linux-kernel - Re: [PATCHv3] support for AD5820 camera auto-focus coil

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Date:	Tue, 24 May 2016 12:16:40 +0300
From:	Ivaylo Dimitrov <ivo.g.dimitrov.75@...il.com>
To:	Pavel Machek <pavel@....cz>
Cc:	pali.rohar@...il.com, sre@...nel.org,
	kernel list <linux-kernel@...r.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-omap@...r.kernel.org, tony@...mide.com, khilman@...nel.org,
	aaro.koskinen@....fi, patrikbachan@...il.com, serge@...lyn.com,
	linux-media@...r.kernel.org, mchehab@....samsung.com,
	sakari.ailus@....fi
Subject: Re: [PATCHv3] support for AD5820 camera auto-focus coil



On 24.05.2016 12:04, Pavel Machek wrote:
> Hi!
>
>>> +static int ad5820_registered(struct v4l2_subdev *subdev)
>>> +{
>>> +	struct ad5820_device *coil = to_ad5820_device(subdev);
>>> +	struct i2c_client *client = v4l2_get_subdevdata(subdev);
>>> +
>>> +	coil->vana = regulator_get(&client->dev, "VANA");
>>
>> devm_regulator_get()?
>
> I'd rather avoid devm_ here. Driver is simple enough to allow it.
>

Now thinking about it, what would happen here if regulator_get() returns 
-EPROBE_DEFER? Wouldn't it be better to move regulator_get to the 
probe() function, something like:

static int ad5820_probe(struct i2c_client *client,
			const struct i2c_device_id *devid)
{
	struct ad5820_device *coil;
	int ret = 0;

	coil = devm_kzalloc(sizeof(*coil), GFP_KERNEL);
	if (coil == NULL)
		return -ENOMEM;

	coil->vana = devm_regulator_get(&client->dev, NULL);
	if (IS_ERR(coil->vana)) {
		ret = PTR_ERR(coil->vana);
		if (ret != -EPROBE_DEFER)
			dev_err(&client->dev, "could not get regulator for vana\n");
		return ret;
	}

	mutex_init(&coil->power_lock);
...

with the appropriate changes to remove() because of the devm API usage.

>>> +#define AD5820_RAMP_MODE_LINEAR		(0 << 3)
>>> +#define AD5820_RAMP_MODE_64_16		(1 << 3)
>>> +
>>> +struct ad5820_platform_data {
>>> +	int (*set_xshutdown)(struct v4l2_subdev *subdev, int set);
>>> +};
>>> +
>>> +#define to_ad5820_device(sd)	container_of(sd, struct ad5820_device, subdev)
>>> +
>>> +struct ad5820_device {
>>> +	struct v4l2_subdev subdev;
>>> +	struct ad5820_platform_data *platform_data;
>>> +	struct regulator *vana;
>>> +
>>> +	struct v4l2_ctrl_handler ctrls;
>>> +	u32 focus_absolute;
>>> +	u32 focus_ramp_time;
>>> +	u32 focus_ramp_mode;
>>> +
>>> +	struct mutex power_lock;
>>> +	int power_count;
>>> +
>>> +	int standby : 1;
>>> +};
>>> +
>>
>> The same for struct ad5820_device, is it really part of the public API?
>
> Let me check what can be done with it.
> 									Pavel
>