linux-kernel - Re: [PATCH 4/6] regulator: Initial commit of sy7636a

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20210122133718.GB6391@sirena.org.uk>
Date:   Fri, 22 Jan 2021 13:37:18 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Alistair Francis <alistair23@...il.com>
Cc:     Alistair Francis <alistair@...stair23.me>, lee.jones@...aro.org,
        Rob Herring <robh+dt@...nel.org>, lgirdwood@...il.com,
        dl-linux-imx <linux-imx@....com>,
        Sascha Hauer <kernel@...gutronix.de>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/6] regulator: Initial commit of sy7636a

On Thu, Jan 21, 2021 at 10:24:10PM -0800, Alistair Francis wrote:
> On Mon, Jan 18, 2021 at 4:32 AM Mark Brown <broonie@...nel.org> wrote:
> > On Sat, Jan 16, 2021 at 08:25:37PM -0800, Alistair Francis wrote:

> > > +static int get_vcom_voltage_op(struct regulator_dev *rdev)
> > > +{
> > > +     int ret = get_vcom_voltage_mv(rdev->regmap);
> > > +

> > Why is this get_vcom_voltage_mv() function not in the regulator driver,
> > and why is it not just inline here?  It also needs namespacing.

> I'm not sure what you mean, can you please explain?

This is a wrapper for a function that has exactly one caller but is not
only a separate function but also in the MFD header, part of a separate
driver.  This seems at best pointless.

> > Why do you need this delay here, and what purpose is this lock intended

> The delay is to allow a power ramp up, I have added a comment.

Use the standard ramp_delay, don't open code it.

> > > +static int sy7636a_regulator_suspend(struct device *dev)
> > > +{
> > > +     int ret;
> > > +     struct sy7636a *sy7636a = dev_get_drvdata(dev->parent);
> > > +
> > > +     ret = get_vcom_voltage_mv(sy7636a->regmap);
> > > +
> > > +     if (ret > 0)
> > > +             sy7636a->vcom = (unsigned int)ret;
> > > +
> > > +     return 0;
> > > +}

> > What's going on here, and if you are going to store this value over
> > suspend why not store it in a variable of the correct type?  In general

> It is part of the vendor's kernel, they specifically added it to
> ensure vcom is set on resume.

"I copied this from the vendor" isn't really a great explanation...  If
the device is likely to get completely powered off and loosing settings
then presumably the entire register map, not just this one value, needs
to be saved and restored instead of just this one value.  If that is the
case it's probably best to use a register cache and just resync it on
resume.

Download attachment "signature.asc" of type "application/pgp-signature" (489 bytes)