虚拟触摸屏驱动+如何通过启动参数给驱动程序传递参数

   该驱动可用于没有触摸屏的设备上，加上虚拟FrameBuffer驱动(vfb)就可以模拟触摸屏。比如在Android系统的移植中，系统要正常启动，就必须要有FrameBuffer驱动和声卡驱动，此二者可使用drivers/video/vfb.c和sound/drivers/dummy.c两个虚拟驱动代替，系统正常起来后，可使用加上虚拟触摸屏驱动，就可以使用android-vnc-server()以启动VNC服务，然后使用VNC客户端将Android系统桌面显示到远端。配合虚拟触摸屏驱动，在远端就可以使用鼠标进行操作。

   由于触摸屏的大小参数必须和FrameBuffer的参数一致，所以驱动实现了使用启动参数传递大小参数，以此可作为如何通过启动参数给驱动程序传递参数的示例，代码如下：

/*
 * Virtual TouchScreen driver
 *
 * Copyright (C) 2011 Niu Tao <[e-mail]>
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License. See the file COPYING in the main directory of this archive for
 * more details.
 *
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/delay.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/input.h>

#define DRIVER_DESC "Virtual TouchScreen"

static struct input_dev *vts_dev;

#define VTS_MIN_XC 0
#define VTS_MAX_XC 320
#define VTS_MIN_YC 0
#define VTS_MAX_YC 480

static int __initdata vts_max_xc = VTS_MAX_XC;
static int __initdata vts_max_yc = VTS_MAX_YC;

#ifndef MODULE
static int __initdata vts_use = 0;
/**
 * parse options,format must be vts=widthxheigth
 */
static int __init vts_setup(char *str)
{
    char buf[64];
    char *p;
    int xc, yc;

    vts_use = 1;

    strncpy(buf, str, sizeof(buf));
    p = strchr(buf, 'x');
    if (!p)
        goto out;
    *p = '\0';
    xc = simple_strtoul(buf, NULL, 0);
    yc = simple_strtoul(p + 1, NULL, 0);

    if (!xc || !yc)
        goto out;

    vts_max_xc = xc;
    vts_max_yc = yc;
    return 1;
out:
    printk(KERN_WARNING "vts: option format must be like 'vts=widthxheigth'. "
            "use default config vts=%dx%d\n", vts_max_xc, vts_max_yc);
    return 0;
}
__setup("vts=", vts_setup);
#endif

static int __init vts_init(void)
{
    int err;

#ifndef MODULE
    if (!vts_use)
        return -ENODEV;
#endif
    vts_dev = input_allocate_device();
    if (!vts_dev) {
        printk(KERN_ERR "vts: not enough memory\n");
        err = -ENOMEM;
        goto fail1;
    }

    vts_dev->name = DRIVER_DESC;
    vts_dev->phys = "vts/input0";
    vts_dev->id.bustype = BUS_VIRTUAL;
    vts_dev->id.vendor = 0x0000;
    vts_dev->id.product = 0x0000;
    vts_dev->id.version = 0x0100;

    vts_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
    vts_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
    input_set_abs_params(vts_dev, ABS_X, VTS_MIN_XC, vts_max_xc, 0, 0);
    input_set_abs_params(vts_dev, ABS_Y, VTS_MIN_YC, vts_max_yc, 0, 0);

    err = input_register_device(vts_dev);
    if (err)
        goto fail2;

    return 0;

fail2:
    input_free_device(vts_dev);
fail1:
    return err;
}
module_init(vts_init);
#ifdef MODULE
static void __exit vts_exit(void)
{
    input_unregister_device(vts_dev);
    input_free_device(vts_dev);
}
module_exit(vts_exit);
#endif
MODULE_AUTHOR("Niu Tao ");
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_LICENSE("GPL");