts", 0 },  
418    { "s3c64xx-ts", FEAT_PEN_IRQ },  
419    { }  
420};  
421MODULE_DEVICE_TABLE(platform, s3cts_driver_ids);

probe成員函數s3c2410ts_probe當模塊被加載時就會執行，其代碼如下：

234/** 
235 * s3c2410ts_probe - device core probe entry point 
236 * @pdev: The device we are being bound to. 
237 * 
238 * Initialise, find and allocate any resources we need to run and then 
239 * register with the ADC and input systems. 
240 */  
241static int __devinit s3c2410ts_probe(struct platform_device *pdev)  
242{  
243    struct s3c2410_ts_mach_info *info;  
244    struct device *dev = &pdev->dev;  
245    struct input_dev *input_dev;  
246    struct resource *res;  
247    int ret = -EINVAL;  
248  
249    /* Initialise input stuff */  
250    memset(&ts, 0, sizeof(struct s3c2410ts));  
251  
252    ts.dev = dev;  
253  
254    info = pdev->dev.platform_data;  
255    if (!info) {  
256        dev_err(dev, "no platform data, cannot attach\n");  
257        return -EINVAL;  
258    }  
259  
260    dev_dbg(dev, "initialising touchscreen\n");  
261  
262    ts.clock = clk_get(dev, "adc");  
263    if (IS_ERR(ts.clock)) {  
264        dev_err(dev, "cannot get adc clock source\n");  
265        return -ENOENT;  
266    }  
267  
268    clk_enable(ts.clock);  
269    dev_dbg(dev, "got and enabled clocks\n");  
270  
271    ts.irq_tc = ret = platform_get_irq(pdev, 0);  
272    if (ret < 0) {  
273        dev_err(dev, "no resource for interrupt\n");  
274        goto err_clk;  
275    }  
276  
277    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);  
278    if (!res) {  
279        dev_err(dev, "no resource for registers\n");  
280        ret = -ENOENT;  
281        goto err_clk;  
282    }  
283  
284    ts.io = ioremap(res->start, resource_size(res));  
285    if (ts.io == NULL) {  
286        dev_err(dev, "cannot map registers\n");  
287        ret = -ENOMEM;  
288        goto err_clk;  
289    }  
290  
291    /* inititalise the gpio */  
292    if (info->cfg_gpio)  
293        info->cfg_gpio(to_platform_device(ts.dev));  
294  
295    ts.client = s3c_adc_register(pdev, s3c24xx_ts_select,  
296                     s3c24xx_ts_conversion, 1);  
297    if (IS_ERR(ts.client)) {  
298        dev_err(dev, "failed to register adc client\n");  
299        ret = PTR_ERR(ts.client);  
300        goto err_iomap;  
301    }  
302  
303    /* Initialise registers */  
304    if ((info->delay & 0xffff) > 0)  
305        writel(info->delay & 0xffff, ts.io + S3C2410_ADCDLY);  
306  
307    writel(WAIT4INT | INT_DOWN, ts.io + S3C2410_ADCTSC);  
308  
309    input_dev = input_allocate_device();  
310    if (!input_dev) {  
311        dev_err(dev, "Unable to allocate the input device !!\n");  
312        ret = -ENOMEM;  
313        goto err_iomap;  
314    }  
315  
316    ts.input = input_dev;  
317    ts.input->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);  
318    ts.input->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);  
319    input_set_abs_params(ts.input, ABS_X, 0, 0x3FF, 0, 0);  
320    input_set_abs_params(ts.input, ABS_Y, 0, 0x3FF, 0, 0);  
321  
322    ts.input->name = "S3C24XX TouchScreen";  
323    ts.input->id.bustype = BUS_HOST;  
324    ts.input->id.vendor = 0xDEAD;  
325    ts.input->id.product = 0xBEEF;  
326    ts.input->id.version = 0x0102;  
327  
328    ts.shift = info->oversampling_shift;  
329    ts.features = platform_get_device_id(pdev)->driver_data;  
330  
331    ret = request_irq(ts.irq_tc, stylus_irq, IRQF_DISABLED,  
332              "s3c2410_ts_pen", ts.input);  
333    if (ret) {  
334        dev_err(dev, "cannot get TC interrupt\n");  
335        goto err_inputdev;  
336    }  
337  
338    dev_info(dev, "driver attached, registering input device\n");  
339  
340    /* All went ok, so register to the input system */  
341    ret = input_register_device(ts.input);  
342    if (ret < 0) {  
343        dev_err(dev, "failed to register input device\n");  
344        ret = -EIO;  
345        goto err_tcirq;  
346    }  
347  
348    return 0;  
349  
350 err_tcirq:  
351    free_irq(ts.irq_tc, ts.input);  
352 err_inputdev:  
353    input_unregister_device(ts.input);  
354 err_iomap:  
355    iounmap(ts.io);  
356 err_clk:  
357    del_timer_sync(&touch_timer);  
358    clk_put(ts.clock);  
359    return ret;  
360}  
243行，定義s3c2410_ts_mach_info結構體變量info，該結構體定義在arch/arm/plat-samsung/include/plat/ts.h文件中：

13struct s3c2410_ts_mach_info {  
14       int             delay;  
15       int             presc;  
16       int             oversampling_shift;  
17    void    (*cfg_gpio)(struct platform_device *dev);  
18};  
delay保存ADC的延遲時間。

presc保存ADC的預分頻系數。

oversampling_shift保存采樣次數log2值。

cfg_gpio函數用於設置gpio。

250行，將ts清0，ts是s3c2410ts結構體類型變量，其定義如下：

62/** 
63 * struct s3c2410ts - driver touchscreen state. 
64 * @client: The ADC client we registered with the core driver. 
65 * @dev: The device we are bound to. 
66 * @input: The input device we registered with the input subsystem. 
67 * @clock: The clock for the adc. 
68 * @io: Pointer to the IO base. 
69 * @xp: The accumulated X position data. 
70 * @yp: The accumulated Y position data. 
71 * @irq_tc: The interrupt number for pen up/down interrupt 
72 * @count: The number of samples collected. 
73 * @shift: The log2 of the maximum count to read in one go. 
74 * @features: The features supported by the TSADC MOdule. 
75 */  
76struct s3c2410ts {  
77    struct s3c_adc_client *client;  
78    struct device *dev;  
79    struct input_dev *input;  
80    struct clk *clock;  
81    void __iomem *io;  
82    unsigned long xp;  
83    unsigned long yp;  
84    int irq_tc;  
85    int count;  
86    int shift;  
87    int features;  
88};  
89  
90static struct s3c2410ts ts;  
s3c2410ts結構體的各個成員的含義在注冊中已經說的很清楚，這裡不再解釋。