linux spi裝置驅動中probe函式何時被呼叫
阿新 • • 發佈：2019-01-04
這兩天被裝置檔案快搞瘋了，也怪自己學東西一知半解吧，弄了幾天總算能把設備註冊理清楚一點點了。就以spi子裝置的註冊為例總結一下，免得自己忘記。
首先以註冊一個spidev的裝置為例:
static struct spi_board_info imx5_spi_printer_device[] __initdata =
{
{
.modalias = "spidev",
.max_speed_hz = 8000000,
.bus_num = 1,
.chip_select = 1,
.mode = SPI_MODE_0,
},
};spi_register_board_info(imx5_spi_printer_device,ARRAY_SIZE(imx5_spi_printer_device));
在mx5_loco.c檔案中新增上面結構體spi_board_info，modalias必須指定已有的一個驅動，至於bus_num和chip_select,如果你不知道bus_num是多少，可以在你的父驅動中打印出來，這裡的bus_num一定要和父類的bus_num一致，否則是無法生成裝置檔案的。如果spi一直沒有時鐘訊號，很有可能是bus_num不對。
這樣系統起來之後就會在/dev目錄下出現一個名為spidev1.1的裝置檔案，讀寫這個檔案就可以實現spi的操作
還有下面這種情況：
static struct spi_board_info prt_spi_device[] __initdata = { { .modalias = "HotPRT", .max_speed_hz = 12500000, /* max spi clock (SCK) speed in HZ */ .bus_num = 1, .chip_select = 1, // .mode = SPI_MODE_0, .platform_data = 0, }, };
spi_register_board_info(prt_spi_device, ARRAY_SIZE(prt_spi_device));
我自己實現了一個spi的驅動，然後需要建立一個裝置檔案，裝置檔案的建立是在probe中完成。
但是我開始一直觸發不了probe，於是找啊找，總算知道probe的呼叫過程了，如下:static struct spi_driver prt_driver = { .driver = { .name = "HotPRT", .bus = &spi_bus_type, .owner = THIS_MODULE, }, .probe = prt_probe, .remove = __devexit_p(prt_remove), }; spi_register_driver(&prt_driver);
int spi_register_driver(struct spi_driver *sdrv)
{
sdrv->driver.bus = &spi_bus_type;
if (sdrv->probe)
sdrv->driver.probe = spi_drv_probe;
if (sdrv->remove)
sdrv->driver.remove = spi_drv_remove;
if (sdrv->shutdown)
sdrv->driver.shutdown = spi_drv_shutdown;
return driver_register(&sdrv->driver);
}然後呼叫driver_register
<pre name="code" class="cpp">int driver_register(struct device_driver *drv)
{
int ret;
struct device_driver *other;
BUG_ON(!drv->bus->p);
if ((drv->bus->probe && drv->probe) ||
(drv->bus->remove && drv->remove) ||
(drv->bus->shutdown && drv->shutdown))
printk(KERN_WARNING "Driver '%s' needs updating - please use "
"bus_type methods\n", drv->name);
other = driver_find(drv->name, drv->bus);
if (other) {
put_driver(other);
printk(KERN_ERR "Error: Driver '%s' is already registered, "
"aborting...\n", drv->name);
return -EBUSY;
}
ret = bus_add_driver(drv);
if (ret)
return ret;
ret = driver_add_groups(drv, drv->groups);
if (ret)
bus_remove_driver(drv);
return ret;
}直接看bus_add_driver
klist_init(&priv->klist_devices, NULL, NULL);
priv->driver = drv;
drv->p = priv;
priv->kobj.kset = bus->p->drivers_kset;
error = kobject_init_and_add(&priv->kobj, &driver_ktype, NULL,
"%s", drv->name);
if (error)
goto out_unregister;
if (drv->bus->p->drivers_autoprobe) {
error = driver_attach(drv);
if (error)
goto out_unregister;
}
klist_add_tail(&priv->knode_bus, &bus->p->klist_drivers);
module_add_driver(drv->owner, drv);這裡只擷取一部分，最後呼叫的是driver_attach
int driver_attach(struct device_driver * drv)
{
return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
}真正起作用的是__driver_attach：
static int __driver_attach(struct device * dev, void * data)
{
。。。
if (!dev->driver)
driver_probe_device(drv, dev);
。。。
}int driver_probe_device(struct device_driver * drv, struct device * dev)
{
。。。
//1.先是判斷bus是否match：
if (drv->bus->match && !drv->bus->match(dev, drv))
goto done;
//2.再具體執行probe：
ret = really_probe(dev, drv);
。。。
}
really_probe才是我們要找的函式：
static int really_probe(struct device *dev, struct device_driver *drv)
{
。。。
//1.先是呼叫的驅動所屬匯流排的probe函式：
if (dev->bus->probe) {
ret = dev->bus->probe(dev);
if (ret)
goto probe_failed;
} else if (drv->probe) {
//2.再呼叫你的驅動中的probe函式：
ret = drv->probe(dev);
if (ret)
goto probe_failed;
}
。。。
}其中，drv->probe(dev)，才是真正呼叫你的驅動實現的具體的probe函式。至此probe函式被呼叫。
在板檔案中新增spi_board_info，並在板檔案的init函式中呼叫spi_register_board_info(
prt_spi_device<span style="font-family: NSimSum; line-height: 1.5; ">,ARRAY_SIZE(</span><span style="font-family: NSimSum; ">prt_spi_device</span><span style="font-family: Verdana, Geneva, Arial, Helvetica, sans-serif; line-height: 1.5; "><span style="line-height: 1.5; font-family: NSimSum; ">))</span></span><span style="font-family: Verdana, Geneva, Arial, Helvetica, sans-serif; line-height: 1.5; ">;</span>//註冊spi_board_info。這個程式碼會把spi_board_info註冊到連結串列board_list上。spi_device封裝了一個spi_master結構體，事實上spi_master的註冊會在spi_register_board_info之後，spi_master註冊的過程中會呼叫scan_boardinfo掃描board_list，找到掛接在它上面的spi裝置，然後建立並註冊spi_device。
另外有關spi片選引腳的設定：1、直接將gpio配置成spi片選功能引腳。 2、將gpio配置成片選引腳，這個時候就需要設定結構體
static void mx53_loco_gpio_spi_chipselect_active(int cspi_mode, int status,
int chipselect)
{
switch (cspi_mode) {
case 1: //ESPI1,bus_num 1
switch (chipselect) {
case 0x1://SS0 chipselect = .chip_select + 1
{
iomux_v3_cfg_t cspi_ss0 = MX53_PAD_CSI0_DAT7__ECSPI1_SS0;
iomux_v3_cfg_t cspi_ss2 = MX53_PAD_KEY_ROW2__GPIO4_11;//SS2
mxc_iomux_v3_setup_pad(cspi_ss0);
mxc_iomux_v3_setup_pad(cspi_ss2);
gpio_request(ECSPI1_CS2, "ecspi-cs2");
gpio_direction_input(ECSPI1_CS2);
}
break;
default:
break;
}
case 2://ESPI2,bus_num 2
switch (chipselect) {
case 0x2://SS0
{
gpio_request(ECSPI2_SS1, "ecspi-cs1");
gpio_direction_output(ECSPI2_SS1, 1);
}
break;
case 0x3://SS1
{
gpio_request(ECSPI2_SS1, "ecspi-cs1");
gpio_direction_output(ECSPI2_SS1, 0);
}
break;
default:
break;
}
default:
break;
}
}
static void mx53_loco_gpio_spi_chipselect_inactive(int cspi_mode, int status,
int chipselect)
{
switch (cspi_mode) {
case 1:
switch (chipselect) {
case 0x1:
gpio_free(ECSPI1_CS2);
break;
default:
break;
}
case 2:
switch (chipselect) {
case 0x2:
{
gpio_request(ECSPI2_SS1, "ecspi-cs1");
gpio_direction_output(ECSPI2_SS1, 0);
}
break;
case 0x3:
{
gpio_request(ECSPI2_SS1, "ecspi-cs1");
gpio_direction_output(ECSPI2_SS1, 1);
}
break;
default:
break;
}
default:
break;
}
}
static struct mxc_spi_master mxcspi_data = {
.maxchipselect = 4,
.spi_version = 23,
.chipselect_active = mx53_loco_gpio_spi_chipselect_active,
.chipselect_inactive = mx53_loco_gpio_spi_chipselect_inactive,
};裝置檔案的生成：
1、用mknod手動生成
通過cat /proc/devices命令，可以看到主裝置的編號，例如spi是153 ，如果想生成一個spi的子裝置可以用 mknod /dev/spidev -c 153 1
mknod 裝置名 裝置型別 主裝置號 子裝置號
2、在驅動中就加入建立裝置檔案的程式碼：
struct device *devi;
prt_class = class_create(THIS_MODULE, PRT_DEV_NAME);
if(IS_ERR(prt_class))
PTR_ERR(prt_class);
devi = device_create(prt_class,NULL,MKDEV(PRT_DEV_MAJOR, 1), NULL, PRT_DEV_NAME);
if(IS_ERR(devi))
PTR_ERR(devi);