linux-kernel - Re: [PATCH] hwmon: (max77705) add initial support

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Message-ID: <CABTCjFD8yozABXGVMtxhHTkpkAVis6tR=LEN9jNpvurTe_0iyQ@mail.gmail.com>
Date: Tue, 4 Mar 2025 13:03:14 +0300
From: Dzmitry Sankouski <dsankouski@...il.com>
To: Guenter Roeck <linux@...ck-us.net>
Cc: 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] hwmon: (max77705) add initial support

ср, 26 февр. 2025 г. в 16:53, Guenter Roeck <linux@...ck-us.net>:
>
> On 2/25/25 11:11, Dzmitry Sankouski wrote:
> > Add support for max77705 hwmon. Includes charger input, system bus, and
> > vbyp measurements.
> >
> > Signed-off-by: Dzmitry Sankouski <dsankouski@...il.com>
> > ---
> > Maxim MAX77705 is a Companion Power Management and Type-C interface IC.
> > It includes charger and fuel gauge blocks, and is capable of measuring
> > charger input current, system bus volatage and current, and bypass
> > voltage.
> >
> > This patch add support for mentioned measurements.
(...)
> > +
> > +struct channel_desc {
> > +     u8 reg;
> > +     u8 avg_reg;
> > +     const char *const label;
> > +     // register resolution. nano Volts for voltage, nano Amperes for current
> > +     u64 resolution;
>
> Why u64 ?
>

Resolution is in nano Volts, and VBYP value is typically 5v, which leads to
u32 overflow.

(...)
>
> This is unusual for an mfd driver. Why not pass regmap from the parent
> driver ?
>

This limits access to shared device register map by using readable table
with related registers only.

(...)

-- 
Best regards and thanks for review,
Dzmitry