linux sysfs实现hdmi开关

平台是全志A10 android4.0

linux-3.0/drivers/video/sun4i/disp/dev_disp.c

static ssize_t show_hdmi_ctrl(struct device *dev, struct device_attribute *attr, char *buf)
{
    return sprintf(buf, "%s\n", suspend_status & 1 ? "off":"on");
}

static ssize_t set_hdmi_ctrl(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
    unsigned long val = 0;
    if (count <= 0)
        return 0;
    val = simple_strtoul(buf, NULL, 0);
    /*
     * sscanf用于解析echo 0x00,0x2 > hdmi_ctrl这类命令。
     * sscanf(buf, "%d,%d", &i2c_reg,&i2c_data);
     */
    if (val)
        backlight_early_suspend(NULL);
    else
        backlight_late_resume(NULL);

    return count;
}

static DEVICE_ATTR(hdmictrl, S_IRUGO | S_IWUSR, show_hdmi_ctrl, set_hdmion_ctrl);
static struct attribute *dev_attrs[] = {
    &dev_attr_hdmion.attr,
    NULL,
};

static struct attribute_group dev_attr_grp = {
    .attrs = dev_attrs,
};

static int __init disp_probe(struct platform_device *pdev)//called when platform_driver_register
{
    int err = 0;
    sysfs_create_group(&pdev->dev.kobj, &dev_attr_grp);
    err = sysfs_create_group(&pdev->dev.kobj, &dev_attr_grp);
    if (err < 0)
    {
        printk("disp : sysfs_create_group err\n");
        return err;
    }

    return 0;
}

static int disp_remove(struct platform_device *pdev)
{
    sysfs_remove_group(&pdev->dev.kobj, &dev_attr_grp);

    return 0;
}

HDMI关：echo 1 > /sys/devices/platform/disp/hdmi_ctrl
HDMI开：echo 0 > /sys/devices/platform/disp/hdmi_ctrl