linux-kernel - Re: [PATCH v4 1/2] hwmon: (adt7475) Added attenuator bypass support

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Date:   Wed, 22 Jan 2020 07:03:55 -0800
From:   Guenter Roeck <linux@...ck-us.net>
To:     Logan Shaw <logan.shaw@...iedtelesis.co.nz>, jdelvare@...e.com,
        robh+dt@...nel.org
Cc:     linux-hwmon@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, Joshua.Scott@...iedtelesis.co.nz,
        Chris.Packham@...iedtelesis.co.nz
Subject: Re: [PATCH v4 1/2] hwmon: (adt7475) Added attenuator bypass support

On 1/19/20 4:17 PM, Logan Shaw wrote:
> Added support for reading DTS properties to set attenuators on
> device probe for the ADT7473, ADT7475, ADT7476, and ADT7490.
> 
> Signed-off-by: Logan Shaw <logan.shaw@...iedtelesis.co.nz>
> ---
> ---
>   drivers/hwmon/adt7475.c | 76 +++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 76 insertions(+)
> 
> diff --git a/drivers/hwmon/adt7475.c b/drivers/hwmon/adt7475.c
> index 6c64d50c9aae..2bb787acb363 100644
> --- a/drivers/hwmon/adt7475.c
> +++ b/drivers/hwmon/adt7475.c
> @@ -19,6 +19,7 @@
>   #include <linux/hwmon-vid.h>
>   #include <linux/err.h>
>   #include <linux/jiffies.h>
> +#include <linux/of.h>
>   #include <linux/util_macros.h>
>   
>   /* Indexes for the sysfs hooks */
> @@ -1457,6 +1458,76 @@ static int adt7475_update_limits(struct i2c_client *client)
>   	return 0;
>   }
>   
> +/**

I don't see the point of adding this private comment into the documentation.

> + * Attempts to read a u32 property from the DTS, if there is no error and
> + * the properties value is zero then the bit given by parameter bit_index
> + * is cleared in the parameter config. If the value is non-zero then the bit
> + * is set.
> + *
> + * If reading the dts property returned an error code then it is returned and
> + * the config parameter is not modified.
> + */
> +static int modify_config_from_dts_prop(const struct i2c_client *client,
> +								char *dts_property, u8 *config, u8 bit_index) {

Alignment is far off. Please run "checkpatch --strict" and fix all problems
it reports.

total: 6 errors, 12 warnings, 9 checks, 94 lines checked

is a bit much.

modify_config_from_dts_prop and dts_property are unnecessary long and result
in multi-line code. Please use shorter function/parameter names.

> +	u32 is_attenuator_bypassed = 0;
> +	int ret = of_property_read_u32(client->dev.of_node, dts_property,
> +									&is_attenuator_bypassed);
> +
> +	if (! ret) {
> +			if (is_attenuator_bypassed)
> +		*config |= (1 << bit_index);
> +	else
> +		*config &= ~(1 << bit_index);
> +	}
> +
> +	return ret;

This return value is never used. Please drop it.

> +}
> +
> +/**
> + * Reads all individual voltage input bypass attenuator properties from the
> + * DTS, and if the property is present the corresponding bit is set in the
> + * register.
> +
> + * Properties are in the form of "bypass-attenuator-inx", where x is an
> + * integer from the set {0, 1, 3, 4} (can not bypass in2 attenuator).
> +.*
> + * The adt7473 and adt7475 only support bypassing in1.
> + *
> + * Returns a negative error code if there was an error writing to the register.
> + */
> +static int load_all_bypass_attenuators(const struct i2c_client *client,
> +					      int chip, u8 *config2, u8 *config4)
> +{
> +	u8 config2_copy = *config2;
> +	u8 config4_copy = *config4;
> +
Two "copy" variables are unnecessary, as only one is ever used.

> +	if (chip == adt7476 || chip == adt7490) {
> +		modify_config_from_dts_prop(client, "bypass-attenuator-in0",
> +									&config4_copy, 4);
> +		modify_config_from_dts_prop(client, "bypass-attenuator-in1",
> +									&config4_copy, 5);
> +		modify_config_from_dts_prop(client, "bypass-attenuator-in3",
> +									&config4_copy, 6);
> +		modify_config_from_dts_prop(client, "bypass-attenuator-in4",
> +									&config4_copy, 7);
> +
> +		if (i2c_smbus_write_byte_data(client, REG_CONFIG4, config4_copy) < 0)
> +			return -EREMOTEIO;
> +
> +		*config4 = config4_copy;
> +	} else if (chip == adt7473 || chip == adt7475) {
> +		modify_config_from_dts_prop(client, "bypass-attenuator-in1",
> +									&config2_copy, 5);
> +
> +		if (i2c_smbus_write_byte_data(client, REG_CONFIG2, config2_copy) < 0)
> +			return -EREMOTEIO;

Please do not override error codes.

> +
> +		*config2 = config2_copy;
> +	}
> +
> +	return 0;
> +}
> +
>   static int adt7475_probe(struct i2c_client *client,
>   			 const struct i2c_device_id *id)
>   {
> @@ -1546,6 +1617,11 @@ static int adt7475_probe(struct i2c_client *client,
>   
>   	/* Voltage attenuators can be bypassed, globally or individually */
>   	config2 = adt7475_read(REG_CONFIG2);
> +	if (load_all_bypass_attenuators(client, chip,
> +						&config2, &(data->config4)) < 0)
> +		dev_warn(&client->dev,
> +			 "Error setting bypass attenuator bits\n");
> +
>   	if (config2 & CONFIG2_ATTN) {
>   		data->bypass_attn = (0x3 << 3) | 0x3;
>   	} else {
>