v4l2架构专题模块handler分析 -- handler使能（2）s_ctrl

接着上一篇分析

int __v4l2_ctrl_handler_setup(struct v4l2_ctrl_handler *hdl)
{
	struct v4l2_ctrl *ctrl;
	int ret = 0;

	if (hdl == NULL)
		return 0;

	lockdep_assert_held(hdl->lock);

	list_for_each_entry(ctrl, &hdl->ctrls, node)
		ctrl->done = false;

	list_for_each_entry(ctrl, &hdl->ctrls, node) {
		struct v4l2_ctrl *master = ctrl->cluster[0];
		int i;

		/* Skip if this control was already handled by a cluster. */
		/* Skip button controls and read-only controls. */
		if (ctrl->done || ctrl->type == V4L2_CTRL_TYPE_BUTTON ||
		    (ctrl->flags & V4L2_CTRL_FLAG_READ_ONLY))
			continue;

		for (i = 0; i < master->ncontrols; i++) {
			if (master->cluster[i]) {
				cur_to_new(master->cluster[i]);
				master->cluster[i]->is_new = 1;
				master->cluster[i]->done = true;
			}
		}
		ret = call_op(master, s_ctrl);
		if (ret)
			break;
	}

	return ret;
}

对于每个ctrl都会调用s_ctrl，而s_ctrl则是来源于注册ctrl时候的ops，以下面这个ctrl为例

static const struct v4l2_ctrl_ops os04a10_ctrl_ops = {
	.s_ctrl = os04a10_set_ctrl,
};

v4l2_ctrl_new_std(handler, &os04a10_ctrl_ops, V4L2_CID_VBLANK, vblank_def,
				    OS04A10_VTS_MAX - mode->height,
				    1, vblank_def);

则s_ctrl就是os04a10_set_ctrl

static int os04a10_set_ctrl(struct v4l2_ctrl *ctrl)
{
	...

	switch (ctrl->id) {
	...
	case V4L2_CID_VBLANK:
		ret = os04a10_write_reg(os04a10->client, OS04A10_REG_VTS,
					OS04A10_REG_VALUE_16BIT,
					ctrl->val + os04a10->cur_mode->height);
		dev_dbg(&client->dev, "set vblank 0x%xn",
			ctrl->val);
		break;
	...
	}

	return ret;
}

最后对应的就是操作寄存器

最后

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