linux-kernel - Re: [PATCH v2 2/2] hwmon: pmbus: Add ltc4286 driver

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Message-ID: <e223764a-c081-4634-810b-56886a29804a@roeck-us.net>
Date:   Tue, 31 Oct 2023 06:47:04 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Delphine_CC_Chiu/WYHQ/Wiwynn <Delphine_CC_Chiu@...ynn.com>,
        "patrick@...cx.xyz" <patrick@...cx.xyz>,
        Jean Delvare <jdelvare@...e.com>,
        Jonathan Corbet <corbet@....net>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] hwmon: pmbus: Add ltc4286 driver

On 10/30/23 23:46, Delphine_CC_Chiu/WYHQ/Wiwynn wrote:
[ ... ]
>>
>>> +
>>> +     ret = of_property_read_u32(client->dev.of_node,
>>> +                                "shunt-resistor-micro-ohms",
>> &rsense);
>>> +     if (ret < 0)
>>> +             return ret;
>>> +
>>> +     if (rsense == 0)
>>> +             return -EINVAL;
>>> +
>>> +     info = &ltc4286_info;
>>> +
>>> +     /* Default of VRANGE_SELECT = 1, 102.4V */
>>> +     if (device_property_read_bool(&client->dev,
>> "adi,vrange-select-25p6")) {
>>
>> What if the adi,vrange-select-25p6 property is not provided, but the chip
>> is programmed for this range ?
> The binding document tells programmers how to fill the dts.
> Thus, programmers must fill this property if their system is 25.6 volts voltage range.
> 

Sure, but there is no else case, meaning VRANGE_SELECT is
unmodified in that case. There is no guarantee that the chip
is in its power-on state.

Guenter