linux-kernel - Re: [PATCH] leds: pca963x: Fix open-drain initialization

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Message-ID: <20191118133031.GA90092@majorz.localdomain>
Date:   Mon, 18 Nov 2019 15:30:31 +0200
From:   Zahari Petkov <zahari@...ena.io>
To:     Pavel Machek <pavel@....cz>
Cc:     Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Dan Murphy <dmurphy@...com>, Zahari Petkov <zahari@...ena.io>,
        linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] leds: pca963x: Fix open-drain initialization

On Mon, Nov 04, 2019 at 10:09:53AM +0100, Pavel Machek wrote:
> On Mon 2019-10-14 15:36:04, Zahari Petkov wrote:
> > OUTDRV setting (bit 2) of Mode register 2 has a default value of 1.
> > During initialization when open-drain is used, instead of setting
> > OUTDRV to 0, the driver keeps it as 1. OUTDRV setting is now correctly
> > initialized to 0 when open-drain is used.
> > 
> > Additionally the BIT macro is used for improved readibility.
> 
> You change more than you describe in the changelog.

You are indeed correct. I will provide a more detailed and precise description.

> 
> > +++ b/drivers/leds/leds-pca963x.c
> > @@ -438,12 +438,12 @@ static int pca963x_probe(struct i2c_client *client,
> >  						    PCA963X_MODE2);
> >  		/* Configure output: open-drain or totem pole (push-pull) */
> >  		if (pdata->outdrv == PCA963X_OPEN_DRAIN)
> > -			mode2 |= 0x01;
> > +			mode2 &= ~BIT(2);
> 
> | 0 -> & ~0x04;
> 
> >  		else
> > -			mode2 |= 0x05;
> > +			mode2 |= BIT(2);
> 
> | 5 -> | 0x04;
> 
> Are you sure?

Yes, I need to explain this better in the updated description.

> 
> Additionaly, we already have defines for bits in mode2 register:
> 
> #define PCA963X_MODE2_DMBLNK    0x20    /* Enable blinking */
> 
> So if you care about readability, perhaps you should add defines for
> invert/ open drain there, and then use them?
> 
> Please keep using 0xab instead of BIT() for consistency with the rest
> of the driver.

I will update the code to use new defines instead of BIT().

Thanks a lot!
Zahari