Linux下SPI总线驱动

1、Linux下SPI总线驱动有通用接口，一般的SPI设备驱动使用这个驱动接口实现设备驱动。分析驱动最好是先了解核心代码，然后从具体设备分析入手，然后从下至上，了解整个框架，再从上到下分析，理解透彻。以下分析内核根目录均以src代替。内核代码http:/lxr.linux.no/，版本。SPI的核心代码即src/drivers/spi/spi.cSPI 初始化和核心代码src/drivers/spi/spi_gpio.cIO模拟SPI接口代码头文件：src/include/linux/spi/spi.hsrc/include/linux/spi/spi_gpio.hsrc/incl

2、ude/linux/spi/spi_bitbang.h首先，先看核心代码。一步步来，先分析代码，然后看了具体驱动再回过头来看这个核心代码。spi.c- /* 这个函数是驱动模块卸载时使用 */ 32static void spidev_release(struct device *dev) 33 /* 标准设备结构体转换成SPI设备结构体 * 调用container_of函数获取dev设备所在的SPI设备结构体指针 */ 34 struct spi_device *spi = to_spi_device(dev); 35 36 /* spi masters may cleanup for re

3、leased devices */ /* 清空SPI主机申请的内存 */ 37 if (spi-master-cleanup) 38 spi-master-cleanup(spi); 39 /* 减调用次数 */ 40 spi_master_put(spi-master); /* 释放SPI设备节点内存 */ 41 kfree(spi); 42 43 /* 打印模块别名 */ 44static ssize_t 45modalias_show(struct device *dev, struct device_attribute *a, char *buf) 46 47 const struct

4、 spi_device *spi = to_spi_device(dev); 48 49 return sprintf(buf, %sn, spi-modalias); 50 51/* 设置SPI总线属性名称/显示 */ 52static struct device_attribute spi_dev_attrs = 53 _ATTR_RO(modalias), 54 _ATTR_NULL, 55;56 /* 获取设备ID */ 57/* modalias support makes modprobe $MODALIAS new-style hotplug work, 58 * and the

5、 sysfs version makes coldplug work too. 59 */ 60 61static const struct spi_device_id *spi_match_id(const struct spi_device_id *id, 62 const struct spi_device *sdev) 63 /* 判断设备中名称与模块别名相同，则返回该设备ID */ 64 while (id-name0) 65 if (!strcmp(sdev-modalias, id-name) 66 return id; 67 id+; 68 69 return NULL; 70

6、 71 /* 返回设备ID */ 72const struct spi_device_id *spi_get_device_id(const struct spi_device *sdev) 73 74 const struct spi_driver *sdrv = to_spi_driver(sdev-dev.driver); 75 76 return spi_match_id(sdrv-id_table, sdev); 77 78EXPORT_SYMBOL_GPL(spi_get_device_id);接上一个继续看spi.c。-匹配设备 /* 名词解释of: OpenFirmware *

7、 调用层次spi_match_device-of_driver_match_device-of_match_device- * of_match_node * 用于驱动程序检查platform_device是否在其支持列表里 */ 80static int spi_match_device(struct device *dev, struct device_driver *drv) 81 82 const struct spi_device *spi = to_spi_device(dev); 83 const struct spi_driver *sdrv = to_spi_driver(d

8、rv); 84 85 /* Attempt an OF style match */ /* 不匹配返回0；匹配返回非0，指向struct of_device_id类型的指针 * dev:需要查找的设备; drv:驱动程序结构体 */ 86 if (of_driver_match_device(dev, drv) 87 return 1; 88 /* 在驱动查找设备ID，找到返回真，否则假 */ 89 if (sdrv-id_table) 90 return !spi_match_id(sdrv-id_table, spi); 91 /* 比较设备别名和驱动名称，匹配返回真 */ 92 retu

9、rn strcmp(spi-modalias, drv-name) = 0; 93 94-uevent /* struct kobj_uevent_env 是内核用户空间的一个环境参数 * uevent是sysfs向用户空间发出的消息，这里实际上添加的是一串字符串消息。 * 关于uevent参考:/walkingman321/archive/2010/10/01/.aspx */ 95static int spi_uevent(struct device *dev, struct kobj_uevent_env *env) 96 97 const stru

10、ct spi_device *spi = to_spi_device(dev); 98 99 add_uevent_var(env, MODALIAS=%s%s, SPI_MODULE_PREFIX, spi-modalias); 100 return 0; 101-电源管理 /* 配置了电源管理 * 现在不清楚suspend和resume函数哪里实现，等找到了再说 */ 103#ifdef CONFIG_PM 104 /* 挂起 */ 105static int spi_suspend(struct device *dev, pm_message_t message) 106 107 int

11、 value = 0; 108 struct spi_driver *drv = to_spi_driver(dev-driver); 109 110 /* suspend will stop irqs and dma; no more i/o */ /* 挂起将定制终端和DMA，没有输入输出 */ 111 if (drv) /* 驱动实现了挂起操作函数 */ 112 if (drv-suspend) 113 value = drv-suspend(to_spi_device(dev), message); 114 else 115 dev_dbg(dev, . cant suspendn);

12、 116 117 return value; 118 119 /* 恢复 */ 120static int spi_resume(struct device *dev) 121 122 int value = 0; 123 struct spi_driver *drv = to_spi_driver(dev-driver); 124 125 /* resume may restart the i/o queue */ /* 重新开始输入输出队列 */ 126 if (drv) 127 if (drv-resume) 128 value = drv-resume(to_spi_device(de

13、v); 129 else 130 dev_dbg(dev, . cant resumen); 131 132 return value; 133 134 135#else /* 没有电源管理 */ 136#define spi_suspend NULL 137#define spi_resume NULL 138#endif-总线 /* 总线 参考:/xingzuzi/blog/item/d12c03f473b3c2a0a50f5260.html */ 140struct bus_type spi_bus_type = 141 .name = spi, 14

14、2 .dev_attrs = spi_dev_attrs, 143 .match = spi_match_device, 144 .uevent = spi_uevent, 145 .suspend = spi_suspend, 146 .resume = spi_resume, 147; 148EXPORT_SYMBOL_GPL(spi_bus_type);-驱动注册、删除/* 驱动注册 */ 151static int spi_drv_probe(struct device *dev) 152 153 const struct spi_driver *sdrv = to_spi_drive

15、r(dev-driver); 154 155 return sdrv-probe(to_spi_device(dev); 156 157 /* 驱动删除 */ 158static int spi_drv_remove(struct device *dev) 159 160 const struct spi_driver *sdrv = to_spi_driver(dev-driver); 161 162 return sdrv-remove(to_spi_device(dev); 163 164 /* 关闭 */ 165static void spi_drv_shutdown(struct d

16、evice *dev) 166 167 const struct spi_driver *sdrv = to_spi_driver(dev-driver); 168 169 sdrv-shutdown(to_spi_device(dev); 170-注册SPI总线驱动 /* 注册SPI驱动 */ 172/* 173 * spi_register_driver - register a SPI driver 174 * sdrv: the driver to register 175 * Context: can sleep 176 */ 177int spi_register_driver(s

17、truct spi_driver *sdrv) 178 /* 初始化总线结构体 */ 179 sdrv-driver.bus = &spi_bus_type; /* 初始化驱动相关函数 */ 180 if (sdrv-probe) 181 be = spi_drv_probe; 182 if (sdrv-remove) 183 sdrv-driver.remove = spi_drv_remove; 184 if (sdrv-shutdown) 185 sdrv-driver.shutdown = spi_drv_shutdown; /* 驱动注册 * 添加驱动到

18、总线 * sysfs、uevent等创建、初始化 */ 186 return driver_register(&sdrv-driver); 187 188EXPORT_SYMBOL_GPL(spi_register_driver);接下去看spi.c特殊的板级相关设备添加方法 /* 神奇的分割线 */ 190/*-*/ 191 192/* SPI devices should normally not be created by SPI device drivers; that 193 * would make them board-specific. Similarly with SPI m

19、aster drivers. 194 * Device registration normally goes into like arch/./mach./board-YYY.c 195 * with other readonly (flashable) information about mainboard devices. 196 */ 197 /* 板级相关信息链表 */ 198struct boardinfo 199 struct list_head list; 200 struct spi_board_info board_info; 201; 202 203static LIST_

20、HEAD(board_list); 204static LIST_HEAD(spi_master_list); 206/* 207 * Used to protect add/del opertion for board_info list and 208 * spi_master list, and their matching process 209 */ /* 链表操作锁 */ 210static DEFINE_MUTEX(board_lock); 211 212/* 213 * spi_alloc_device - Allocate a new SPI device 214 * mas

21、ter: Controller to which device is connected 215 * Context: can sleep 216 * 217 * Allows a driver to allocate and initialize a spi_device without 218 * registering it immediately. This allows a driver to directly 219 * fill the spi_device with device parameters before calling 220 * spi_add_device()

22、on it. 221 * 222 * Caller is responsible to call spi_add_device() on the returned 223 * spi_device structure to add it to the SPI master. If the caller 224 * needs to discard the spi_device without adding it, then it should 225 * call spi_dev_put() on it. 226 * 227 * Returns a pointer to the new dev

23、ice, or NULL. 228 */ /* 为申请SPI设备结构体空间而不注册设备，必须调用spi_add_device，如要丢弃这个设备 * 则必须调用spi_dev_put */ 229struct spi_device *spi_alloc_device(struct spi_master *master) 230 231 struct spi_device *spi; 232 struct device *dev = master-dev.parent; 233 /* 增加设备引用次数，相反操作spi_master_put */ 234 if (!spi_master_get(ma

24、ster) 235 return NULL; 236 /* 申请内核空间内存 */ 237 spi = kzalloc(sizeof *spi, GFP_KERNEL); 238 if (!spi) 239 dev_err(dev, cannot alloc spi_devicen); 240 spi_master_put(master); 241 return NULL; 242 243 /* SPI主机控制结构体 */ 244 spi-master = master; /* 设备 */ 245 spi-dev.parent = dev; /* 总线 */ 246 spi-dev.bus =

25、 &spi_bus_type; /* 删除方法 */ 247 spi-dev.release = spidev_release; /* 设备初始化 * 初始化kobject，dma池链表，设备互斥锁，自旋锁，设备对象的电源相关部分 * src/drivers/base/core.c */ 248 device_initialize(&spi-dev); /* 返回spi设备结构体指针 */ 249 return spi; 250 251EXPORT_SYMBOL_GPL(spi_alloc_device); 252 253/* 254 * spi_add_device - Add spi_de

26、vice allocated with spi_alloc_device 255 * spi: spi_device to register 256 * 257 * Companion function to spi_alloc_device. Devices allocated with 258 * spi_alloc_device can be added onto the spi bus with this function. 259 * 260 * Returns 0 on success; negative errno on failure 261 */ /* 与spi_alloc_

27、device配合使用，将设备结构体添加到SPI总线 */ 262int spi_add_device(struct spi_device *spi) 263 264 static DEFINE_MUTEX(spi_add_lock); 265 struct device *dev = spi-master-dev.parent; 266 struct device *d; 267 int status; 268 269 /* Chipselects are numbered 0.max; validate. */ /* 设备片选编号比SPI主控制器的片选大，出错 */ 270 if (spi-

28、chip_select = spi-master-num_chipselect) 271 dev_err(dev, cs%d = max %dn, 272 spi-chip_select, 273 spi-master-num_chipselect); 274 return -EINVAL; 275 276 277 /* Set the bus ID string */ /* 设置设备名称，调用kobject的设置设备名称参数方法 */ 278 dev_set_name(&spi-dev, %s.%u, dev_name(&spi-master-dev), 279 spi-chip_selec

29、t); 280 281 282 /* We need to make sure theres no other device with this 283 * chipselect *BEFORE* we call setup(), else well trash 284 * its configuration. Lock against concurrent add() calls. 285 */ /* 互斥锁，保证设置时，没有其他设备用这个片选，防止并发添加add() */ 286 mutex_lock(&spi_add_lock); 287 /* 按照名称字符查找设备结构体，设备名称由de

30、v_name查找kobject返回 * 能够找到说明设备已经在用 */ 288 d = bus_find_device_by_name(&spi_bus_type, NULL, dev_name(&spi-dev); 289 if (d != NULL) 290 dev_err(dev, chipselect %d already in usen, 291 spi-chip_select); 292 put_device(d); 293 status = -EBUSY; 294 goto done; 295 296 297 /* Drivers may modify this initial

31、i/o setup, but will 298 * normally rely on the device being setup. Devices 299 * using SPI_CS_HIGH cant coexist well otherwise. 300 */ /* /* 设置SPI模式和时钟频率 * 驱动可以初始化IO，当设备被设置的时候 * 取消片选没有用 * 详细见后面驱动核心方法spi_setup解析 */ 301 status = spi_setup(spi); 302 if (status dev), status); 305 goto done; 306 307 308

32、/* Device may be bound to an active driver when this returns */ /* 将设备添加到驱动层次结构，添加到kobject层次结构，添加到其他子系统 */ 309 status = device_add(&spi-dev); 310 if (status dev), status); 313 else 314 dev_dbg(dev, registered child %sn, dev_name(&spi-dev); 315 316done: 317 mutex_unlock(&spi_add_lock); 318 return sta

33、tus; 319 320EXPORT_SYMBOL_GPL(spi_add_device); 321 322/* 323 * spi_new_device - instantiate one new SPI device 324 * master: Controller to which device is connected 325 * chip: Describes the SPI device 326 * Context: can sleep 327 * 328 * On typical mainboards, this is purely internal; and its not n

34、eeded 329 * after board init creates the hard-wired devices. Some development 330 * platforms may not be able to use spi_register_board_info though, and 331 * this is exported so that for example a USB or parport based adapter 332 * driver could add devices (which it would learn about out-of-band).

35、333 * 334 * Returns the new device, or NULL. 335 */ /* 有些开发平台可能不能通过spi_register_board_info添加设备 * 这个用来让一些比如基于USB适配的驱动添加设备 */ 336struct spi_device *spi_new_device(struct spi_master *master, 337 struct spi_board_info *chip) 338 339 struct spi_device *proxy; 340 int status; 341 342 /* NOTE: caller did a

36、ny chip-bus_num checks necessary. 343 * 344 * Also, unless we change the return value convention to use 345 * error-or-pointer (not NULL-or-pointer), troubleshootability 346 * suggests syslogged diagnostics are best here (ugh). 347 */ 348 /* 分配设备结构体内存空间，并初始化 */ 349 proxy = spi_alloc_device(master);

37、350 if (!proxy) 351 return NULL; 352 353 WARN_ON(strlen(chip-modalias) = sizeof(proxy-modalias); 354 355 proxy-chip_select = chip-chip_select; 356 proxy-max_speed_hz = chip-max_speed_hz; 357 proxy-mode = chip-mode; 358 proxy-irq = chip-irq; 359 strlcpy(proxy-modalias, chip-modalias, sizeof(proxy-mod

38、alias); 360 proxy-dev.platform_data = (void *) chip-platform_data; 361 proxy-controller_data = chip-controller_data; 362 proxy-controller_state = NULL; 363 /* 添加设备 */ 364 status = spi_add_device(proxy); 365 if (status bus_num != bi-bus_num) 380 return; 381 382 dev = spi_new_device(master, bi); 383 i

39、f (!dev) 384 dev_err(master-dev.parent, cant create new device for %sn, 385 bi-modalias); 386 387 388/* 389 * spi_register_board_info - register SPI devices for a given board 390 * info: array of chip descriptors 391 * n: how many descriptors are provided 392 * Context: can sleep 393 * 394 * Board-s

40、pecific early init code calls this (probably during arch_initcall) 395 * with segments of the SPI device table. Any device nodes are created later, 396 * after the relevant parent SPI controller (bus_num) is defined. We keep 397 * this table of devices forever, so that reloading a controller driver

41、will 398 * not make Linux forget about these hard-wired devices. 399 * 400 * Other code can also call this, e.g. a particular add-on board might provide 401 * SPI devices through its expansion connector, so code initializing that board 402 * would naturally declare its SPI devices. 403 * 404 * The b

42、oard info passed can safely be _initdata . but be careful of 405 * any embedded pointers (platform_data, etc), theyre copied as-is. 406 */ /* 使用一系列板级描述信息初始化设备 */ 407int _init 408spi_register_board_info(struct spi_board_info const *info, unsigned n) 409 410 struct boardinfo *bi; 411 int i; 412 413 bi

43、 = kzalloc(n * sizeof(*bi), GFP_KERNEL); 414 if (!bi) 415 return -ENOMEM; 416 417 for (i = 0; i board_info, info, sizeof(*info); 421 mutex_lock(&board_lock); /* 添加到板级描述符链表 */ 422 list_add_tail(&bi-list, &board_list); /* 将主机控制类链表所有的节点匹配板级信息的设备初始化 */ 423 list_for_each_entry(master, &spi_master_list, list) 424 spi_match_master_to_boardinfo(master, &bi-board_info); 425 mutex_unlock(&board_lock); 4