Linux驱动修炼之道-SPI驱动框架源码分析(中)
2011-12-29 21:16
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努力成为linux kernel hacker的人李万鹏原创作品,为梦而战。转载请标明出处
http://blog.csdn.net/woshixingaaa/archive/2011/06/29/6574220.aspx
这篇来分析spi子系统的建立过程。
嵌入式微处理器访问SPI设备有两种方式:使用GPIO模拟SPI接口的工作时序或者使用SPI控制器。使用GPIO模拟SPI接口的工作时序是非常容易实现的,但是会导致大量的时间耗费在模拟SPI接口的时序上,访问效率比较低,容易成为系统瓶颈。这里主要分析使用SPI控制器的情况。
这个是由sys文件系统导出的spi子系统在内核中的视图了。
首先了解一下Linux内核中的几个文件:spi.c也就是spi子系统的核心了,spi_s3c24xx.c是s3c24xx系列芯片的SPI controller驱动,它向更上层的SPI核心层(spi.c)提供接口用来控制芯片的SPI controller,是一个被其他驱动使用的驱动。而spidev.c是在核心层基础之上将SPI controller模拟成一个字符型的驱动,向文件系统提供标准的文件系统接口,用来操作对应的SPI
controller。
下面我们来看看spi子系统是怎么注册进内核的:
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static int __init spi_init(void)
{
int status;
buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
if (!buf) {
status = -ENOMEM;
goto err0;
}
status = bus_register(&spi_bus_type);
if (status < 0)
goto err1;
status = class_register(&spi_master_class);
if (status < 0)
goto err2;
return 0;
err2:
bus_unregister(&spi_bus_type);
err1:
kfree(buf);
buf = NULL;
err0:
return status;
}
postcore_initcall(spi_init);
controller的0号接口,s3c24xx-spi.1表示s3c2440的spi controller的1号接口。注册了s3c24xx_spi_driver后,赋值了平台驱动的probe函数为s3c24xx_spi_probe。所以当match成功后,调用s3c24xx_spi_probe,这里看其实现:
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static int __init s3c24xx_spi_probe(struct platform_device *pdev)
{
struct s3c2410_spi_info *pdata;
struct s3c24xx_spi *hw;
struct spi_master *master;
struct resource *res;
int err = 0;
/*分配struct spi_master+struct s3c24xx_spi大小的数据,把s3c24xx_spi设为spi_master的私有数据*/
master = spi_alloc_master(&pdev->dev, sizeof(struct s3c24xx_spi));
if (master == NULL) {
dev_err(&pdev->dev, "No memory for spi_master\n");
err = -ENOMEM;
goto err_nomem;
}
/*从master中获得s3c24xx_spi*/
hw = spi_master_get_devdata(master);
memset(hw, 0, sizeof(struct s3c24xx_spi));
hw->master = spi_master_get(master);
/*驱动移植的时候需要实现的重要结构,初始化为&s3c2410_spi0_platdata*/
hw->pdatapdata = pdata = pdev->dev.platform_data;
hw->dev = &pdev->dev;
if (pdata == NULL) {
dev_err(&pdev->dev, "No platform data supplied\n");
err = -ENOENT;
goto err_no_pdata;
}
/*设置平台的私有数据为s3c24xx_spi*/
platform_set_drvdata(pdev, hw);
init_completion(&hw->done);
/* setup the master state. */
/*该总线上的设备数*/
master->num_chipselect = hw->pdata->num_cs;
/*总线号*/
master->bus_num = pdata->bus_num;
/* setup the state for the bitbang driver */
/*spi_bitbang专门负责数据的传输*/
hw->bitbang.master = hw->master;
hw->bitbang.setup_transfer = s3c24xx_spi_setupxfer;
hw->bitbang.chipselect = s3c24xx_spi_chipsel;
hw->bitbang.txrx_bufs = s3c24xx_spi_txrx;
hw->bitbang.master->setup = s3c24xx_spi_setup;
dev_dbg(hw->dev, "bitbang at %p\n", &hw->bitbang);
。。。。。。。。。。。。。。。。。。。。。。。。
/*初始化设置寄存器,包括对SPIMOSI,SPIMISO,SPICLK引脚的设置*/
s3c24xx_spi_initialsetup(hw);
/* register our spi controller */
err = spi_bitbang_start(&hw->bitbang);
。。。。。。。。。。。。。。。。。。。。。
}
然后看这里是怎样注册spi主机控制器驱动的:
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int spi_register_master(struct spi_master *master)
{
。。。。。。。。。。。。。。。。
/*将spi添加到内核,这也是sys/class/Spi_master下产生Spi0,Spi1的原因*/
dev_set_name(&master->dev, "spi%u", master->bus_num);
status = device_add(&master->dev);
scan_boardinfo(master);
}
这个函数完成了将spi_board_info交由boardinfo管理,并把boardinfo挂载到board_list链表上。也就是说在系统初始化的时候将spi_device交由到挂在board_list上的boardinfo管理,在spi controller的driver注册的时候不但注册这个主机控制器的驱动,还要遍历这个主机控制器的总线上的spi_device,将总线上的spi_device全部注册进内核。当注册进内核并且spi_driver已经注册的时候,如果总线match成功,则会调用spi_driver的probe函数,这个将在后边进行分析。
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int __init
spi_register_board_info(struct spi_board_info const *info, unsigned n)
{
struct boardinfo *bi;
bi = kmalloc(sizeof(*bi) + n * sizeof *info, GFP_KERNEL);
if (!bi)
return -ENOMEM;
bi->nn_board_info = n;
memcpy(bi->board_info, info, n * sizeof *info);
mutex_lock(&board_lock);
list_add_tail(&bi->list, &board_list);
mutex_unlock(&board_lock);
return 0;
}
下面来看分配spi_alloc_device的函数,主要完成了分配spi_device,并初始化spi->dev的一些字段。
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struct spi_device *spi_alloc_device(struct spi_master *master)
{
struct spi_device *spi;
struct device *dev = master->dev.parent;
if (!spi_master_get(master))
return NULL;
spi = kzalloc(sizeof *spi, GFP_KERNEL);
if (!spi) {
dev_err(dev, "cannot alloc spi_device\n");
spi_master_put(master);
return NULL;
}
spi->master = master;
spi->dev.parent = dev;
/*设置总线是spi_bus_type,下面会讲到spi_device与spi_driver是怎样match上的*/
spi->dev.bus = &spi_bus_type;
spi->dev.release = spidev_release;
device_initialize(&spi->dev);
return spi;
}
在spidev.c中:
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static int __init spidev_init(void)
{
int status;
BUILD_BUG_ON(N_SPI_MINORS > 256);
status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
if (status < 0)
return status;
spidev_class = class_create(THIS_MODULE, "spidev");
if (IS_ERR(spidev_class)) {
unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
return PTR_ERR(spidev_class);
}
status = spi_register_driver(&spidev_spi);
if (status < 0) {
class_destroy(spidev_class);
unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
}
return status;
}
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static struct spi_driver spidev_spi = {
.driver = {
.name = "spidev",
.owner = THIS_MODULE,
},
.probe = spidev_probe,
.remove = __devexit_p(spidev_remove),
};
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struct bus_type spi_bus_type = {
.name = "spi",
.dev_attrs = spi_dev_attrs,
.match = spi_match_device,
.uevent = spi_uevent,
.suspend = spi_suspend,
.resume = spi_resume,
};
static int spi_match_device(struct device *dev, struct device_driver *drv)
{
const struct spi_device *spi = to_spi_device(dev);
return strcmp(spi->modalias, drv->name) == 0;
}
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static int spidev_remove(struct spi_device *spi)
{
struct spidev_data *spidev = spi_get_drvdata(spi);
/* make sure ops on existing fds can abort cleanly */
spin_lock_irq(&spidev->spi_lock);
spidev->spi = NULL;
spi_set_drvdata(spi, NULL);
spin_unlock_irq(&spidev->spi_lock);
/* prevent new opens */
mutex_lock(&device_list_lock);
list_del(&spidev->device_entry);
device_destroy(spidev_class, spidev->devt);
clear_bit(MINOR(spidev->devt), minors);
if (spidev->users == 0)
kfree(spidev);
mutex_unlock(&device_list_lock);
return 0;
}
来源:http://blog.csdn.net/woshixingaaa/article/details/6574220
http://blog.csdn.net/woshixingaaa/archive/2011/06/29/6574220.aspx
这篇来分析spi子系统的建立过程。
嵌入式微处理器访问SPI设备有两种方式:使用GPIO模拟SPI接口的工作时序或者使用SPI控制器。使用GPIO模拟SPI接口的工作时序是非常容易实现的,但是会导致大量的时间耗费在模拟SPI接口的时序上,访问效率比较低,容易成为系统瓶颈。这里主要分析使用SPI控制器的情况。
这个是由sys文件系统导出的spi子系统在内核中的视图了。
首先了解一下Linux内核中的几个文件:spi.c也就是spi子系统的核心了,spi_s3c24xx.c是s3c24xx系列芯片的SPI controller驱动,它向更上层的SPI核心层(spi.c)提供接口用来控制芯片的SPI controller,是一个被其他驱动使用的驱动。而spidev.c是在核心层基础之上将SPI controller模拟成一个字符型的驱动,向文件系统提供标准的文件系统接口,用来操作对应的SPI
controller。
下面我们来看看spi子系统是怎么注册进内核的:
view plaincopy
to clipboardprint?
static int __init spi_init(void)
{
int status;
buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
if (!buf) {
status = -ENOMEM;
goto err0;
}
status = bus_register(&spi_bus_type);
if (status < 0)
goto err1;
status = class_register(&spi_master_class);
if (status < 0)
goto err2;
return 0;
err2:
bus_unregister(&spi_bus_type);
err1:
kfree(buf);
buf = NULL;
err0:
return status;
}
postcore_initcall(spi_init);
view plaincopy to clipboardprint? static int __init s3c24xx_spi_init(void) { return platform_driver_probe(&s3c24xx_spi_driver, s3c24xx_spi_probe); } static int __init s3c24xx_spi_init(void) { return platform_driver_probe(&s3c24xx_spi_driver, s3c24xx_spi_probe); }platform_driver_probe中完成了s3c24xx_spi_driver这个平台驱动的注册,相应的平台设备在devs.c中定义,在smdk2440_devices中添加&s3c_device_spi0,&s3c_device_spi1,这就生成了图中所示的s3c24xx-spi.0与s3c24xx-spi.1,当然了这图是在网上找的,不是我画的,所以是6410的。这里s3c24xx-spi.0表示s3c2440的spi
controller的0号接口,s3c24xx-spi.1表示s3c2440的spi controller的1号接口。注册了s3c24xx_spi_driver后,赋值了平台驱动的probe函数为s3c24xx_spi_probe。所以当match成功后,调用s3c24xx_spi_probe,这里看其实现:
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static int __init s3c24xx_spi_probe(struct platform_device *pdev)
{
struct s3c2410_spi_info *pdata;
struct s3c24xx_spi *hw;
struct spi_master *master;
struct resource *res;
int err = 0;
/*分配struct spi_master+struct s3c24xx_spi大小的数据,把s3c24xx_spi设为spi_master的私有数据*/
master = spi_alloc_master(&pdev->dev, sizeof(struct s3c24xx_spi));
if (master == NULL) {
dev_err(&pdev->dev, "No memory for spi_master\n");
err = -ENOMEM;
goto err_nomem;
}
/*从master中获得s3c24xx_spi*/
hw = spi_master_get_devdata(master);
memset(hw, 0, sizeof(struct s3c24xx_spi));
hw->master = spi_master_get(master);
/*驱动移植的时候需要实现的重要结构,初始化为&s3c2410_spi0_platdata*/
hw->pdatapdata = pdata = pdev->dev.platform_data;
hw->dev = &pdev->dev;
if (pdata == NULL) {
dev_err(&pdev->dev, "No platform data supplied\n");
err = -ENOENT;
goto err_no_pdata;
}
/*设置平台的私有数据为s3c24xx_spi*/
platform_set_drvdata(pdev, hw);
init_completion(&hw->done);
/* setup the master state. */
/*该总线上的设备数*/
master->num_chipselect = hw->pdata->num_cs;
/*总线号*/
master->bus_num = pdata->bus_num;
/* setup the state for the bitbang driver */
/*spi_bitbang专门负责数据的传输*/
hw->bitbang.master = hw->master;
hw->bitbang.setup_transfer = s3c24xx_spi_setupxfer;
hw->bitbang.chipselect = s3c24xx_spi_chipsel;
hw->bitbang.txrx_bufs = s3c24xx_spi_txrx;
hw->bitbang.master->setup = s3c24xx_spi_setup;
dev_dbg(hw->dev, "bitbang at %p\n", &hw->bitbang);
。。。。。。。。。。。。。。。。。。。。。。。。
/*初始化设置寄存器,包括对SPIMOSI,SPIMISO,SPICLK引脚的设置*/
s3c24xx_spi_initialsetup(hw);
/* register our spi controller */
err = spi_bitbang_start(&hw->bitbang);
。。。。。。。。。。。。。。。。。。。。。
}
view plaincopy to clipboardprint? int spi_bitbang_start(struct spi_bitbang *bitbang) { int status; if (!bitbang->master || !bitbang->chipselect) return -EINVAL; /*动态创建一个work_struct结构,它的处理函数是bitbang_work*/ INIT_WORK(&bitbang->work, bitbang_work); spin_lock_init(&bitbang->lock); INIT_LIST_HEAD(&bitbang->queue); /*spi的数据传输就是用这个方法*/ if (!bitbang->master->transfer) bitbang->master->transfer = spi_bitbang_transfer; if (!bitbang->txrx_bufs) { bitbang->use_dma = 0; /*spi_s3c24xx.c中有spi_bitbang_bufs方法,在bitbang_work中被调用*/ bitbang->txrx_bufs = spi_bitbang_bufs; if (!bitbang->master->setup) { if (!bitbang->setup_transfer) bitbang->setup_transfer = spi_bitbang_setup_transfer; /*在spi_s3c24xx.c中有setup的处理方法,在spi_new_device中被调用*/ bitbang->master->setup = spi_bitbang_setup; bitbang->master->cleanup = spi_bitbang_cleanup; } } else if (!bitbang->master->setup) return -EINVAL; /* this task is the only thing to touch the SPI bits */ bitbang->busy = 0; /调用create_singlethread_workqueue创建单个工作线程/ bitbang->workqueue = create_singlethread_workqueue( dev_name(bitbang->master->dev.parent)); if (bitbang->workqueue == NULL) { status = -EBUSY; goto err1; } status = spi_register_master(bitbang->master); if (status < 0) goto err2; return status; err2: destroy_workqueue(bitbang->workqueue); err1: return status; } int spi_bitbang_start(struct spi_bitbang *bitbang) { int status; if (!bitbang->master || !bitbang->chipselect) return -EINVAL; /*动态创建一个work_struct结构,它的处理函数是bitbang_work*/ INIT_WORK(&bitbang->work, bitbang_work); spin_lock_init(&bitbang->lock); INIT_LIST_HEAD(&bitbang->queue); /*spi的数据传输就是用这个方法*/ if (!bitbang->master->transfer) bitbang->master->transfer = spi_bitbang_transfer; if (!bitbang->txrx_bufs) { bitbang->use_dma = 0; /*spi_s3c24xx.c中有spi_bitbang_bufs方法,在bitbang_work中被调用*/ bitbang->txrx_bufs = spi_bitbang_bufs; if (!bitbang->master->setup) { if (!bitbang->setup_transfer) bitbang->setup_transfer = spi_bitbang_setup_transfer; /*在spi_s3c24xx.c中有setup的处理方法,在spi_new_device中被调用*/ bitbang->master->setup = spi_bitbang_setup; bitbang->master->cleanup = spi_bitbang_cleanup; } } else if (!bitbang->master->setup) return -EINVAL; /* this task is the only thing to touch the SPI bits */ bitbang->busy = 0; /调用create_singlethread_workqueue创建单个工作线程/ bitbang->workqueue = create_singlethread_workqueue( dev_name(bitbang->master->dev.parent)); if (bitbang->workqueue == NULL) { status = -EBUSY; goto err1; } status = spi_register_master(bitbang->master); if (status < 0) goto err2; return status; err2: destroy_workqueue(bitbang->workqueue); err1: return status; }
然后看这里是怎样注册spi主机控制器驱动的:
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int spi_register_master(struct spi_master *master)
{
。。。。。。。。。。。。。。。。
/*将spi添加到内核,这也是sys/class/Spi_master下产生Spi0,Spi1的原因*/
dev_set_name(&master->dev, "spi%u", master->bus_num);
status = device_add(&master->dev);
scan_boardinfo(master);
}
view plaincopy to clipboardprint? static void scan_boardinfo(struct spi_master *master) { struct boardinfo *bi; mutex_lock(&board_lock); /*遍历所有挂在board_list上的struct boardinfo*/ list_for_each_entry(bi, &board_list, list) { struct spi_board_info *chip = bi->board_info; unsigned n; /*遍历每个boardinfo管理的spi_board_info,如果设备的总线号与控制器的总线好相等,则创建新设备*/ for (n = bi->n_board_info; n > 0; n--, chip++) { if (chip->bus_num != master->bus_num) continue; (void) spi_new_device(master, chip); } } mutex_unlock(&board_lock); } static void scan_boardinfo(struct spi_master *master) { struct boardinfo *bi; mutex_lock(&board_lock); /*遍历所有挂在board_list上的struct boardinfo*/ list_for_each_entry(bi, &board_list, list) { struct spi_board_info *chip = bi->board_info; unsigned n; /*遍历每个boardinfo管理的spi_board_info,如果设备的总线号与控制器的总线好相等,则创建新设备*/ for (n = bi->n_board_info; n > 0; n--, chip++) { if (chip->bus_num != master->bus_num) continue; (void) spi_new_device(master, chip); } } mutex_unlock(&board_lock); }在移植的时候我们会在mach-smdk2440.c中的smdk2440_machine_init中添加spi_register_board_info
这个函数完成了将spi_board_info交由boardinfo管理,并把boardinfo挂载到board_list链表上。也就是说在系统初始化的时候将spi_device交由到挂在board_list上的boardinfo管理,在spi controller的driver注册的时候不但注册这个主机控制器的驱动,还要遍历这个主机控制器的总线上的spi_device,将总线上的spi_device全部注册进内核。当注册进内核并且spi_driver已经注册的时候,如果总线match成功,则会调用spi_driver的probe函数,这个将在后边进行分析。
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int __init
spi_register_board_info(struct spi_board_info const *info, unsigned n)
{
struct boardinfo *bi;
bi = kmalloc(sizeof(*bi) + n * sizeof *info, GFP_KERNEL);
if (!bi)
return -ENOMEM;
bi->nn_board_info = n;
memcpy(bi->board_info, info, n * sizeof *info);
mutex_lock(&board_lock);
list_add_tail(&bi->list, &board_list);
mutex_unlock(&board_lock);
return 0;
}
view plaincopy to clipboardprint? struct spi_device *spi_new_device(struct spi_master *master, struct spi_board_info *chip) { struct spi_device *proxy; int status; proxy = spi_alloc_device(master); if (!proxy) return NULL; WARN_ON(strlen(chip->modalias) >= sizeof(proxy->modalias)); /*初始化spi_device的各个字段*/ proxy->chipchip_select = chip->chip_select; proxy->max_speed_hz = chip->max_speed_hz; proxy->mode = chip->mode; proxy->irq = chip->irq; /*这里获得了spi_device的名字,这个modalias也是在我们移植时在mach-smdk2440.c中的s3c2410_spi0_board中设定的*/ strlcpy(proxy->modalias, chip->modalias, sizeof(proxy->modalias)); proxy->dev.platform_data = (void *) chip->platform_data; proxy->controller_data = chip->controller_data; proxy->controller_state = NULL; /*主要完成将spi_device添加到内核*/ status = spi_add_device(proxy); if (status < 0) { spi_dev_put(proxy); return NULL; } return proxy; } struct spi_device *spi_new_device(struct spi_master *master, struct spi_board_info *chip) { struct spi_device *proxy; int status; proxy = spi_alloc_device(master); if (!proxy) return NULL; WARN_ON(strlen(chip->modalias) >= sizeof(proxy->modalias)); /*初始化spi_device的各个字段*/ proxy->chip_select = chip->chip_select; proxy->max_speed_hz = chip->max_speed_hz; proxy->mode = chip->mode; proxy->irq = chip->irq; /*这里获得了spi_device的名字,这个modalias也是在我们移植时在mach-smdk2440.c中的s3c2410_spi0_board中设定的*/ strlcpy(proxy->modalias, chip->modalias, sizeof(proxy->modalias)); proxy->dev.platform_data = (void *) chip->platform_data; proxy->controller_data = chip->controller_data; proxy->controller_state = NULL; /*主要完成将spi_device添加到内核*/ status = spi_add_device(proxy); if (status < 0) { spi_dev_put(proxy); return NULL; } return proxy; }
下面来看分配spi_alloc_device的函数,主要完成了分配spi_device,并初始化spi->dev的一些字段。
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struct spi_device *spi_alloc_device(struct spi_master *master)
{
struct spi_device *spi;
struct device *dev = master->dev.parent;
if (!spi_master_get(master))
return NULL;
spi = kzalloc(sizeof *spi, GFP_KERNEL);
if (!spi) {
dev_err(dev, "cannot alloc spi_device\n");
spi_master_put(master);
return NULL;
}
spi->master = master;
spi->dev.parent = dev;
/*设置总线是spi_bus_type,下面会讲到spi_device与spi_driver是怎样match上的*/
spi->dev.bus = &spi_bus_type;
spi->dev.release = spidev_release;
device_initialize(&spi->dev);
return spi;
}
view plaincopy to clipboardprint? int spi_add_device(struct spi_device *spi) { static DEFINE_MUTEX(spi_add_lock); struct device *dev = spi->master->dev.parent; int status; /*spi_device的片选号不能大于spi控制器的片选数*/ if (spi->chip_select >= spi->master->num_chipselect) { dev_err(dev, "cs%d >= max %d\n", spi->chip_select, spi->master->num_chipselect); return -EINVAL; } /*这里设置是spi_device在Linux设备驱动模型中的name,也就是图中的spi0.0,而在/dev/下设备节点的名字是proxy->modalias中的名字*/ dev_set_name(&spi->dev, "%s.%u", dev_name(&spi->master->dev), spi->chip_select); mutex_lock(&spi_add_lock); /*如果总线上挂的设备已经有这个名字,则设置状态忙碌,并退出*/ if (bus_find_device_by_name(&spi_bus_type, NULL, dev_name(&spi->dev)) != NULL) { dev_err(dev, "chipselect %d already in use\n", spi->chip_select); status = -EBUSY; goto done; } /对spi_device的时钟等进行设置/ status = spi->master->setup(spi); if (status < 0) { dev_err(dev, "can't %s %s, status %d\n", "setup", dev_name(&spi->dev), status); goto done; } /*添加到内核*/ status = device_add(&spi->dev); if (status < 0) dev_err(dev, "can't %s %s, status %d\n", "add", dev_name(&spi->dev), status); else dev_dbg(dev, "registered child %s\n", dev_name(&spi->dev)); done: mutex_unlock(&spi_add_lock); return status; } static int s3c24xx_spi_setup(struct spi_device *spi) { 。。。。。。。。。。。。。。 ret = s3c24xx_spi_setupxfer(spi, NULL); 。。。。。。。。。。。。。。 } static int s3c24xx_spi_setupxfer(struct spi_device *spi, struct spi_transfer *t) { struct s3c24xx_spi *hw = to_hw(spi); unsigned int bpw; unsigned int hz; unsigned int div; /*设置了每字长的位数,发送速度*/ bpw = t ? t->bits_per_word : spi->bits_per_word; hz = t ? t->speed_hz : spi->max_speed_hz; if (bpw != 8) { dev_err(&spi->dev, "invalid bits-per-word (%d)\n", bpw); return -EINVAL; } /*设置分频值*/ div = clk_get_rate(hw->clk) / hz; /* is clk = pclk / (2 * (pre+1)), or is it * clk = (pclk * 2) / ( pre + 1) */ div /= 2; if (div > 0) div -= 1; if (div > 255) div = 255; dev_dbg(&spi->dev, "setting pre-scaler to %d (hz %d)\n", div, hz); writeb(div, hw->regs + S3C2410_SPPRE); spin_lock(&hw->bitbang.lock); if (!hw->bitbang.busy) { hw->bitbang.chipselect(spi, BITBANG_CS_INACTIVE); /* need to ndelay for 0.5 clocktick ? */ } spin_unlock(&hw->bitbang.lock); return 0; } int spi_add_device(struct spi_device *spi) { static DEFINE_MUTEX(spi_add_lock); struct device *dev = spi->master->dev.parent; int status; /*spi_device的片选号不能大于spi控制器的片选数*/ if (spi->chip_select >= spi->master->num_chipselect) { dev_err(dev, "cs%d >= max %d\n", spi->chip_select, spi->master->num_chipselect); return -EINVAL; } /*这里设置是spi_device在Linux设备驱动模型中的name,也就是图中的spi0.0,而在/dev/下设备节点的名字是proxy->modalias中的名字*/ dev_set_name(&spi->dev, "%s.%u", dev_name(&spi->master->dev), spi->chip_select); mutex_lock(&spi_add_lock); /*如果总线上挂的设备已经有这个名字,则设置状态忙碌,并退出*/ if (bus_find_device_by_name(&spi_bus_type, NULL, dev_name(&spi->dev)) != NULL) { dev_err(dev, "chipselect %d already in use\n", spi->chip_select); status = -EBUSY; goto done; } /对spi_device的时钟等进行设置/ status = spi->master->setup(spi); if (status < 0) { dev_err(dev, "can't %s %s, status %d\n", "setup", dev_name(&spi->dev), status); goto done; } /*添加到内核*/ status = device_add(&spi->dev); if (status < 0) dev_err(dev, "can't %s %s, status %d\n", "add", dev_name(&spi->dev), status); else dev_dbg(dev, "registered child %s\n", dev_name(&spi->dev)); done: mutex_unlock(&spi_add_lock); return status; } static int s3c24xx_spi_setup(struct spi_device *spi) { 。。。。。。。。。。。。。。 ret = s3c24xx_spi_setupxfer(spi, NULL); 。。。。。。。。。。。。。。 } static int s3c24xx_spi_setupxfer(struct spi_device *spi, struct spi_transfer *t) { struct s3c24xx_spi *hw = to_hw(spi); unsigned int bpw; unsigned int hz; unsigned int div; /*设置了每字长的位数,发送速度*/ bpw = t ? t->bits_per_word : spi->bits_per_word; hz = t ? t->speed_hz : spi->max_speed_hz; if (bpw != 8) { dev_err(&spi->dev, "invalid bits-per-word (%d)\n", bpw); return -EINVAL; } /*设置分频值*/ div = clk_get_rate(hw->clk) / hz; /* is clk = pclk / (2 * (pre+1)), or is it * clk = (pclk * 2) / ( pre + 1) */ div /= 2; if (div > 0) div -= 1; if (div > 255) div = 255; dev_dbg(&spi->dev, "setting pre-scaler to %d (hz %d)\n", div, hz); writeb(div, hw->regs + S3C2410_SPPRE); spin_lock(&hw->bitbang.lock); if (!hw->bitbang.busy) { hw->bitbang.chipselect(spi, BITBANG_CS_INACTIVE); /* need to ndelay for 0.5 clocktick ? */ } spin_unlock(&hw->bitbang.lock); return 0; }下面来看这个spi_driver是怎样注册的,又是与spi_device怎样match上的。
在spidev.c中:
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static int __init spidev_init(void)
{
int status;
BUILD_BUG_ON(N_SPI_MINORS > 256);
status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
if (status < 0)
return status;
spidev_class = class_create(THIS_MODULE, "spidev");
if (IS_ERR(spidev_class)) {
unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
return PTR_ERR(spidev_class);
}
status = spi_register_driver(&spidev_spi);
if (status < 0) {
class_destroy(spidev_class);
unregister_chrdev(SPIDEV_MAJOR, spidev_spi.driver.name);
}
return status;
}
view plaincopy to clipboardprint? static struct spi_driver spidev_spi = { .driver = { .name = "spidev", .owner = THIS_MODULE, }, .probe = spidev_probe, .remove = __devexit_p(spidev_remove), }; static struct spi_driver spidev_spi = { .driver = { .name = "spidev", .owner = THIS_MODULE, }, .probe = spidev_probe, .remove = __devexit_p(spidev_remove), };
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static struct spi_driver spidev_spi = {
.driver = {
.name = "spidev",
.owner = THIS_MODULE,
},
.probe = spidev_probe,
.remove = __devexit_p(spidev_remove),
};
view plaincopy to clipboardprint? static int __driver_attach(struct device *dev, void *data) { struct device_driver *drv = data; if (!driver_match_device(drv, dev)) return 0; if (dev->parent) /* Needed for USB */ down(&dev->parent->sem); down(&dev->sem); if (!dev->driver) driver_probe_device(drv, dev); up(&dev->sem); if (dev->parent) up(&dev->parent->sem); return 0; } static int __driver_attach(struct device *dev, void *data) { struct device_driver *drv = data; if (!driver_match_device(drv, dev)) return 0; if (dev->parent) /* Needed for USB */ down(&dev->parent->sem); down(&dev->sem); if (!dev->driver) driver_probe_device(drv, dev); up(&dev->sem); if (dev->parent) up(&dev->parent->sem); return 0; }匹配的时候调用的bus的match函数。
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struct bus_type spi_bus_type = {
.name = "spi",
.dev_attrs = spi_dev_attrs,
.match = spi_match_device,
.uevent = spi_uevent,
.suspend = spi_suspend,
.resume = spi_resume,
};
static int spi_match_device(struct device *dev, struct device_driver *drv)
{
const struct spi_device *spi = to_spi_device(dev);
return strcmp(spi->modalias, drv->name) == 0;
}
view plaincopy to clipboardprint? static int spi_drv_probe(struct device *dev) { const struct spi_driver *sdrv = to_spi_driver(dev->driver); return sdrv->probe(to_spi_device(dev)); } static int spi_drv_probe(struct device *dev) { const struct spi_driver *sdrv = to_spi_driver(dev->driver); return sdrv->probe(to_spi_device(dev)); }可以看大调用了具体的probe函数,这里实现了把spidev添加到device_list,这样这个虚拟的字符驱动就注册并初始化完毕。
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static int spidev_remove(struct spi_device *spi)
{
struct spidev_data *spidev = spi_get_drvdata(spi);
/* make sure ops on existing fds can abort cleanly */
spin_lock_irq(&spidev->spi_lock);
spidev->spi = NULL;
spi_set_drvdata(spi, NULL);
spin_unlock_irq(&spidev->spi_lock);
/* prevent new opens */
mutex_lock(&device_list_lock);
list_del(&spidev->device_entry);
device_destroy(spidev_class, spidev->devt);
clear_bit(MINOR(spidev->devt), minors);
if (spidev->users == 0)
kfree(spidev);
mutex_unlock(&device_list_lock);
return 0;
}
view plaincopy to clipboardprint? static struct file_operations spidev_fops = { .owner = THIS_MODULE, /* REVISIT switch to aio primitives, so that userspace * gets more complete API coverage. It'll simplify things * too, except for the locking. */ .write = spidev_write, .read = spidev_read, .unlocked_ioctl = spidev_ioctl, .open = spidev_open, .release = spidev_release, }; static struct file_operations spidev_fops = { .owner = THIS_MODULE, /* REVISIT switch to aio primitives, so that userspace * gets more complete API coverage. It'll simplify things * too, except for the locking. */ .write = spidev_write, .read = spidev_read, .unlocked_ioctl = spidev_ioctl, .open = spidev_open, .release = spidev_release, };到此为止spi子系统与spi_master,spi_device,spi_driver这个Linux设备驱动模型已经建立完了。
来源:http://blog.csdn.net/woshixingaaa/article/details/6574220
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