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	Mon, 23 May 2016 06:36:35 -0400
Subject: Re: [PATCH v2 2/2] media: Add a driver for the ov5645 camera sensor.
To: Todor Tomov <todor.tomov@linaro.org>, robh+dt@kernel.org,
	pawel.moll@arm.com, mark.rutland@arm.com,
	ijc+devicetree@hellion.org.uk, galak@codeaurora.org,
	devicetree@vger.kernel.org, mchehab@osg.samsung.com,
	geert@linux-m68k.org, matrandg@cisco.com,
	linux-media@vger.kernel.org
References: <1463572208-8826-1-git-send-email-todor.tomov@linaro.org>
 <1463572208-8826-3-git-send-email-todor.tomov@linaro.org>
Cc: laurent.pinchart@ideasonboard.com
From: Hans Verkuil <hverkuil@xs4all.nl>
Message-ID: <5742DD2A.3010706@xs4all.nl>
Date: Mon, 23 May 2016 12:36:26 +0200
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Sender: linux-media-owner@vger.kernel.org
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Hi Todor,

Thanks for the patch series! I got a few comments:

On 05/18/2016 01:50 PM, Todor Tomov wrote:
> The ov5645 sensor from Omnivision supports up to 2592x1944
> and CSI2 interface.
> 
> The driver adds support for the following modes:
> - 1280x960
> - 1920x1080
> - 2592x1944
> 
> Output format is packed 8bit UYVY.
> 
> Signed-off-by: Todor Tomov <todor.tomov@linaro.org>
> ---
>  drivers/media/i2c/Kconfig  |   11 +
>  drivers/media/i2c/Makefile |    1 +
>  drivers/media/i2c/ov5645.c | 1425 ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 1437 insertions(+)
>  create mode 100644 drivers/media/i2c/ov5645.c

<snip>

> 
> +static int ov5645_change_mode(struct ov5645 *ov5645, enum ov5645_mode mode)
> +{
> +	struct reg_value *settings;
> +	u32 num_settings;
> +	int ret = 0;
> +
> +	settings = ov5645_mode_info_data[mode].data;
> +	num_settings = ov5645_mode_info_data[mode].data_size;
> +	ret = ov5645_set_register_array(ov5645, settings, num_settings);

Just do 'return ov5645_set_register_array(ov5645, settings, num_settings);'
No need for the 'ret' variable.

> +
> +	return ret;
> +}
> +
> +static int ov5645_set_power_on(struct ov5645 *ov5645)
> +{
> +	int ret = 0;
> +
> +	dev_dbg(ov5645->dev, "%s: Enter\n", __func__);
> +
> +	ret = clk_prepare_enable(ov5645->xclk);
> +	if (ret < 0) {
> +		dev_err(ov5645->dev, "clk prepare enable failed\n");
> +		return ret;
> +	}
> +
> +	ret = ov5645_regulators_enable(ov5645);
> +	if (ret < 0) {
> +		clk_disable_unprepare(ov5645->xclk);
> +		return ret;
> +	}
> +
> +	usleep_range(5000, 15000);
> +	if (ov5645->pwdn_gpio)
> +		gpiod_set_value_cansleep(ov5645->pwdn_gpio, 1);
> +
> +	usleep_range(1000, 2000);
> +	if (ov5645->rst_gpio)
> +		gpiod_set_value_cansleep(ov5645->rst_gpio, 1);
> +	msleep(20);
> +
> +	return ret;
> +}
> +
> +static void ov5645_set_power_off(struct ov5645 *ov5645)
> +{
> +	dev_dbg(ov5645->dev, "%s: Enter\n", __func__);
> +
> +	if (ov5645->rst_gpio)
> +		gpiod_set_value_cansleep(ov5645->rst_gpio, 0);
> +	if (ov5645->pwdn_gpio)
> +		gpiod_set_value_cansleep(ov5645->pwdn_gpio, 0);
> +	ov5645_regulators_disable(ov5645);
> +	clk_disable_unprepare(ov5645->xclk);
> +}
> +
> +static int ov5645_s_power(struct v4l2_subdev *sd, int on)
> +{
> +	struct ov5645 *ov5645 = to_ov5645(sd);
> +	int ret = 0;
> +
> +	dev_dbg(ov5645->dev, "%s: on = %d\n", __func__, on);
> +
> +	mutex_lock(&ov5645->power_lock);
> +
> +	/* If the power count is modified from 0 to != 0 or from != 0 to 0,
> +	 * update the power state.
> +	 */
> +	if (ov5645->power == !on) {
> +		if (on) {
> +			ret = ov5645_set_power_on(ov5645);
> +			if (ret < 0) {
> +				dev_err(ov5645->dev, "could not set power %s\n",
> +					on ? "on" : "off");
> +				goto exit;
> +			}
> +
> +			ret = ov5645_init(ov5645);
> +			if (ret < 0) {
> +				dev_err(ov5645->dev,
> +					"could not set init registers\n");
> +				goto exit;
> +			}
> +
> +			ov5645_write_reg(ov5645, OV5645_SYSTEM_CTRL0,
> +					 OV5645_SYSTEM_CTRL0_STOP);
> +		} else {
> +			ov5645_set_power_off(ov5645);
> +		}
> +
> +		/* Update the power count. */
> +		ov5645->power += on ? 1 : -1;

Huh? Is ov5645->power a bool or a counter? If it is a counter then this line
should be outside this 'if'. If it is a bool, then the comments (and the
power field itself!) should be updated.

As far as I can tell, the 'power' field should be a bool and everything should
be updated accordingly.


> +		WARN_ON(ov5645->power < 0);
> +	}
> +
> +exit:
> +	mutex_unlock(&ov5645->power_lock);
> +
> +	return ret;
> +}
> +
> +
> +static int ov5645_set_saturation(struct ov5645 *ov5645, s32 value)
> +{
> +	u32 reg_value = (value * 0x10) + 0x40;
> +	int ret = 0;
> +
> +	ret |= ov5645_write_reg(ov5645, OV5645_SDE_SAT_U, reg_value);
> +	ret |= ov5645_write_reg(ov5645, OV5645_SDE_SAT_V, reg_value);
> +
> +	dev_dbg(ov5645->dev, "%s: value = %d\n", __func__, value);
> +
> +	return ret;
> +}
> +
> +static int ov5645_set_hflip(struct ov5645 *ov5645, s32 value)
> +{
> +	u8 val;
> +
> +	ov5645_read_reg(ov5645, OV5645_TIMING_TC_REG21, &val);
> +	if (value == 0)
> +		val &= ~(OV5645_SENSOR_MIRROR);
> +	else
> +		val |= (OV5645_SENSOR_MIRROR);
> +
> +	dev_dbg(ov5645->dev, "%s: value = %d\n", __func__, value);
> +
> +	return ov5645_write_reg(ov5645, OV5645_TIMING_TC_REG21, val);
> +}
> +
> +static int ov5645_set_vflip(struct ov5645 *ov5645, s32 value)
> +{
> +	u8 val;
> +
> +	ov5645_read_reg(ov5645, OV5645_TIMING_TC_REG20, &val);
> +	if (value == 0)
> +		val |= (OV5645_SENSOR_VFLIP | OV5645_ISP_VFLIP);
> +	else
> +		val &= ~(OV5645_SENSOR_VFLIP | OV5645_ISP_VFLIP);
> +
> +	dev_dbg(ov5645->dev, "%s: value = %d\n", __func__, value);
> +
> +	return ov5645_write_reg(ov5645, OV5645_TIMING_TC_REG20, val);
> +}
> +
> +static int ov5645_set_test_pattern(struct ov5645 *ov5645, s32 value)
> +{
> +	u8 val;
> +
> +	ov5645_read_reg(ov5645, OV5645_PRE_ISP_TEST_SETTING_1, &val);
> +
> +	if (value) {
> +		val &= ~OV5645_SET_TEST_PATTERN(OV5645_TEST_PATTERN_MASK);
> +		val |= OV5645_SET_TEST_PATTERN(value - 1);
> +		val |= OV5645_TEST_PATTERN_ENABLE;
> +	} else {
> +		val &= ~OV5645_TEST_PATTERN_ENABLE;
> +	}
> +
> +	dev_dbg(ov5645->dev, "%s: value = %d\n", __func__, value);
> +
> +	return ov5645_write_reg(ov5645, OV5645_PRE_ISP_TEST_SETTING_1, val);
> +}
> +
> +static const char * const ov5645_test_pattern_menu[] = {
> +	"Disabled",
> +	"Vertical Color Bars",
> +	"Random Data",
> +	"Color Square",
> +	"Black Image",
> +};
> +
> +static int ov5645_set_awb(struct ov5645 *ov5645, s32 enable_auto)
> +{
> +	u8 val;
> +
> +	ov5645_read_reg(ov5645, OV5645_AWB_MANUAL_CONTROL, &val);
> +	if (enable_auto)
> +		val &= ~OV5645_AWB_MANUAL_ENABLE;
> +	else
> +		val |= OV5645_AWB_MANUAL_ENABLE;
> +
> +	dev_dbg(ov5645->dev, "%s: enable_auto = %d\n", __func__, enable_auto);
> +
> +	return ov5645_write_reg(ov5645, OV5645_AWB_MANUAL_CONTROL, val);
> +}
> +
> +static int ov5645_s_ctrl(struct v4l2_ctrl *ctrl)
> +{
> +	struct ov5645 *ov5645 = container_of(ctrl->handler,
> +					     struct ov5645, ctrls);
> +	int ret = -EINVAL;
> +
> +	mutex_lock(&ov5645->power_lock);
> +	if (ov5645->power == 0) {
> +		mutex_unlock(&ov5645->power_lock);
> +		return 0;
> +	}
> +
> +	switch (ctrl->id) {
> +	case V4L2_CID_SATURATION:
> +		ret = ov5645_set_saturation(ov5645, ctrl->val);
> +		break;
> +	case V4L2_CID_AUTO_WHITE_BALANCE:
> +		ret = ov5645_set_awb(ov5645, ctrl->val);
> +		break;
> +	case V4L2_CID_AUTOGAIN:
> +		ret = ov5645_set_agc_mode(ov5645, ctrl->val);
> +		break;
> +	case V4L2_CID_EXPOSURE_AUTO:
> +		ret = ov5645_set_aec_mode(ov5645, ctrl->val);
> +		break;
> +	case V4L2_CID_TEST_PATTERN:
> +		ret = ov5645_set_test_pattern(ov5645, ctrl->val);
> +		break;
> +	case V4L2_CID_HFLIP:
> +		ret = ov5645_set_hflip(ov5645, ctrl->val);
> +		break;
> +	case V4L2_CID_VFLIP:
> +		ret = ov5645_set_vflip(ov5645, ctrl->val);
> +		break;
> +	}
> +
> +	mutex_unlock(&ov5645->power_lock);
> +
> +	return ret;
> +}
> +
> +static struct v4l2_ctrl_ops ov5645_ctrl_ops = {
> +	.s_ctrl = ov5645_s_ctrl,
> +};
> +
> +static int ov5645_enum_mbus_code(struct v4l2_subdev *sd,
> +				 struct v4l2_subdev_pad_config *cfg,
> +				 struct v4l2_subdev_mbus_code_enum *code)
> +{
> +	struct ov5645 *ov5645 = to_ov5645(sd);
> +
> +	if (code->index > 0)
> +		return -EINVAL;
> +
> +	code->code = ov5645->fmt.code;
> +
> +	return 0;
> +}
> +
> +static int ov5645_enum_frame_size(struct v4l2_subdev *subdev,
> +				  struct v4l2_subdev_pad_config *cfg,
> +				  struct v4l2_subdev_frame_size_enum *fse)
> +{
> +	if (fse->index >= OV5645_MODE_MAX)
> +		return -EINVAL;
> +
> +	fse->min_width = ov5645_mode_info_data[fse->index].width;
> +	fse->max_width = ov5645_mode_info_data[fse->index].width;
> +	fse->min_height = ov5645_mode_info_data[fse->index].height;
> +	fse->max_height = ov5645_mode_info_data[fse->index].height;
> +
> +	return 0;
> +}
> +
> +static struct v4l2_mbus_framefmt *
> +__ov5645_get_pad_format(struct ov5645 *ov5645,
> +			struct v4l2_subdev_pad_config *cfg,
> +			unsigned int pad,
> +			enum v4l2_subdev_format_whence which)
> +{
> +	switch (which) {
> +	case V4L2_SUBDEV_FORMAT_TRY:
> +		return v4l2_subdev_get_try_format(&ov5645->sd, cfg, pad);
> +	case V4L2_SUBDEV_FORMAT_ACTIVE:
> +		return &ov5645->fmt;
> +	default:
> +		return NULL;
> +	}
> +}
> +
> +static int ov5645_get_format(struct v4l2_subdev *sd,
> +			     struct v4l2_subdev_pad_config *cfg,
> +			     struct v4l2_subdev_format *format)
> +{
> +	struct ov5645 *ov5645 = to_ov5645(sd);
> +
> +	format->format = *__ov5645_get_pad_format(ov5645, cfg, format->pad,
> +						  format->which);
> +	return 0;
> +}
> +
> +static struct v4l2_rect *
> +__ov5645_get_pad_crop(struct ov5645 *ov5645, struct v4l2_subdev_pad_config *cfg,
> +		      unsigned int pad, enum v4l2_subdev_format_whence which)
> +{
> +	switch (which) {
> +	case V4L2_SUBDEV_FORMAT_TRY:
> +		return v4l2_subdev_get_try_crop(&ov5645->sd, cfg, pad);
> +	case V4L2_SUBDEV_FORMAT_ACTIVE:
> +		return &ov5645->crop;
> +	default:
> +		return NULL;
> +	}
> +}
> +
> +static enum ov5645_mode ov5645_find_nearest_mode(struct ov5645 *ov5645,
> +						 int width, int height)
> +{
> +	int i;
> +
> +	for (i = OV5645_MODE_MAX; i >= 0; i--) {
> +		if (ov5645_mode_info_data[i].width <= width &&
> +		    ov5645_mode_info_data[i].height <= height)
> +			break;
> +	}
> +
> +	if (i < 0)
> +		i = 0;
> +
> +	return (enum ov5645_mode)i;
> +}
> +
> +static int ov5645_set_format(struct v4l2_subdev *sd,
> +			     struct v4l2_subdev_pad_config *cfg,
> +			     struct v4l2_subdev_format *format)
> +{
> +	struct ov5645 *ov5645 = to_ov5645(sd);
> +	struct v4l2_mbus_framefmt *__format;
> +	struct v4l2_rect *__crop;
> +	enum ov5645_mode new_mode;
> +
> +	__crop = __ov5645_get_pad_crop(ov5645, cfg, format->pad,
> +			format->which);
> +
> +	new_mode = ov5645_find_nearest_mode(ov5645,
> +			format->format.width, format->format.height);
> +	__crop->width = ov5645_mode_info_data[new_mode].width;
> +	__crop->height = ov5645_mode_info_data[new_mode].height;
> +
> +	ov5645->current_mode = new_mode;
> +
> +	__format = __ov5645_get_pad_format(ov5645, cfg, format->pad,
> +			format->which);
> +	__format->width = __crop->width;
> +	__format->height = __crop->height;
> +
> +	return 0;
> +}
> +
> +static int ov5645_get_selection(struct v4l2_subdev *sd,
> +			   struct v4l2_subdev_pad_config *cfg,
> +			   struct v4l2_subdev_selection *sel)
> +{
> +	struct ov5645 *ov5645 = to_ov5645(sd);
> +
> +	if (sel->target != V4L2_SEL_TGT_CROP)
> +		return -EINVAL;
> +
> +	sel->r = *__ov5645_get_pad_crop(ov5645, cfg, sel->pad,
> +					    sel->which);
> +	return 0;
> +}
> +
> +static int ov5645_registered(struct v4l2_subdev *subdev)
> +{
> +	struct i2c_client *client = v4l2_get_subdevdata(subdev);
> +	struct ov5645 *ov5645 = to_ov5645(subdev);
> +	u8 chip_id_high, chip_id_low;
> +	int ret;
> +
> +	ov5645_s_power(&ov5645->sd, true);
> +
> +	ret = ov5645_read_reg(ov5645, OV5645_CHIP_ID_HIGH_REG, &chip_id_high);
> +	if (ret < 0 || chip_id_high != OV5645_CHIP_ID_HIGH) {
> +		dev_err(ov5645->dev, "could not read ID high\n");
> +		ret = -ENODEV;
> +		goto reg_power_off;
> +	}
> +	ret = ov5645_read_reg(ov5645, OV5645_CHIP_ID_LOW_REG, &chip_id_low);
> +	if (ret < 0 || chip_id_low != OV5645_CHIP_ID_LOW) {
> +		dev_err(ov5645->dev, "could not read ID low\n");
> +		ret = -ENODEV;
> +		goto reg_power_off;
> +	}
> +
> +	dev_info(&client->dev, "OV5645 detected at address 0x%02x\n",
> +		 client->addr);
> +
> +	ov5645_s_power(&ov5645->sd, false);
> +
> +	return 0;
> +
> +reg_power_off:
> +	ov5645_s_power(&ov5645->sd, false);
> +	return ret;
> +}

Why do this here instead of in the probe() function? I see no reason for
having a ov5645_registered() function.

> +
> +static int ov5645_s_stream(struct v4l2_subdev *subdev, int enable)
> +{
> +	struct ov5645 *ov5645 = to_ov5645(subdev);
> +	int ret;
> +
> +	dev_dbg(ov5645->dev, "%s: enable = %d\n", __func__, enable);
> +
> +	if (enable) {
> +		ret = ov5645_change_mode(ov5645, ov5645->current_mode);
> +		if (ret < 0) {
> +			dev_err(ov5645->dev, "could not set mode %d\n",
> +				ov5645->current_mode);
> +			return ret;
> +		}
> +		ret = v4l2_ctrl_handler_setup(&ov5645->ctrls);
> +		if (ret < 0) {
> +			dev_err(ov5645->dev, "could not sync v4l2 controls\n");
> +			return ret;
> +		}
> +		ov5645_write_reg(ov5645, OV5645_SYSTEM_CTRL0,
> +				 OV5645_SYSTEM_CTRL0_START);
> +	} else {
> +		ov5645_write_reg(ov5645, OV5645_SYSTEM_CTRL0,
> +				 OV5645_SYSTEM_CTRL0_STOP);
> +	}
> +
> +	return 0;
> +}
> +
> +static struct v4l2_subdev_core_ops ov5645_core_ops = {
> +	.s_power = ov5645_s_power,
> +};
> +
> +static struct v4l2_subdev_video_ops ov5645_video_ops = {
> +	.s_stream = ov5645_s_stream,
> +};
> +
> +static struct v4l2_subdev_pad_ops ov5645_subdev_pad_ops = {
> +	.enum_mbus_code = ov5645_enum_mbus_code,
> +	.enum_frame_size = ov5645_enum_frame_size,
> +	.get_fmt = ov5645_get_format,
> +	.set_fmt = ov5645_set_format,
> +	.get_selection = ov5645_get_selection,
> +};
> +
> +static struct v4l2_subdev_ops ov5645_subdev_ops = {
> +	.core = &ov5645_core_ops,
> +	.video = &ov5645_video_ops,
> +	.pad = &ov5645_subdev_pad_ops,
> +};
> +
> +static const struct v4l2_subdev_internal_ops ov5645_subdev_internal_ops = {
> +	.registered = ov5645_registered,
> +};
> +
> +static int ov5645_probe(struct i2c_client *client,
> +			const struct i2c_device_id *id)
> +{
> +	struct device *dev = &client->dev;
> +	struct device_node *endpoint;
> +	struct ov5645 *ov5645;
> +	int ret = 0;
> +
> +	ov5645 = devm_kzalloc(dev, sizeof(struct ov5645), GFP_KERNEL);
> +	if (!ov5645)
> +		return -ENOMEM;
> +
> +	ov5645->i2c_client = client;
> +	ov5645->dev = dev;
> +	ov5645->fmt.code = MEDIA_BUS_FMT_UYVY8_2X8;
> +	ov5645->fmt.width = 1920;
> +	ov5645->fmt.height = 1080;
> +	ov5645->fmt.field = V4L2_FIELD_NONE;
> +	ov5645->fmt.colorspace = V4L2_COLORSPACE_SRGB;
> +	ov5645->current_mode = OV5645_MODE_1080P;
> +
> +	endpoint = of_graph_get_next_endpoint(dev->of_node, NULL);
> +	if (!endpoint) {
> +		dev_err(dev, "endpoint node not found\n");
> +		return -EINVAL;
> +	}
> +
> +	ret = v4l2_of_parse_endpoint(endpoint, &ov5645->ep);
> +	if (ret < 0) {
> +		dev_err(dev, "parsing endpoint node failed\n");
> +		return ret;
> +	}
> +	if (ov5645->ep.bus_type != V4L2_MBUS_CSI2) {
> +		dev_err(dev, "invalid bus type, must be CSI2\n");
> +		of_node_put(endpoint);
> +		return -EINVAL;
> +	}
> +	of_node_put(endpoint);
> +
> +	/* get system clock (xclk) */
> +	ov5645->xclk = devm_clk_get(dev, "xclk");
> +	if (IS_ERR(ov5645->xclk)) {
> +		dev_err(dev, "could not get xclk");
> +		return PTR_ERR(ov5645->xclk);
> +	}
> +
> +	ov5645->io_regulator = devm_regulator_get(dev, "dovdd");
> +	if (IS_ERR(ov5645->io_regulator)) {
> +		switch(PTR_ERR(ov5645->io_regulator)) {
> +		case -ENODEV:
> +			/* Regulator is optional so this is ok - continue */
> +			ov5645->io_regulator = NULL;
> +			dev_dbg(dev, "io regulator not present\n");
> +			break;
> +		case -EPROBE_DEFER:
> +			dev_dbg(dev, "io regulator probe defered\n");
> +			return -EPROBE_DEFER;
> +		default:
> +			dev_err(dev, "cannot get io regulator\n");
> +			return PTR_ERR(ov5645->io_regulator);
> +		}
> +	} else {
> +		ret = regulator_set_voltage(ov5645->io_regulator,
> +					     OV5645_VOLTAGE_DIGITAL_IO,
> +					     OV5645_VOLTAGE_DIGITAL_IO);
> +		if (ret < 0) {
> +			dev_err(dev, "cannot set io voltage\n");
> +			return ret;
> +		}
> +	}
> +
> +	ov5645->core_regulator = devm_regulator_get(dev, "dvdd");
> +	if (IS_ERR(ov5645->core_regulator)) {
> +		switch(PTR_ERR(ov5645->core_regulator)) {
> +		case -ENODEV:
> +			/* Regulator is optional so this is ok - continue */
> +			ov5645->core_regulator = NULL;
> +			dev_dbg(dev, "core regulator not present\n");
> +			break;
> +		case -EPROBE_DEFER:
> +			dev_dbg(dev, "core regulator probe defered\n");
> +			return -EPROBE_DEFER;
> +		default:
> +			dev_err(dev, "cannot get core regulator\n");
> +			return PTR_ERR(ov5645->core_regulator);
> +		}
> +	} else {
> +		ret = regulator_set_voltage(ov5645->core_regulator,
> +					     OV5645_VOLTAGE_DIGITAL_CORE,
> +					     OV5645_VOLTAGE_DIGITAL_CORE);
> +		if (ret < 0) {
> +			dev_err(dev, "cannot set core voltage\n");
> +			return ret;
> +		}
> +	}
> +
> +	ov5645->analog_regulator = devm_regulator_get(dev, "avdd");
> +	if (IS_ERR(ov5645->analog_regulator)) {
> +		switch(PTR_ERR(ov5645->analog_regulator)) {
> +		case -ENODEV:
> +			/* Regulator is optional so this is ok - continue */
> +			ov5645->analog_regulator = NULL;
> +			dev_dbg(dev, "analog regulator not present\n");
> +			break;
> +		case -EPROBE_DEFER:
> +			dev_dbg(dev, "analog regulator probe defered\n");
> +			return -EPROBE_DEFER;
> +		default:
> +			dev_err(dev, "cannot get analog regulator\n");
> +			return PTR_ERR(ov5645->analog_regulator);
> +		}
> +	} else {
> +		ret = regulator_set_voltage(ov5645->analog_regulator,
> +					     OV5645_VOLTAGE_ANALOG,
> +					     OV5645_VOLTAGE_ANALOG);
> +		if (ret < 0) {
> +			dev_err(dev, "cannot set analog voltage\n");
> +			return ret;
> +		}
> +	}
> +
> +	ov5645->pwdn_gpio = devm_gpiod_get(dev, "pwdn", GPIOD_OUT_LOW);
> +	if (IS_ERR(ov5645->pwdn_gpio)) {
> +		switch(PTR_ERR(ov5645->pwdn_gpio)) {
> +		case -ENOENT:
> +			/* GPIO is optional so this is ok - continue */
> +			ov5645->pwdn_gpio = NULL;
> +			dev_dbg(dev, "power down gpio not present\n");
> +			break;
> +		case -EPROBE_DEFER:
> +			dev_dbg(dev, "power down gpio probe defered\n");
> +			return -EPROBE_DEFER;
> +		default:
> +			dev_err(dev, "cannot get power down gpio\n");
> +			return PTR_ERR(ov5645->pwdn_gpio);
> +		}
> +	}
> +
> +	ov5645->rst_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
> +	if (IS_ERR(ov5645->rst_gpio)) {
> +		switch(PTR_ERR(ov5645->rst_gpio)) {
> +		case -ENOENT:
> +			/* GPIO is optional so this is ok - continue */
> +			ov5645->rst_gpio = NULL;
> +			dev_dbg(dev, "reset gpio not present\n");
> +			break;
> +		case -EPROBE_DEFER:
> +			dev_dbg(dev, "reset gpio probe defered\n");
> +			return -EPROBE_DEFER;
> +		default:
> +			dev_err(dev, "cannot get reset gpio\n");
> +			return PTR_ERR(ov5645->rst_gpio);
> +		}
> +	}
> +
> +	mutex_init(&ov5645->power_lock);
> +
> +	v4l2_ctrl_handler_init(&ov5645->ctrls, 7);
> +	ov5645->saturation = v4l2_ctrl_new_std(&ov5645->ctrls, &ov5645_ctrl_ops,
> +				V4L2_CID_SATURATION, -4, 4, 1, 0);
> +	ov5645->hflip = v4l2_ctrl_new_std(&ov5645->ctrls, &ov5645_ctrl_ops,
> +				V4L2_CID_HFLIP, 0, 1, 1, 0);
> +	ov5645->vflip = v4l2_ctrl_new_std(&ov5645->ctrls, &ov5645_ctrl_ops,
> +				V4L2_CID_VFLIP, 0, 1, 1, 0);
> +	ov5645->autogain = v4l2_ctrl_new_std(&ov5645->ctrls, &ov5645_ctrl_ops,
> +				V4L2_CID_AUTOGAIN, 0, 1, 1, 1);
> +	ov5645->autoexposure = v4l2_ctrl_new_std_menu(&ov5645->ctrls,
> +				&ov5645_ctrl_ops, V4L2_CID_EXPOSURE_AUTO,
> +				V4L2_EXPOSURE_MANUAL, 0, V4L2_EXPOSURE_AUTO);
> +	ov5645->awb = v4l2_ctrl_new_std(&ov5645->ctrls, &ov5645_ctrl_ops,
> +				V4L2_CID_AUTO_WHITE_BALANCE, 0, 1, 1, 1);
> +	ov5645->pattern = v4l2_ctrl_new_std_menu_items(&ov5645->ctrls,
> +				&ov5645_ctrl_ops, V4L2_CID_TEST_PATTERN,
> +				ARRAY_SIZE(ov5645_test_pattern_menu) - 1, 0, 0,
> +				ov5645_test_pattern_menu);
> +
> +	ov5645->sd.ctrl_handler = &ov5645->ctrls;
> +
> +	if (ov5645->ctrls.error) {
> +		dev_err(dev, "%s: control initialization error %d\n",
> +		       __func__, ov5645->ctrls.error);
> +		ret = ov5645->ctrls.error;
> +		goto free_ctrl;
> +	}
> +
> +	v4l2_i2c_subdev_init(&ov5645->sd, client, &ov5645_subdev_ops);
> +	ov5645->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
> +	ov5645->pad.flags = MEDIA_PAD_FL_SOURCE;
> +	ov5645->sd.internal_ops = &ov5645_subdev_internal_ops;
> +
> +	ret = media_entity_init(&ov5645->sd.entity, 1, &ov5645->pad, 0);
> +	if (ret < 0) {
> +		dev_err(dev, "could not register media entity\n");
> +		goto free_ctrl;
> +	}
> +
> +	ov5645->sd.dev = &client->dev;
> +	ret = v4l2_async_register_subdev(&ov5645->sd);
> +	if (ret < 0) {
> +		dev_err(dev, "could not register v4l2 device\n");
> +		goto free_entity;
> +	}
> +
> +	return 0;
> +
> +free_entity:
> +	media_entity_cleanup(&ov5645->sd.entity);
> +free_ctrl:
> +	v4l2_ctrl_handler_free(&ov5645->ctrls);
> +
> +	return ret;
> +}
> +
> +
> +static int ov5645_remove(struct i2c_client *client)
> +{
> +	struct v4l2_subdev *sd = i2c_get_clientdata(client);
> +	struct ov5645 *ov5645 = to_ov5645(sd);
> +
> +	v4l2_async_unregister_subdev(&ov5645->sd);
> +	media_entity_cleanup(&ov5645->sd.entity);
> +	v4l2_ctrl_handler_free(&ov5645->ctrls);
> +
> +	return 0;
> +}
> +
> +
> +static const struct i2c_device_id ov5645_id[] = {
> +	{ "ov5645", 0 },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(i2c, ov5645_id);
> +
> +#if IS_ENABLED(CONFIG_OF)
> +static const struct of_device_id ov5645_of_match[] = {
> +	{ .compatible = "ovti,ov5645" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, ov5645_of_match);
> +#endif
> +
> +static struct i2c_driver ov5645_i2c_driver = {
> +	.driver = {
> +		.of_match_table = of_match_ptr(ov5645_of_match),
> +		.name  = "ov5645",
> +	},
> +	.probe  = ov5645_probe,
> +	.remove = ov5645_remove,
> +	.id_table = ov5645_id,
> +};
> +
> +module_i2c_driver(ov5645_i2c_driver);
> +
> +MODULE_DESCRIPTION("Omnivision OV5645 Camera Driver");
> +MODULE_AUTHOR("Todor Tomov <todor.tomov@linaro.org>");
> +MODULE_LICENSE("GPL v2");
> 

Regards,

	Hans