Linux内核4.14版本——SPI框架（7）——spidev.c分析

目录

1. 简介

3. spidev_fops

3.1 spidev_read

3.2 spidev_write

3.3 spidev_ioctl

4. 参考文章

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1. 简介

spidev.c文件：它是一个字符设备，满足字符设备的框架（注册设备、构造file_operation结构体、提供给虚拟文件系统的open、read、write函数接口）。

2. 驱动入口函数

​
static int __init spidev_init(void)
{
	int status;

	/* Claim our 256 reserved device numbers.  Then register a class
	 * that will key udev/mdev to add/remove /dev nodes.  Last, register
	 * the driver which manages those device numbers.
	 */
	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.driver.name);
		return PTR_ERR(spidev_class);
	}

	status = spi_register_driver(&spidev_spi_driver);
	if (status < 0) {
		class_destroy(spidev_class);
		unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
	}
	return status;
}
module_init(spidev_init);

static void __exit spidev_exit(void)
{
	spi_unregister_driver(&spidev_spi_driver);
	class_destroy(spidev_class);
	unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
}
module_exit(spidev_exit);

3. spidev_fops

static const 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,
	.compat_ioctl = spidev_compat_ioctl,
	.open =		spidev_open,
	.release =	spidev_release,
	.llseek =	no_llseek,
};

3.1 spidev_read

spidev_read->spidev_sync_read->spidev_sync->spi_sync->__spi_sync

3.2 spidev_write

spidev_write->spidev_sync_write->spidev_sync->spi_sync

3.3 spidev_ioctl

static long
spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
	int			retval = 0;
	struct spidev_data	*spidev;
	struct spi_device	*spi;
	u32			tmp;
	unsigned		n_ioc;
	struct spi_ioc_transfer	*ioc;

	/* Check type and command number */
	if (_IOC_TYPE(cmd) != SPI_IOC_MAGIC)
		return -ENOTTY;

	/* guard against device removal before, or while,
	 * we issue this ioctl.
	 */
	spidev = filp->private_data;
	spin_lock_irq(&spidev->spi_lock);
	spi = spi_dev_get(spidev->spi);
	spin_unlock_irq(&spidev->spi_lock);

	if (spi == NULL)
		return -ESHUTDOWN;

	/* use the buffer lock here for triple duty:
	 *  - prevent I/O (from us) so calling spi_setup() is safe;
	 *  - prevent concurrent SPI_IOC_WR_* from morphing
	 *    data fields while SPI_IOC_RD_* reads them;
	 *  - SPI_IOC_MESSAGE needs the buffer locked "normally".
	 */
	mutex_lock(&spidev->buf_lock);

	switch (cmd) {
	/* read requests */
	case SPI_IOC_RD_MODE:
		retval = put_user(spi->mode & SPI_MODE_MASK,
					(__u8 __user *)arg);
		break;
	case SPI_IOC_RD_MODE32:
		retval = put_user(spi->mode & SPI_MODE_MASK,
					(__u32 __user *)arg);
		break;
	case SPI_IOC_RD_LSB_FIRST:
		retval = put_user((spi->mode & SPI_LSB_FIRST) ?  1 : 0,
					(__u8 __user *)arg);
		break;
	case SPI_IOC_RD_BITS_PER_WORD:
		retval = put_user(spi->bits_per_word, (__u8 __user *)arg);
		break;
	case SPI_IOC_RD_MAX_SPEED_HZ:
		retval = put_user(spidev->speed_hz, (__u32 __user *)arg);
		break;

	/* write requests */
	case SPI_IOC_WR_MODE:
	case SPI_IOC_WR_MODE32:
		if (cmd == SPI_IOC_WR_MODE)
			retval = get_user(tmp, (u8 __user *)arg);
		else
			retval = get_user(tmp, (u32 __user *)arg);
		if (retval == 0) {
			u32	save = spi->mode;

			if (tmp & ~SPI_MODE_MASK) {
				retval = -EINVAL;
				break;
			}

			tmp |= spi->mode & ~SPI_MODE_MASK;
			spi->mode = (u16)tmp;
			retval = spi_setup(spi);
			if (retval < 0)
				spi->mode = save;
			else
				dev_dbg(&spi->dev, "spi mode %x\n", tmp);
		}
		break;
	case SPI_IOC_WR_LSB_FIRST:
		retval = get_user(tmp, (__u8 __user *)arg);
		if (retval == 0) {
			u32	save = spi->mode;

			if (tmp)
				spi->mode |= SPI_LSB_FIRST;
			else
				spi->mode &= ~SPI_LSB_FIRST;
			retval = spi_setup(spi);
			if (retval < 0)
				spi->mode = save;
			else
				dev_dbg(&spi->dev, "%csb first\n",
						tmp ? 'l' : 'm');
		}
		break;
	case SPI_IOC_WR_BITS_PER_WORD:
		retval = get_user(tmp, (__u8 __user *)arg);
		if (retval == 0) {
			u8	save = spi->bits_per_word;

			spi->bits_per_word = tmp;
			retval = spi_setup(spi);
			if (retval < 0)
				spi->bits_per_word = save;
			else
				dev_dbg(&spi->dev, "%d bits per word\n", tmp);
		}
		break;
	case SPI_IOC_WR_MAX_SPEED_HZ:
		retval = get_user(tmp, (__u32 __user *)arg);
		if (retval == 0) {
			u32	save = spi->max_speed_hz;

			spi->max_speed_hz = tmp;
			retval = spi_setup(spi);
			if (retval >= 0)
				spidev->speed_hz = tmp;
			else
				dev_dbg(&spi->dev, "%d Hz (max)\n", tmp);
			spi->max_speed_hz = save;
		}
		break;

	default:
		/* segmented and/or full-duplex I/O request */
		/* Check message and copy into scratch area */
		ioc = spidev_get_ioc_message(cmd,
				(struct spi_ioc_transfer __user *)arg, &n_ioc);
		if (IS_ERR(ioc)) {
			retval = PTR_ERR(ioc);
			break;
		}
		if (!ioc)
			break;	/* n_ioc is also 0 */

		/* translate to spi_message, execute */
		retval = spidev_message(spidev, ioc, n_ioc);
		kfree(ioc);
		break;
	}

	mutex_unlock(&spidev->buf_lock);
	spi_dev_put(spi);
	return retval;
}

设置spi的一些设备参数等。

4. 参考文章

linux SPI驱动开发_wangjie36的博客-CSDN博客

spi 驱动一：spi基本结构和spidev文件系统_老鹏-CSDN博客_spidev

AM335X——SPI设备驱动_hceng_linux-CSDN博客_am335x spi