字符设备，杂项设备虽然简单，但是在工程中，比如SDK中，通常都使用platform设备驱动来实现硬件驱动，为什么呢？先看看platform设备驱动的结构：
platform由两部分组成：设备--platform_device和驱动--platform_driver。它们之间通过platform总线来绑定，这个我们不需要关心，内核里面的东西。
platform总线是一个虚拟的总线，跟其他总线（比如：I2C,SPI,USB,PCIE）一样，当系统注册一个设备（platform_device）的时候，会通过它去寻找与之匹配的驱动（platform_driver）；当注册一个驱动(platform_driver)的时候，也会通过platform总线去寻找一个相应的设备（platform_device）。
platform设备在注册的时候，将其使用的资源也注册进去，由内核统一管理，在 驱动程序 使用这些资源时 使用统一的接口，这样提高了程序的可移植性。
好吧，看看相关的结构体吧。
1 struct platform_device {
2
3 const char * name ; /* 设备名 */
4
5 int id ; // 设备名编号， 配合设备名使用
6
7 struct device dev ;
8
9 u32 num_resources ;
10
11 struct resource * resource ; /* 设备资源 */
12
13 }
14
15 struct resource {
16
17 resource_size_t start; /* 资源的起始物理地址 */
18
19 resource_size_t end; <span style="font-family: Arial, Helvetica, sans-serif; font-size: 12px;">/* 资源的结束物理地址 */
20
21 const char *name; /* 资源的名称 */
22
23 unsigned long flags; /* 资源的类型，比如MEM ，IO，IRQ类型 */
24
25 struct resource *parent, *sibling, *child; /* 资源链表指针 */
26
27 };
28
29 struct platform_driver {
30
31 int (*probe)(struct platform_device *);
32
33 int (*remove)(struct platform_device *);
34
35 void (*shutdown)(struct platform_device *);
36
37 int (*suspend)(struct platform_device *, pm_message_t state);
38
39 int (*suspend_late)(struct platform_device *, pm_message_t state);
40
41 int (*resume_early)(struct platform_device *);
42
43 int (*resume)(struct platform_device *);
44
45 struct device_driver driver;
46
47 };
这就是最基础的三个结构体，把这三个结构体里面的部分或全部成员填满，一个platform设备驱动就基本完成了。
和字符驱动一样，看流程吧：
1，先定义，再注册device，一般的我们可以放在板文件里。
在dev-rtc.c文件中：
1 static struct resource s3c_rtc_resource[] = {
2 [0] = {
3 .start = S3C_PA_RTC,
4 .end = S3C_PA_RTC + 0xff,
5 .flags = IORESOURCE_MEM,
6 },
7 [1] = {
8 .start = IRQ_RTC_ALARM,
9 .end = IRQ_RTC_ALARM,
10 .flags = IORESOURCE_IRQ,
11 },
12 [2] = {
13 .start = IRQ_RTC_TIC,
14 .end = IRQ_RTC_TIC,
15 .flags = IORESOURCE_IRQ
16 }
17 };
18
19 struct platform_device s3c_device_rtc = {
20 .name = "s3c64xx-rtc",
21 .id = -1,
22 .num_resources = ARRAY_SIZE(s3c_rtc_resource),
23 .resource = s3c_rtc_resource,
24 };
25 EXPORT_SYMBOL(s3c_device_rtc);
在这里我们看到一个设备struct platform_device s3c_device_rtc，以及它用到的resource。刚我说了，一般device是在板级文件中定义和注册，但是这个是作为系统的rtc，它就有了它专门定义的文件，但是它在这里导出（EXPORT_SYMBOL(s3c_device_rtc)），注册在哪呢？这回真的在板文件了
1 /* Add platform device */
2 static struct platform_device *xc2440_devices[] __initdata = {
3 &s3c_device_nand,
4 &s3c_device_lcd,
5 &s3c_device_adc,
6 &s3c_device_hwmon,
7 &s3c_device_ts,
8 &xc2440_ethernet_device,
9 &s3c_device_ohci,
10 &s3c_device_usbgadget,
11 &s3c_device_timer[0],
12 &s3c_device_timer[1],
13 &xc2440_backlight_device,
14 &xc2440_beeper_device,
15 &xc2440_device_led,
16 &xc2440_button_device,
17 &s3c_device_i2c0,
18 &s3c_device_rtc,
19 &s3c_device_wdt,
20 &s3c_device_sdi,
21 &s3c_device_iis,
22 &xc2440_audio_device,
23 &xc2440_ds18b20_device,
24 &xc2440_irm_device,
25
26 /* &s3c_device_spi0,
27 &s3c_device_spi1,
28 &s3c_device_camif,
29 &xc2440_spi_gpio, */
30
31 };
我们看到rtc的device在一个platform_device的数列里面，这样便于我们理解和移植。还是没注册啊~怎么那么啰嗦
1 static void __init xc2440_machine_init(void)
2 {
3 s3c24xx_fb_set_platdata(&xc2440_fb_info);
4 s3c_i2c0_set_platdata(NULL);
5 s3c_nand_set_platdata(&xc2440_nand_info);
6 s3c24xx_mci_set_platdata(&xc2440_mmc_cfg);
7 s3c_hwmon_set_platdata(&xc2440_hwmon_info);
8 s3c24xx_ts_set_platdata(&xc2440_ts_cfg);
9 i2c_register_board_info(0, xc2440_i2c_devs,ARRAY_SIZE(xc2440_i2c_devs));
10 s3c24xx_udc_set_platdata(&xc2440_udc_cfg);
11
12 spi_register_board_info(xc2440_spi_board_info, ARRAY_SIZE(xc2440_spi_board_info));
13 platform_add_devices(xc2440_devices, ARRAY_SIZE(xc2440_devices));
14 }
终于注册进去了、、、、、、、、
下面是应用中的一个设备定义，注册已经在上面了：
1 /* IRM3638 */
2 static struct platform_xc2440_irm_data xc2440_irm_pins = {
3 .ctrl_pin_irq = IRQ_EINT(11),
4 .irq_type = IRQF_TRIGGER_FALLING,
5 };
6
7
8 static struct platform_device xc2440_irm_device = {
9 .name = "xc2440-irm",
10 .id = -1,
11 .dev = {
12 .platform_data = &xc2440_irm_pins,
13 },
14 };
这个platform_device就没有resources，因为它不使用。但是它多了一个自己定义的结构体platform_xc2440_irm_data，作为与驱动交换数据。
2，platform_driver的编写。
实现跟字符驱动没什么区别，都需要完成file_operations这个结构体的成员函数。但是字符驱动的注册和卸载，放到了platform_driver结构体的probe和remove函数里。而驱动本身的注册和卸载就用到了platform_driver_register和platform_driver_unregister。
看一个刚才s3c的rtc程序，关于rtc相关的函数先略掉，主要看架构：
1 /* drivers/rtc/rtc-s3c.c
2 *
3 * Copyright (c) 2010 Samsung Electronics Co., Ltd.
4 * http://www.samsung.com/
5 *
6 * Copyright (c) 2004,2006 Simtec Electronics
7 * Ben Dooks, <[email protected]>
8 * http://armlinux.simtec.co.uk/
9 *
10 * This program is free software; you can redistribute it and/or modify
11 * it under the terms of the GNU General Public License version 2 as
12 * published by the Free Software Foundation.
13 *
14 * S3C2410/S3C2440/S3C24XX Internal RTC Driver
15 */
16
17 #include <linux/module.h>
18 #include <linux/fs.h>
19 #include <linux/string.h>
20 #include <linux/init.h>
21 #include <linux/platform_device.h>
22 #include <linux/interrupt.h>
23 #include <linux/rtc.h>
24 #include <linux/bcd.h>
25 #include <linux/clk.h>
26 #include <linux/log2.h>
27 #include <linux/slab.h>
28
29 #include <mach/hardware.h>
30 #include <asm/uaccess.h>
31 #include <asm/io.h>
32 #include <asm/irq.h>
33 #include <plat/regs-rtc.h>
34
35 enum s3c_cpu_type {
36 TYPE_S3C2410,
37 TYPE_S3C64XX,
38 };
39
40 /* I have yet to find an S3C implementation with more than one
41 * of these rtc blocks in */
42
43 static struct resource *s3c_rtc_mem;
44
45 static struct clk *rtc_clk;
46 static void __iomem *s3c_rtc_base;
47 static int s3c_rtc_alarmno = NO_IRQ;
48 static int s3c_rtc_tickno = NO_IRQ;
49 static enum s3c_cpu_type s3c_rtc_cpu_type;
50
51 static DEFINE_SPINLOCK(s3c_rtc_pie_lock);
52
53 /* IRQ Handlers */
54
55 static irqreturn_t s3c_rtc_alarmirq(int irq, void *id)
56 {
57 struct rtc_device *rdev = id;
58
59 rtc_update_irq(rdev, 1, RTC_AF | RTC_IRQF);
60
61 if (s3c_rtc_cpu_type == TYPE_S3C64XX)
62 writeb(S3C2410_INTP_ALM, s3c_rtc_base + S3C2410_INTP);
63
64 return IRQ_HANDLED;
65 }
66
67 static irqreturn_t s3c_rtc_tickirq(int irq, void *id)
68 {
69 struct rtc_device *rdev = id;
70
71 rtc_update_irq(rdev, 1, RTC_PF | RTC_IRQF);
72
73 if (s3c_rtc_cpu_type == TYPE_S3C64XX)
74 writeb(S3C2410_INTP_TIC, s3c_rtc_base + S3C2410_INTP);
75
76 return IRQ_HANDLED;
77 }
78
79 /* Update control registers */
80 static void s3c_rtc_setaie(int to)
81 {
82 unsigned int tmp;
83
84 pr_debug("%s: aie=%d\n", __func__, to);
85
86 tmp = readb(s3c_rtc_base + S3C2410_RTCALM) & ~S3C2410_RTCALM_ALMEN;
87
88 if (to)
89 tmp |= S3C2410_RTCALM_ALMEN;
90
91 writeb(tmp, s3c_rtc_base + S3C2410_RTCALM);
92 }
93
94 static int s3c_rtc_setpie(struct device *dev, int enabled)
95 {
96 unsigned int tmp;
97
98 pr_debug("%s: pie=%d\n", __func__, enabled);
99
100 spin_lock_irq(&s3c_rtc_pie_lock);
101
102 if (s3c_rtc_cpu_type == TYPE_S3C64XX) {
103 tmp = readw(s3c_rtc_base + S3C2410_RTCCON);
104 tmp &= ~S3C64XX_RTCCON_TICEN;
105
106 if (enabled)
107 tmp |= S3C64XX_RTCCON_TICEN;
108
109 writew(tmp, s3c_rtc_base + S3C2410_RTCCON);
110 } else {
111 tmp = readb(s3c_rtc_base + S3C2410_TICNT);
112 tmp &= ~S3C2410_TICNT_ENABLE;
113
114 if (enabled)
115 tmp |= S3C2410_TICNT_ENABLE;
116
117 writeb(tmp, s3c_rtc_base + S3C2410_TICNT);
118 }
119
120 spin_unlock_irq(&s3c_rtc_pie_lock);
121
122 return 0;
123 }
124
125 static int s3c_rtc_setfreq(struct device *dev, int freq)
126 {
127 struct platform_device *pdev = to_platform_device(dev);
128 struct rtc_device *rtc_dev = platform_get_drvdata(pdev);
129 unsigned int tmp = 0;
130
131 if (!is_power_of_2(freq))
132 return -EINVAL;
133
134 spin_lock_irq(&s3c_rtc_pie_lock);
135
136 if (s3c_rtc_cpu_type == TYPE_S3C2410) {
137 tmp = readb(s3c_rtc_base + S3C2410_TICNT);
138 tmp &= S3C2410_TICNT_ENABLE;
139 }
140
141 tmp |= (rtc_dev->max_user_freq / freq)-1;
142
143 writel(tmp, s3c_rtc_base + S3C2410_TICNT);
144 spin_unlock_irq(&s3c_rtc_pie_lock);
145
146 return 0;
147 }
148
149 /* Time read/write */
150
151 static int s3c_rtc_gettime(struct device *dev, struct rtc_time *rtc_tm)
152 {
153 unsigned int have_retried = 0;
154 void __iomem *base = s3c_rtc_base;
155
156 retry_get_time:
157 rtc_tm->tm_min = readb(base + S3C2410_RTCMIN);
158 rtc_tm->tm_hour = readb(base + S3C2410_RTCHOUR);
159 rtc_tm->tm_mday = readb(base + S3C2410_RTCDATE);
160 rtc_tm->tm_mon = readb(base + S3C2410_RTCMON);
161 rtc_tm->tm_year = readb(base + S3C2410_RTCYEAR);
162 rtc_tm->tm_sec = readb(base + S3C2410_RTCSEC);
163
164 /* the only way to work out wether the system was mid-update
165 * when we read it is to check the second counter, and if it
166 * is zero, then we re-try the entire read
167 */
168
169 if (rtc_tm->tm_sec == 0 && !have_retried) {
170 have_retried = 1;
171 goto retry_get_time;
172 }
173
174 pr_debug("read time %04d.%02d.%02d %02d:%02d:%02d\n",
175 1900 + rtc_tm->tm_year, rtc_tm->tm_mon, rtc_tm->tm_mday,
176 rtc_tm->tm_hour, rtc_tm->tm_min, rtc_tm->tm_sec);
177
178 rtc_tm->tm_sec = bcd2bin(rtc_tm->tm_sec);
179 rtc_tm->tm_min = bcd2bin(rtc_tm->tm_min);
180 rtc_tm->tm_hour = bcd2bin(rtc_tm->tm_hour);
181 rtc_tm->tm_mday = bcd2bin(rtc_tm->tm_mday);
182 rtc_tm->tm_mon = bcd2bin(rtc_tm->tm_mon);
183 rtc_tm->tm_year = bcd2bin(rtc_tm->tm_year);
184
185 rtc_tm->tm_year += 100;
186 rtc_tm->tm_mon -= 1;
187
188 return rtc_valid_tm(rtc_tm);
189 }
190
191 static int s3c_rtc_settime(struct device *dev, struct rtc_time *tm)
192 {
193 void __iomem *base = s3c_rtc_base;
194 int year = tm->tm_year - 100;
195
196 pr_debug("set time %04d.%02d.%02d %02d:%02d:%02d\n",
197 1900 + tm->tm_year, tm->tm_mon, tm->tm_mday,
198 tm->tm_hour, tm->tm_min, tm->tm_sec);
199
200 /* we get around y2k by simply not supporting it */
201
202 if (year < 0 || year >= 100) {
203 dev_err(dev, "rtc only supports 100 years\n");
204 return -EINVAL;
205 }
206
207 writeb(bin2bcd(tm->tm_sec), base + S3C2410_RTCSEC);
208 writeb(bin2bcd(tm->tm_min), base + S3C2410_RTCMIN);
209 writeb(bin2bcd(tm->tm_hour), base + S3C2410_RTCHOUR);
210 writeb(bin2bcd(tm->tm_mday), base + S3C2410_RTCDATE);
211 writeb(bin2bcd(tm->tm_mon + 1), base + S3C2410_RTCMON);
212 writeb(bin2bcd(year), base + S3C2410_RTCYEAR);
213
214 return 0;
215 }
216
217 static int s3c_rtc_getalarm(struct device *dev, struct rtc_wkalrm *alrm)
218 {
219 struct rtc_time *alm_tm = &alrm->time;
220 void __iomem *base = s3c_rtc_base;
221 unsigned int alm_en;
222
223 alm_tm->tm_sec = readb(base + S3C2410_ALMSEC);
224 alm_tm->tm_min = readb(base + S3C2410_ALMMIN);
225 alm_tm->tm_hour = readb(base + S3C2410_ALMHOUR);
226 alm_tm->tm_mon = readb(base + S3C2410_ALMMON);
227 alm_tm->tm_mday = readb(base + S3C2410_ALMDATE);
228 alm_tm->tm_year = readb(base + S3C2410_ALMYEAR);
229
230 alm_en = readb(base + S3C2410_RTCALM);
231
232 alrm->enabled = (alm_en & S3C2410_RTCALM_ALMEN) ? 1 : 0;
233
234 pr_debug("read alarm %d, %04d.%02d.%02d %02d:%02d:%02d\n",
235 alm_en,
236 1900 + alm_tm->tm_year, alm_tm->tm_mon, alm_tm->tm_mday,
237 alm_tm->tm_hour, alm_tm->tm_min, alm_tm->tm_sec);
238
239
240 /* decode the alarm enable field */
241
242 if (alm_en & S3C2410_RTCALM_SECEN)
243 alm_tm->tm_sec = bcd2bin(alm_tm->tm_sec);
244 else
245 alm_tm->tm_sec = -1;
246
247 if (alm_en & S3C2410_RTCALM_MINEN)
248 alm_tm->tm_min = bcd2bin(alm_tm->tm_min);
249 else
250 alm_tm->tm_min = -1;
251
252 if (alm_en & S3C2410_RTCALM_HOUREN)
253 alm_tm->tm_hour = bcd2bin(alm_tm->tm_hour);
254 else
255 alm_tm->tm_hour = -1;
256
257 if (alm_en & S3C2410_RTCALM_DAYEN)
258 alm_tm->tm_mday = bcd2bin(alm_tm->tm_mday);
259 else
260 alm_tm->tm_mday = -1;
261
262 if (alm_en & S3C2410_RTCALM_MONEN) {
263 alm_tm->tm_mon = bcd2bin(alm_tm->tm_mon);
264 alm_tm->tm_mon -= 1;
265 } else {
266 alm_tm->tm_mon = -1;
267 }
268
269 if (alm_en & S3C2410_RTCALM_YEAREN)
270 alm_tm->tm_year = bcd2bin(alm_tm->tm_year);
271 else
272 alm_tm->tm_year = -1;
273
274 return 0;
275 }
276
277 static int s3c_rtc_setalarm(struct device *dev, struct rtc_wkalrm *alrm)
278 {
279 struct rtc_time *tm = &alrm->time;
280 void __iomem *base = s3c_rtc_base;
281 unsigned int alrm_en;
282
283 pr_debug("s3c_rtc_setalarm: %d, %04d.%02d.%02d %02d:%02d:%02d\n",
284 alrm->enabled,
285 1900 + tm->tm_year, tm->tm_mon, tm->tm_mday,
286 tm->tm_hour, tm->tm_min, tm->tm_sec);
287
288
289 alrm_en = readb(base + S3C2410_RTCALM) & S3C2410_RTCALM_ALMEN;
290 writeb(0x00, base + S3C2410_RTCALM);
291
292 if (tm->tm_sec < 60 && tm->tm_sec >= 0) {
293 alrm_en |= S3C2410_RTCALM_SECEN;
294 writeb(bin2bcd(tm->tm_sec), base + S3C2410_ALMSEC);
295 }
296
297 if (tm->tm_min < 60 && tm->tm_min >= 0) {
298 alrm_en |= S3C2410_RTCALM_MINEN;
299 writeb(bin2bcd(tm->tm_min), base + S3C2410_ALMMIN);
300 }
301
302 if (tm->tm_hour < 24 && tm->tm_hour >= 0) {
303 alrm_en |= S3C2410_RTCALM_HOUREN;
304 writeb(bin2bcd(tm->tm_hour), base + S3C2410_ALMHOUR);
305 }
306
307 pr_debug("setting S3C2410_RTCALM to %08x\n", alrm_en);
308
309 writeb(alrm_en, base + S3C2410_RTCALM);
310
311 s3c_rtc_setaie(alrm->enabled);
312
313 return 0;
314 }
315
316 static int s3c_rtc_proc(struct device *dev, struct seq_file *seq)
317 {
318 unsigned int ticnt;
319
320 if (s3c_rtc_cpu_type == TYPE_S3C64XX) {
321 ticnt = readw(s3c_rtc_base + S3C2410_RTCCON);
322 ticnt &= S3C64XX_RTCCON_TICEN;
323 } else {
324 ticnt = readb(s3c_rtc_base + S3C2410_TICNT);
325 ticnt &= S3C2410_TICNT_ENABLE;
326 }
327
328 seq_printf(seq, "periodic_IRQ\t: %s\n", ticnt ? "yes" : "no");
329 return 0;
330 }
331
332 static int s3c_rtc_open(struct device *dev)
333 {
334 struct platform_device *pdev = to_platform_device(dev);
335 struct rtc_device *rtc_dev = platform_get_drvdata(pdev);
336 int ret;
337
338 ret = request_irq(s3c_rtc_alarmno, s3c_rtc_alarmirq,
339 IRQF_DISABLED, "s3c2410-rtc alarm", rtc_dev);
340
341 if (ret) {
342 dev_err(dev, "IRQ%d error %d\n", s3c_rtc_alarmno, ret);
343 return ret;
344 }
345
346 ret = request_irq(s3c_rtc_tickno, s3c_rtc_tickirq,
347 IRQF_DISABLED, "s3c2410-rtc tick", rtc_dev);
348
349 if (ret) {
350 dev_err(dev, "IRQ%d error %d\n", s3c_rtc_tickno, ret);
351 goto tick_err;
352 }
353
354 return ret;
355
356 tick_err:
357 free_irq(s3c_rtc_alarmno, rtc_dev);
358 return ret;
359 }
360
361 static void s3c_rtc_release(struct device *dev)
362 {
363 struct platform_device *pdev = to_platform_device(dev);
364 struct rtc_device *rtc_dev = platform_get_drvdata(pdev);
365
366 /* do not clear AIE here, it may be needed for wake */
367
368 s3c_rtc_setpie(dev, 0);
369 free_irq(s3c_rtc_alarmno, rtc_dev);
370 free_irq(s3c_rtc_tickno, rtc_dev);
371 }
372
373 static const struct rtc_class_ops s3c_rtcops = {
374 .open = s3c_rtc_open,
375 .release = s3c_rtc_release,
376 .read_time = s3c_rtc_gettime,
377 .set_time = s3c_rtc_settime,
378 .read_alarm = s3c_rtc_getalarm,
379 .set_alarm = s3c_rtc_setalarm,
380 .irq_set_freq = s3c_rtc_setfreq,
381 .irq_set_state = s3c_rtc_setpie,
382 .proc = s3c_rtc_proc,
383 .alarm_irq_enable = s3c_rtc_setaie,
384 };
385
386 static void s3c_rtc_enable(struct platform_device *pdev, int en)
387 {
388 void __iomem *base = s3c_rtc_base;
389 unsigned int tmp;
390
391 if (s3c_rtc_base == NULL)
392 return;
393
394 if (!en) {
395 tmp = readw(base + S3C2410_RTCCON);
396 if (s3c_rtc_cpu_type == TYPE_S3C64XX)
397 tmp &= ~S3C64XX_RTCCON_TICEN;
398 tmp &= ~S3C2410_RTCCON_RTCEN;
399 writew(tmp, base + S3C2410_RTCCON);
400
401 if (s3c_rtc_cpu_type == TYPE_S3C2410) {
402 tmp = readb(base + S3C2410_TICNT);
403 tmp &= ~S3C2410_TICNT_ENABLE;
404 writeb(tmp, base + S3C2410_TICNT);
405 }
406 } else {
407 /* re-enable the device, and check it is ok */
408
409 if ((readw(base+S3C2410_RTCCON) & S3C2410_RTCCON_RTCEN) == 0) {
410 dev_info(&pdev->dev, "rtc disabled, re-enabling\n");
411
412 tmp = readw(base + S3C2410_RTCCON);
413 writew(tmp | S3C2410_RTCCON_RTCEN,
414 base + S3C2410_RTCCON);
415 }
416
417 if ((readw(base + S3C2410_RTCCON) & S3C2410_RTCCON_CNTSEL)) {
418 dev_info(&pdev->dev, "removing RTCCON_CNTSEL\n");
419
420 tmp = readw(base + S3C2410_RTCCON);
421 writew(tmp & ~S3C2410_RTCCON_CNTSEL,
422 base + S3C2410_RTCCON);
423 }
424
425 if ((readw(base + S3C2410_RTCCON) & S3C2410_RTCCON_CLKRST)) {
426 dev_info(&pdev->dev, "removing RTCCON_CLKRST\n");
427
428 tmp = readw(base + S3C2410_RTCCON);
429 writew(tmp & ~S3C2410_RTCCON_CLKRST,
430 base + S3C2410_RTCCON);
431 }
432 }
433 }
434
435 static int __devexit s3c_rtc_remove(struct platform_device *dev)
436 {
437 struct rtc_device *rtc = platform_get_drvdata(dev);
438
439 platform_set_drvdata(dev, NULL);
440 rtc_device_unregister(rtc);
441
442 s3c_rtc_setpie(&dev->dev, 0);
443 s3c_rtc_setaie(0);
444
445 clk_disable(rtc_clk);
446 clk_put(rtc_clk);
447 rtc_clk = NULL;
448
449 iounmap(s3c_rtc_base);
450 release_resource(s3c_rtc_mem);
451 kfree(s3c_rtc_mem);
452
453 return 0;
454 }
455
456 static int __devinit s3c_rtc_probe(struct platform_device *pdev)
457 {
458 struct rtc_device *rtc;
459 struct rtc_time rtc_tm;
460 struct resource *res;
461 int ret;
462
463 pr_debug("%s: probe=%p\n", __func__, pdev);
464
465 /* find the IRQs */
466
467 s3c_rtc_tickno = platform_get_irq(pdev, 1);
468 if (s3c_rtc_tickno < 0) {
469 dev_err(&pdev->dev, "no irq for rtc tick\n");
470 return -ENOENT;
471 }
472
473 s3c_rtc_alarmno = platform_get_irq(pdev, 0);
474 if (s3c_rtc_alarmno < 0) {
475 dev_err(&pdev->dev, "no irq for alarm\n");
476 return -ENOENT;
477 }
478
479 pr_debug("s3c2410_rtc: tick irq %d, alarm irq %d\n",
480 s3c_rtc_tickno, s3c_rtc_alarmno);
481
482 /* get the memory region */
483
484 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
485 if (res == NULL) {
486 dev_err(&pdev->dev, "failed to get memory region resource\n");
487 return -ENOENT;
488 }
489
490 s3c_rtc_mem = request_mem_region(res->start,
491 res->end-res->start+1,
492 pdev->name);
493
494 if (s3c_rtc_mem == NULL) {
495 dev_err(&pdev->dev, "failed to reserve memory region\n");
496 ret = -ENOENT;
497 goto err_nores;
498 }
499
500 s3c_rtc_base = ioremap(res->start, res->end - res->start + 1);
501 if (s3c_rtc_base == NULL) {
502 dev_err(&pdev->dev, "failed ioremap()\n");
503 ret = -EINVAL;
504 goto err_nomap;
505 }
506
507 rtc_clk = clk_get(&pdev->dev, "rtc");
508 if (IS_ERR(rtc_clk)) {
509 dev_err(&pdev->dev, "failed to find rtc clock source\n");
510 ret = PTR_ERR(rtc_clk);
511 rtc_clk = NULL;
512 goto err_clk;
513 }
514
515 clk_enable(rtc_clk);
516
517 /* check to see if everything is setup correctly */
518
519 s3c_rtc_enable(pdev, 1);
520
521 pr_debug("s3c2410_rtc: RTCCON=%02x\n",
522 readw(s3c_rtc_base + S3C2410_RTCCON));
523
524 device_init_wakeup(&pdev->dev, 1);
525
526 /* register RTC and exit */
527
528 rtc = rtc_device_register("s3c", &pdev->dev, &s3c_rtcops,
529 THIS_MODULE);
530
531 if (IS_ERR(rtc)) {
532 dev_err(&pdev->dev, "cannot attach rtc\n");
533 ret = PTR_ERR(rtc);
534 goto err_nortc;
535 }
536
537 s3c_rtc_cpu_type = platform_get_device_id(pdev)->driver_data;
538
539 /* Check RTC Time */
540
541 s3c_rtc_gettime(NULL, &rtc_tm);
542
543 if (rtc_valid_tm(&rtc_tm)) {
544 rtc_tm.tm_year = 100;
545 rtc_tm.tm_mon = 0;
546 rtc_tm.tm_mday = 1;
547 rtc_tm.tm_hour = 0;
548 rtc_tm.tm_min = 0;
549 rtc_tm.tm_sec = 0;
550
551 s3c_rtc_settime(NULL, &rtc_tm);
552
553 dev_warn(&pdev->dev, "warning: invalid RTC value so initializing it\n");
554 }
555
556 if (s3c_rtc_cpu_type == TYPE_S3C64XX)
557 rtc->max_user_freq = 32768;
558 else
559 rtc->max_user_freq = 128;
560
561 platform_set_drvdata(pdev, rtc);
562
563 s3c_rtc_setfreq(&pdev->dev, 1);
564
565 return 0;
566
567 err_nortc:
568 s3c_rtc_enable(pdev, 0);
569 clk_disable(rtc_clk);
570 clk_put(rtc_clk);
571
572 err_clk:
573 iounmap(s3c_rtc_base);
574
575 err_nomap:
576 release_resource(s3c_rtc_mem);
577
578 err_nores:
579 return ret;
580 }
581
582 #ifdef CONFIG_PM
583
584 /* RTC Power management control */
585
586 static int ticnt_save, ticnt_en_save;
587
588 static int s3c_rtc_suspend(struct platform_device *pdev, pm_message_t state)
589 {
590 /* save TICNT for anyone using periodic interrupts */
591 ticnt_save = readb(s3c_rtc_base + S3C2410_TICNT);
592 if (s3c_rtc_cpu_type == TYPE_S3C64XX) {
593 ticnt_en_save = readw(s3c_rtc_base + S3C2410_RTCCON);
594 ticnt_en_save &= S3C64XX_RTCCON_TICEN;
595 }
596 s3c_rtc_enable(pdev, 0);
597
598 if (device_may_wakeup(&pdev->dev))
599 enable_irq_wake(s3c_rtc_alarmno);
600
601 return 0;
602 }
603
604 static int s3c_rtc_resume(struct platform_device *pdev)
605 {
606 unsigned int tmp;
607
608 s3c_rtc_enable(pdev, 1);
609 writeb(ticnt_save, s3c_rtc_base + S3C2410_TICNT);
610 if (s3c_rtc_cpu_type == TYPE_S3C64XX && ticnt_en_save) {
611 tmp = readw(s3c_rtc_base + S3C2410_RTCCON);
612 writew(tmp | ticnt_en_save, s3c_rtc_base + S3C2410_RTCCON);
613 }
614
615 if (device_may_wakeup(&pdev->dev))
616 disable_irq_wake(s3c_rtc_alarmno);
617
618 return 0;
619 }
620 #else
621 #define s3c_rtc_suspend NULL
622 #define s3c_rtc_resume NULL
623 #endif
624
625 static struct platform_device_id s3c_rtc_driver_ids[] = {
626 {
627 .name = "s3c2410-rtc",
628 .driver_data = TYPE_S3C2410,
629 }, {
630 .name = "s3c64xx-rtc",
631 .driver_data = TYPE_S3C64XX,
632 },
633 { }
634 };
635
636 MODULE_DEVICE_TABLE(platform, s3c_rtc_driver_ids);
637
638 static struct platform_driver s3c_rtc_driver = {
639 .probe = s3c_rtc_probe,
640 .remove = __devexit_p(s3c_rtc_remove),
641 .suspend = s3c_rtc_suspend,
642 .resume = s3c_rtc_resume,
643 .id_table = s3c_rtc_driver_ids,
644 .driver = {
645 .name = "s3c-rtc",
646 .owner = THIS_MODULE,
647 },
648 };
649
650 static char __initdata banner[] = "S3C24XX RTC, (c) 2004,2006 Simtec Electronics\n";
651
652 static int __init s3c_rtc_init(void)
653 {
654 printk(banner);
655 return platform_driver_register(&s3c_rtc_driver);
656 }
657
658 static void __exit s3c_rtc_exit(void)
659 {
660 platform_driver_unregister(&s3c_rtc_driver);
661 }
662
663 module_init(s3c_rtc_init);
664 module_exit(s3c_rtc_exit);
665
666 MODULE_DESCRIPTION("Samsung S3C RTC Driver");
667 MODULE_AUTHOR("Ben Dooks <[email protected]>");
668 MODULE_LICENSE("GPL");
669 MODULE_ALIAS("platform:s3c2410-rtc");
里面的rtc_class_ops（就是字符驱动里file_operations的作用），完成了硬件的操作。如下：
static const struct rtc_class_ops s3c_rtcops = {
.open = s3c_rtc_open,
.release = s3c_rtc_release,
.read_time = s3c_rtc_gettime,
.set_time = s3c_rtc_settime,
.read_alarm = s3c_rtc_getalarm,
.set_alarm = s3c_rtc_setalarm,
.irq_set_freq = s3c_rtc_setfreq,
.irq_set_state = s3c_rtc_setpie,
.proc = s3c_rtc_proc,
.alarm_irq_enable = s3c_rtc_setaie,
};
再看probe函数，先从device里面获取资源，irq和mem，里面的函数以后慢慢再看啊！然后再使能rct，注册rtc_class_ops。后面是一些小操作。
这里的suspend和resume函数是电源管理的时候使用，这里先忽略。
remove函数，前面说了，就是字符设备里面的卸载，看看里面都有些什么吧。
platform_set_drvdata(dev, NULL); //将设备数据置0；
rtc_device_unregister(rtc); //注销rtc设备
s3c_rtc_setpie(&dev->dev, 0); //停止硬件中断
s3c_rtc_setaie(0);
clk_disable(rtc_clk); //rtc的一些注销
clk_put(rtc_clk);
rtc_clk = NULL;
iounmap(s3c_rtc_base); //释放内存空间
release_resource(s3c_rtc_mem);
kfree(s3c_rtc_mem);
注册和卸载的程序很简单。
static int __init s3c_rtc_init(void)
{
printk(banner);
return platform_driver_register(&s3c_rtc_driver);
}
static void __exit s3c_rtc_exit(void)
{
platform_driver_unregister(&s3c_rtc_driver);
}
至此，platform设备驱动粗略的讲述完毕。再次强调：它这样封装的好处，在设备和驱动分离，方便移植。当然，在同个平台，这样做很方便添加或删除外设驱动。 只需在板文件添加或注释掉就ok了。
ps：ioremap内核中的使用，往往是为某个设备预留一块内存，当使用的时候需要在board中定义这个设备的内存resource。通过 platform_get_resource获得设备的起始地址后，可以对其进行request_mem_region和ioremap等操作，以便应用程序对其进行操作。
时间： 2024-10-15 21:49:42