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Date:   Thu, 10 Sep 2020 21:09:57 +0200
From:   Jonathan =?utf-8?Q?Neusch=C3=A4fer?= <j.neuschaefer@gmx.net>
To:     Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     Jonathan =?utf-8?Q?Neusch=C3=A4fer?= <j.neuschaefer@gmx.net>,
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        Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= 
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Subject: Re: [PATCH v2 05/10] pwm: ntxec: Add driver for PWM function in
 Netronix EC
Message-ID: <20200910190957.GB3306@latitude>
References: <20200905133230.1014581-1-j.neuschaefer@gmx.net>
 <20200905133230.1014581-6-j.neuschaefer@gmx.net>
 <CAHp75VdUHoOyM3bObzhdfiqpne0AmSK_UakteTZxnjqJVrNV9A@mail.gmail.com>
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On Sat, Sep 05, 2020 at 09:08:49PM +0300, Andy Shevchenko wrote:
> On Saturday, September 5, 2020, Jonathan Neusch=C3=A4fer <j.neuschaefer@g=
mx.net>
> wrote:
>=20
> > The Netronix EC provides a PWM output which is used for the backlight
> > on some ebook readers. This patches adds a driver for the PWM output.
> >
> > Signed-off-by: Jonathan Neusch=C3=A4fer <j.neuschaefer@gmx.net>
> > ---
[...]
> > +#include <linux/of_device.h>
>=20
>=20
> mod_devicetable.h

Okay

> > +/* Convert an 8-bit value into the correct format for writing into a
> > register */
> > +#define u8_to_reg(x) (((x) & 0xff) << 8)
>=20
>=20
> You spread this macro among the drivers w/o explanation what=E2=80=99s go=
ing on. I
> think there will be better approach.

Okay, I'll move it to ntxec.h and expand on the explanation. I think
what's missing is the following part:

  Some registers, such as the battery status register (0x41), are in
  big-endian, but others only have eight significant bits, which are in
  the first byte transmitted over I2C (the MSB of the big-endian value).
  This convenience macro/function converts an 8-bit value to 16-bit for
  use in the second kind of register.

> > +
> > +       res |=3D regmap_write(pwm->ec->regmap, NTXEC_REG_PERIOD_HIGH,
> > u8_to_reg(period >> 8));
> > +       res |=3D regmap_write(pwm->ec->regmap, NTXEC_REG_PERIOD_LOW,
> > u8_to_reg(period));
> > +       res |=3D regmap_write(pwm->ec->regmap, NTXEC_REG_DUTY_HIGH,
> > u8_to_reg(duty >> 8));
> > +       res |=3D regmap_write(pwm->ec->regmap, NTXEC_REG_DUTY_LOW,
> > u8_to_reg(duty));
>=20
>=20
> These funny res |=3D is unusual pattern for returned error codes. Moreover
> you are shadowing the real ones. Same go the rest drovers. Please fix by
> checking each separately.

Okay

> > +       platform_set_drvdata(pdev, pwm);
> > +
> > +       return (res < 0) ? -EIO : 0;
>=20
>=20
> What?!

That's an editing error, sorry.

> > +static const struct of_device_id ntxec_pwm_of_match[] =3D {
> > +       { .compatible =3D "netronix,ntxec-pwm" },
> >
> >
>=20
> > +       { },
>=20
>=20
> No comma.

Okay


Thanks for the review,
Jonathan Neusch=C3=A4fer

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