linux-kernel - Re: [PATCH v1 1/2] leds: rt4505: Add support for Richtek RT4505 flash led controller

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Date:   Tue, 27 Oct 2020 18:06:21 +0800
From:   ChiYuan Huang <u0084500@...il.com>
To:     Pavel Machek <pavel@....cz>
Cc:     dmurphy@...com, robh+dt@...nel.org, linux-leds@...r.kernel.org,
        lkml <linux-kernel@...r.kernel.org>,
        cy_huang <cy_huang@...htek.com>, devicetree@...r.kernel.org
Subject: Re: [PATCH v1 1/2] leds: rt4505: Add support for Richtek RT4505 flash
 led controller

Hi, Parvel:
  Continue the last mail, I'm confused about the rule 80-characters-per-line.
I check some information about submitting changes.
https://www.phoronix.com/scan.php?page=news_item&px=Linux-Kernel-Deprecates-80-Col
Could you help to explain the current rule about this limit? still 80
characters per line? or it has been changed to 100.

ChiYuan Huang <u0084500@...il.com> 於 2020年10月27日 週二 下午5:27寫道：
>
> Pavel Machek <pavel@....cz> 於 2020年10月27日 週二 下午4:29寫道：
> >
> > Hi!
> >
> > > From: ChiYuan Huang <cy_huang@...htek.com>
> > >
> > > Add support for RT4505 flash led controller. It can support up to 1.5A
> > > flash current with hardware timeout and low input voltage
> > > protection.
> >
> > Please use upper-case "LED" everywhere.
> >
> > This should be 2nd in the series, after DT changes.
> Sure, will ack in next series patch.
> >
> > > Signed-off-by: ChiYuan Huang <cy_huang@...htek.com>
> > > ---
> > >  drivers/leds/Kconfig       |  11 ++
> > >  drivers/leds/Makefile      |   1 +
> > >  drivers/leds/leds-rt4505.c | 397 +++++++++++++++++++++++++++++++++++++++++++++
> > >  3 files changed, 409 insertions(+)
> > >  create mode 100644 drivers/leds/leds-rt4505.c
> >
> > Lets put this into drivers/leds/flash/. (Yes, you'll have to create
> > it).
> OK
> >
> >
> > > +     help
> > > +       This option enables support for the RT4505 flash led controller.
> >
> > Information where it is used would be welcome here.
> How about to add the below line for the extra information?
> Usually used to company with the camera device on smartphone/tablet products
> >
> > > +       It can support up to 1.5A flash strobe current with hardware timeout
> > > +       and low input voltage protection.
> >
> > This does not / should not be here.
> OK
> > > +
> > > +static int rt4505_torch_brightness_set(struct led_classdev *lcdev, enum led_brightness level)
> > > +{
> >
> > 80 columns, where easy.
> I'll review all source code to meet the 80 column limit.
> >
> > > +     struct rt4505_priv *priv = container_of(lcdev, struct rt4505_priv, flash.led_cdev);
> > > +     u32 val = 0;
> > > +     int ret;
> > > +
> > > +     mutex_lock(&priv->lock);
> > > +
> > > +     if (level != LED_OFF) {
> > > +             ret = regmap_update_bits(priv->regmap, RT4505_REG_ILED, RT4505_ITORCH_MASK,
> > > +                                      (level - 1) << RT4505_ITORCH_SHIFT);
> > > +             if (ret)
> > > +                     goto unlock;
> > > +
> > > +             val = RT4505_TORCH_SET;
> > > +     }
> > > +
> > > +     ret = regmap_update_bits(priv->regmap, RT4505_REG_ENABLE, RT4505_ENABLE_MASK, val);
> > > +
> > > +unlock:
> > > +     mutex_unlock(&priv->lock);
> > > +     return ret;
> > > +}
> >
> > Why is the locking needed? What will the /sys/class/leds interface
> > look like on system with your flash?
>
> The original thought is because there's still another way to control
> flash like as v4l2.
> But after reviewing the source code, led sysfs node will be protected
> by led_cdev->led_access.
> And V4L2 flash will also be protected by v4l2_fh_is_singular API.
> I think the whole locking in the source code code may be removed. Right?
> >
> > > +static int rt4505_flash_strobe_get(struct led_classdev_flash *fled_cdev, bool *state)
> > > +{
> > > +     struct rt4505_priv *priv = container_of(fled_cdev, struct rt4505_priv, flash);
> > > +     u32 val;
> > > +     int ret;
> > > +
> > > +     mutex_lock(&priv->lock);
> > > +
> > > +     ret = regmap_read(priv->regmap, RT4505_REG_ENABLE, &val);
> > > +     if (ret)
> > > +             goto unlock;
> > > +
> > > +     *state = ((val & RT4505_FLASH_GET) == RT4505_FLASH_GET) ? true : false;
> >
> > No need for ? ... part.
> Do you mean this function is not needed? If yes, it can be removed.
> But if it removed, led sysfs flash_strobe show will be not supported.
> >
> > > +static bool rt4505_is_accessible_reg(struct device *dev, unsigned int reg)
> > > +{
> > > +     if (reg == RT4505_REG_RESET || (reg >= RT4505_REG_CONFIG  && reg <= RT4505_REG_FLAGS))
> > > +             return true;
> >
> > Make this two stagements.
> Like as the below one?? Or separate it into two if case.
> if (reg == RT4505_REG_RESET ||
>        reg >= RT4505_REG_CONFIG  && reg <= RT4505_REG_FLAGS))
> >
> > Otherwise... looks like easy simple driver, thanks.
> >
> > Best regards,
> >                                                                 Pavel
> > --
> > http://www.livejournal.com/~pavelmachek