linux-kernel - Re: [PATCH 1/5] hwmon: (pmbus/pim4328) Add function for reading direct mode coefficients

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Date:   Wed, 19 May 2021 16:38:25 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Erik Rosen <erik.rosen@...ormote.com>,
        Jean Delvare <jdelvare@...e.com>,
        Jonathan Corbet <corbet@....net>, linux-hwmon@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] hwmon: (pmbus/pim4328) Add function for reading
 direct mode coefficients

On 5/19/21 1:10 PM, Erik Rosen wrote:
> Add the function pmbus_read_coefficients to pmbus_core to be able to
> read and decode the coefficients for the direct format for a certain
> command and read/write direction.
> 
> Signed-off-by: Erik Rosen <erik.rosen@...ormote.com>
> ---
>   drivers/hwmon/pmbus/pmbus.h      |  4 ++++
>   drivers/hwmon/pmbus/pmbus_core.c | 38 ++++++++++++++++++++++++++++++++
>   2 files changed, 42 insertions(+)
> 
> diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
> index 3968924f8533..a131b253ebf9 100644
> --- a/drivers/hwmon/pmbus/pmbus.h
> +++ b/drivers/hwmon/pmbus/pmbus.h
> @@ -499,6 +499,10 @@ int pmbus_get_fan_rate_cached(struct i2c_client *client, int page, int id,
>   			      enum pmbus_fan_mode mode);
>   int pmbus_update_fan(struct i2c_client *client, int page, int id,
>   		     u8 config, u8 mask, u16 command);
> +int pmbus_read_coefficients(struct i2c_client *client,
> +			    struct pmbus_driver_info *info,
> +			    enum pmbus_sensor_classes sensor_class,
> +			    u8 command, bool for_reading);
>   struct dentry *pmbus_get_debugfs_dir(struct i2c_client *client);
>   
>   #endif /* PMBUS_H */
> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
> index bbd745178147..14d3d3352aac 100644
> --- a/drivers/hwmon/pmbus/pmbus_core.c
> +++ b/drivers/hwmon/pmbus/pmbus_core.c
> @@ -301,6 +301,44 @@ int pmbus_update_fan(struct i2c_client *client, int page, int id,
>   }
>   EXPORT_SYMBOL_NS_GPL(pmbus_update_fan, PMBUS);
>   
> +/*
> + * Read the coefficients for direct mode.
> + */
> +int pmbus_read_coefficients(struct i2c_client *client,
> +			    struct pmbus_driver_info *info,
> +			    enum pmbus_sensor_classes sensor_class,
> +			    u8 command, bool for_reading)
> +{

The way the code is written, we never need to read coefficients for writing.
With that in mind, I don't think the 'for_reading' parameter is necessary.

Guenter

> +	int rv;
> +	union i2c_smbus_data data;
> +	s8 R;
> +	s16 m, b;
> +
> +	data.block[0] = 2;
> +	data.block[1] = command;
> +	data.block[2] = for_reading ? 0x01 : 0x00;
> +
> +	rv = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
> +			    I2C_SMBUS_WRITE, PMBUS_COEFFICIENTS,
> +			    I2C_SMBUS_BLOCK_PROC_CALL, &data);
> +
> +	if (rv < 0)
> +		return rv;
> +
> +	if (data.block[0] != 5)
> +		return -EIO;
> +
> +	m = data.block[1] | (data.block[2] << 8);
> +	b = data.block[3] | (data.block[4] << 8);
> +	R = data.block[5];
> +	info->m[sensor_class] = m;
> +	info->b[sensor_class] = b;
> +	info->R[sensor_class] = R;
> +
> +	return rv;
> +}
> +EXPORT_SYMBOL_GPL(pmbus_read_coefficients);

EXPORT_SYMBOL_NS_GPL(pmbus_read_coefficients, PMBUS);

> +
>   int pmbus_read_word_data(struct i2c_client *client, int page, int phase, u8 reg)
>   {
>   	int rv;
>