linux-kernel - Re: [PATCH 2/2] hwmon: (pmbus): Add driver for BluTek BPA-RS600

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Date:   Tue, 16 Mar 2021 04:21:56 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     Guenter Roeck <linux@...ck-us.net>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "jdelvare@...e.com" <jdelvare@...e.com>
CC:     "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] hwmon: (pmbus): Add driver for BluTek BPA-RS600


On 16/03/21 4:43 pm, Guenter Roeck wrote:
> On 3/15/21 7:35 PM, Chris Packham wrote:
>> The BPA-RS600 is a compact 600W AC to DC removable power supply module.
>>
>> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
>> ---
<snip>
>> +
>> +static int bpa_rs600_read_word_data(struct i2c_client *client, int page,
>> +		int phase, int reg)+{
>> +	int ret;
>> +
>> +	if (page > 0)
>> +		return -ENXIO;
>> +
>> +	switch (reg) {
>> +	case PMBUS_VIN_UV_FAULT_LIMIT:
>> +	case PMBUS_VIN_OV_FAULT_LIMIT:
>> +	case PMBUS_VOUT_UV_FAULT_LIMIT:
>> +	case PMBUS_VOUT_OV_FAULT_LIMIT:
>> +		ret = -ENXIO;
> Is that needed ? Why not -ENODATA ?

Basically these commands get responses on the bus but they don't have 
valid data (nor are they documented in the datasheet). I'll add a 
comment to that effect.

If I'm reading things correctly -ENODATA is a signal to 
_pmbus_read_word_data use the "normal" read operation. So I need to 
return something other than that. I found another driver (mp2975.c) 
doing the same thing for what I assume are similar reasons so I went 
with -ENXIO.

>
>> +		break;
<snip>
> +
>> +static const struct i2c_device_id bpa_rs600_id[] = {
>> +	{ "bpa_rs600", 0 },
> Hmm, no, this has an underscore. Guess you'll have to use the trick from
> iio_hwmon.c or similar to generate a valid name.
>
> Oh, wait, this is a pmbus driver, and the pmbus core uses client->name.
> Maybe we need to add an optional strreplace() to the pmbus core.
Looking into this now.