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

Guenter Roeck
2020-01-22T15:04:00Z

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@alliedtelesis.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 {
>