linux-kernel - Re: [PATCH v3 1/3] hwmon: (mcp3021) add devicetree support

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Message-ID: <20161109193206.GB22665@roeck-us.net>
Date:   Wed, 9 Nov 2016 11:32:06 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Clemens Gruber <clemens.gruber@...ruber.com>
Cc:     linux-hwmon@...r.kernel.org, Jean Delvare <jdelvare@...e.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/3] hwmon: (mcp3021) add devicetree support

On Wed, Nov 09, 2016 at 06:16:13PM +0100, Clemens Gruber wrote:
> Support setting the reference voltage from the device tree.
> 
> Signed-off-by: Clemens Gruber <clemens.gruber@...ruber.com>
> ---
>  drivers/hwmon/mcp3021.c | 46 ++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 36 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/hwmon/mcp3021.c b/drivers/hwmon/mcp3021.c
> index 972444a..81f4b7f 100644
> --- a/drivers/hwmon/mcp3021.c
> +++ b/drivers/hwmon/mcp3021.c
> @@ -4,6 +4,7 @@
>   * Copyright (C) 2008-2009, 2012 Freescale Semiconductor, Inc.
>   * Author: Mingkai Hu <Mingkai.hu@...escale.com>
>   * Reworked by Sven Schuchmann <schuchmann@...leissheimer.de>
> + * Copyright (C) 2016 Clemens Gruber <clemens.gruber@...ruber.com>

Sorry, I can't accept that for such a minor change. Feel free to add
something like "devicetree support added by ...", if you like.

>   *
>   * This driver export the value of analog input voltage to sysfs, the
>   * voltage unit is mV. Through the sysfs interface, lm-sensors tool
> @@ -22,11 +23,13 @@
>  #include <linux/i2c.h>
>  #include <linux/err.h>
>  #include <linux/device.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
>  
> -/* Vdd info */
> +/* Vdd / reference voltage in millivolt */
>  #define MCP3021_VDD_MAX		5500
>  #define MCP3021_VDD_MIN		2700
> -#define MCP3021_VDD_REF		3300
> +#define MCP3021_VDD_DEFAULT	3300

I don't really see the value of changing this, but if it makes you
feel better at least make it MCP3021_VDD_REF_DEFAULT.

>  
>  /* output format */
>  #define MCP3021_SAR_SHIFT	2
> @@ -47,7 +50,7 @@ enum chips {
>   */
>  struct mcp3021_data {
>  	struct device *hwmon_dev;
> -	u32 vdd;	/* device power supply */
> +	u32 vdd;        /* supply and reference voltage in millivolt */
>  	u16 sar_shift;
>  	u16 sar_mask;
>  	u8 output_res;
> @@ -106,6 +109,7 @@ static int mcp3021_probe(struct i2c_client *client,
>  {
>  	int err;
>  	struct mcp3021_data *data = NULL;
> +	struct device_node *np = client->dev.of_node;
>  
>  	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
>  		return -ENODEV;
> @@ -117,6 +121,21 @@ static int mcp3021_probe(struct i2c_client *client,
>  
>  	i2c_set_clientdata(client, data);
>  
> +	if (np) {
> +		if (of_property_read_u32(np, "reference-voltage-microvolt",
> +					 &data->vdd))
> +			data->vdd = MCP3021_VDD_DEFAULT;
> +		else
> +			data->vdd /= 1000;

It would be slightly better to reverse the logic here to make the code easier
to read.

		if (!of_property_read_u32(np, "reference-voltage-microvolt",
					  &data->vdd))
			data->vdd /= 1000;
		else
			data->vdd = MCP3021_VDD_DEFAULT;

Not worth arguing about it, though, so feel free to keep it as is.

> +	} else {
> +		u32 *pdata = dev_get_platdata(&client->dev);
> +
> +		if (pdata)
> +			data->vdd = *pdata;
> +		else
> +			data->vdd = MCP3021_VDD_DEFAULT;
> +	}
> +
>  	switch (id->driver_data) {
>  	case mcp3021:
>  		data->sar_shift = MCP3021_SAR_SHIFT;
> @@ -129,15 +148,12 @@ static int mcp3021_probe(struct i2c_client *client,
>  		data->sar_mask = MCP3221_SAR_MASK;
>  		data->output_res = MCP3221_OUTPUT_RES;
>  		break;
> +	default:
> +		return -ENODEV;

Hmm ... that is really an unrelated change (nor is it really needed
unless there is a bug in the code). Not worth arguing about it either,
but please keep in mind that this is one of the things making life
hard for maintainers.

>  	}
>  
> -	if (dev_get_platdata(&client->dev)) {
> -		data->vdd = *(u32 *)dev_get_platdata(&client->dev);
> -		if (data->vdd > MCP3021_VDD_MAX || data->vdd < MCP3021_VDD_MIN)
> -			return -EINVAL;
> -	} else {
> -		data->vdd = MCP3021_VDD_REF;
> -	}
> +	if (data->vdd > MCP3021_VDD_MAX || data->vdd < MCP3021_VDD_MIN)
> +		return -EINVAL;
>  
>  	err = sysfs_create_file(&client->dev.kobj, &dev_attr_in0_input.attr);
>  	if (err)
> @@ -173,9 +189,19 @@ static const struct i2c_device_id mcp3021_id[] = {
>  };
>  MODULE_DEVICE_TABLE(i2c, mcp3021_id);
>  
> +#ifdef CONFIG_OF
> +static const struct of_device_id of_mcp3021_match[] = {
> +	{ .compatible = "microchip,mcp3021", .data = (void *)mcp3021 },
> +	{ .compatible = "microchip,mcp3221", .data = (void *)mcp3221 },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, of_mcp3021_match);
> +#endif
> +
>  static struct i2c_driver mcp3021_driver = {
>  	.driver = {
>  		.name = "mcp3021",
> +		.of_match_table = of_match_ptr(of_mcp3021_match),
>  	},
>  	.probe = mcp3021_probe,
>  	.remove = mcp3021_remove,
> -- 
> 2.10.2
>