写一个mx6ull 的linux lcd 驱动

好的，下面是一个简单的 MX6ULL Linux LCD 驱动框架，仅供参考：

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/of_platform.h>
#include <linux/of_device.h>
#include <linux/fb.h>
#include <linux/mutex.h>
#include <linux/io.h>
#include <linux/dma-mapping.h>

/* MX6ULL LCD 控制器寄存器宏定义 */
#define LCD_CTRL_BASE_ADDRESS 0x12345678

/* LCD 控制器寄存器偏移量 */
#define LCD_CTRL_REG1_OFFSET 0x00
#define LCD_CTRL_REG2_OFFSET 0x04
#define LCD_CTRL_REG3_OFFSET 0x08

/* MX6ULL LCD 驱动数据结构体 */
struct mx6ull_lcd {
    struct fb_info fb_info;
    struct mutex lock;
    void __iomem *regs;
    dma_addr_t dma_addr;
    u32 width;
    u32 height;
    u32 bpp;
};

/* 配置 MX6ULL LCD 控制器 */
static void mx6ull_lcd_controller_config(struct mx6ull_lcd *lcd)
{
    /* 配置控制器寄存器1 */
    writel((readl(lcd->regs + LCD_CTRL_REG1_OFFSET) & ~0x3) | lcd->bpp, lcd->regs + LCD_CTRL_REG1_OFFSET);

    /* 配置控制器寄存器2 */
    writel((readl(lcd->regs + LCD_CTRL_REG2_OFFSET) & ~0xFFFF) | (lcd->width << 16) | lcd->height, lcd->regs + LCD_CTRL_REG2_OFFSET);

    /* 配置控制器寄存器3 */
    // ...

    /* 打开 LCD 控制器 */
    // ...
}

/* MX6ULL LCD 驱动初始化函数 */
static int mx6ull_lcd_driver_probe(struct platform_device *pdev)
{
    struct mx6ull_lcd *lcd;
    struct fb_info *fb_info;

    /* 分配 MX6ULL LCD 驱动数据结构体 */
    lcd = devm_kzalloc(&pdev->dev, sizeof(struct mx6ull_lcd), GFP_KERNEL);
    if (!lcd)
        return -ENOMEM;

    /* 初始化 MX6ULL LCD 驱动数据结构体 */
    lcd->regs = devm_ioremap_resource(&pdev->dev, platform_get_resource(pdev, IORESOURCE_MEM, 0));
    if (IS_ERR(lcd->regs))
        return PTR_ERR(lcd->regs);

    mutex_init(&lcd->lock);

    /* 配置 MX6ULL LCD 控制器 */
    mx6ull_lcd_controller_config(lcd);

    /* 初始化 FB_INFO 结构体 */
    fb_info = &lcd->fb_info;
    fb_info->fbops = &mx6ull_lcd_fb_ops;
    fb_info->screen_base = dma_alloc_coherent(&pdev->dev, lcd->width * lcd->height * lcd->bpp / 8, &lcd->dma_addr, GFP_KERNEL);
    if (!fb_info->screen_base)
        return -ENOMEM;

    fb_info->fix = mx6ull_lcd_fix;
    fb_info->fix.line_length = lcd->width * lcd->bpp / 8;
    fb_info->var = mx6ull_lcd_var;
    fb_info->var.xres = lcd->width;
    fb_info->var.yres = lcd->height;
    fb_info->var.bits_per_pixel = lcd->bpp;
    fb_info->var.red.offset = 16;
    fb_info->var.red.length = 8;
    fb_info->var.green.offset = 8;
    fb_info->var.green.length = 8;
    fb_info->var.blue.offset = 0;
    fb_info->var.blue.length = 8;

    /* 注册 FB 设备 */
    if (register_framebuffer(fb_info) < 0) {
        dma_free_coherent(&pdev->dev, lcd->width * lcd->height * lcd->bpp / 8, fb_info->screen_base, lcd->dma_addr);
        return -EINVAL;
    }

    platform_set_drvdata(pdev, lcd);

    return 0;
}

/* MX6ULL LCD 驱动移除函数 */
static int mx6ull_lcd_driver_remove(struct platform_device *pdev)
{
    struct mx6ull_lcd *lcd = platform_get_drvdata(pdev);
    struct fb_info *fb_info = &lcd->fb_info;

    unregister_framebuffer(fb_info);
    dma_free_coherent(&pdev->dev, lcd->width * lcd->height * lcd->bpp / 8, fb_info->screen_base, lcd->dma_addr);

    return 0;
}

/* MX6ULL LCD 驱动设备树匹配列表 */
static const struct of_device_id mx6ull_lcd_driver_of_match[] = {
    { .compatible = "fsl,imx6ull-lcd", },
    {},
};
MODULE_DEVICE_TABLE(of, mx6ull_lcd_driver_of_match);

/* MX6ULL LCD 驱动平台驱动结构体 */
static struct platform_driver mx6ull_lcd_driver = {
    .probe = mx6ull_lcd_driver_probe,
    .remove = mx6ull_lcd_driver_remove,
    .driver = {
        .name = "mx6ull-lcd",
        .of_match_table = mx6ull_lcd_driver_of_match,
    },
};
module_platform_driver(mx6ull_lcd_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Your Name");
MODULE_DESCRIPTION("MX6ULL LCD Driver");

当然，以上代码只是一个简单的框架，具体的实现还需要根据具体的硬件平台和 LCD 控制器来进行相应的修改和实现。