Re: [PATCH v2 05/10] pwm: ntxec: Add driver for PWM function in Netronix EC

["Jonathan Neuschäfer" <j.neuschaefer@gmx.net>]

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On Sat, Sep 05, 2020 at 09:08:49PM +0300, Andy Shevchenko wrote:
> On Saturday, September 5, 2020, Jonathan Neuschäfer <j.neuschaefer@gmx.net>
> wrote:
> 
> > 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 Neuschäfer <j.neuschaefer@gmx.net>
> > ---
[...]
> > +#include <linux/of_device.h>
> 
> 
> 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)
> 
> 
> You spread this macro among the drivers w/o explanation what’s going 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 |= regmap_write(pwm->ec->regmap, NTXEC_REG_PERIOD_HIGH,
> > u8_to_reg(period >> 8));
> > +       res |= regmap_write(pwm->ec->regmap, NTXEC_REG_PERIOD_LOW,
> > u8_to_reg(period));
> > +       res |= regmap_write(pwm->ec->regmap, NTXEC_REG_DUTY_HIGH,
> > u8_to_reg(duty >> 8));
> > +       res |= regmap_write(pwm->ec->regmap, NTXEC_REG_DUTY_LOW,
> > u8_to_reg(duty));
> 
> 
> These funny res |= 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;
> 
> 
> What?!

That's an editing error, sorry.

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

Okay


Thanks for the review,
Jonathan Neuschäfer

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