Re: [PATCH v4 2/3] hwmon: ltc4283: Add support for the LTC4283 Swap Controller

[Guenter Roeck <linux@roeck-us.net>]

On 12/12/25 08:50, Nuno Sá wrote:
> On Thu, 2025-12-11 at 09:56 -0800, Guenter Roeck wrote:
>> On 12/4/25 08:15, Nuno Sá via B4 Relay wrote:
>>> From: Nuno Sá <nuno.sa@analog.com>
>>>
>>> Support the LTC4283 How Swap Controller. The device features programmable
>>> current limit with foldback and independently adjustable inrush current to
>>> optimize the MOSFET safe operating area (SOA). The SOA timer limits MOSFET
>>> temperature rise for reliable protection against overstresses.
>>>
>>> An I2C interface and onboard ADC allow monitoring of board current,
>>> voltage, power, energy, and fault status.
>>>
>>> Signed-off-by: Nuno Sá <nuno.sa@analog.com>
>>> ---
>> ...
>>> diff --git a/drivers/hwmon/ltc4283.c b/drivers/hwmon/ltc4283.c
>>> new file mode 100644
>>> index 000000000000..d79432678b84
>>> --- /dev/null
>>> +++ b/drivers/hwmon/ltc4283.c
>> ...
>>> +
>>> +static int ltc4283_read_voltage_word(const struct ltc4283_hwmon *st,
>>> +				     u32 reg, u32 fs, long *val)
>>> +{
>>> +	__be16 in;
>>> +	int ret;
>>> +
>>> +	ret = regmap_bulk_read(st->map, reg, &in, sizeof(in));
>>
>> I had a look into the regmap code. In its current implementation,
>> that will work as long as
>> 1) regmap is configured to not cache anything
>> 2) the I2C controller supports I2C_FUNC_SMBUS_I2C_BLOCK
>>
> 
> Possibly dumb question... what would be the issue about doing multiple
> regmap reads if we can't do the bulk? That would be my naive approach in
> the driver if I'm not going to use the bulk API.
> 

You mean on the same address ? I don't have the chip to check, but I am quite
sure that it would return the 1st byte again.

FWIW, in the lm92 driver I used a regmap_bus to solve pretty much the same
problem.

Guenter