linux-kernel - RE: [PATCH v2 2/2] eeprom: at24: Add support for address-width property

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Message-ID: <0772C36F3434E145A062D024A4869A09010AA12F@PGSMSX101.gar.corp.intel.com>
Date:   Tue, 26 Jun 2018 07:11:54 +0000
From:   "Chiang, AlanX" <alanx.chiang@...el.com>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
CC:     "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "Yeh, Andy" <andy.yeh@...el.com>,
        "Shevchenko, Andriy" <andriy.shevchenko@...el.com>,
        "Mani, Rajmohan" <rajmohan.mani@...el.com>,
        "andy.shevchenko@...il.com" <andy.shevchenko@...il.com>,
        "brgl@...ev.pl" <brgl@...ev.pl>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "arnd@...db.de" <arnd@...db.de>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 2/2] eeprom: at24: Add support for address-width
 property

Hi Sakari,

> -----Original Message-----
> From: Sakari Ailus [mailto:sakari.ailus@...ux.intel.com]
> Sent: Tuesday, June 26, 2018 2:48 PM
> To: Chiang, AlanX <alanx.chiang@...el.com>
> Cc: linux-i2c@...r.kernel.org; Yeh, Andy <andy.yeh@...el.com>;
> Shevchenko, Andriy <andriy.shevchenko@...el.com>; Mani, Rajmohan
> <rajmohan.mani@...el.com>; andy.shevchenko@...il.com; brgl@...ev.pl;
> robh+dt@...nel.org; mark.rutland@....com; arnd@...db.de;
> gregkh@...uxfoundation.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH v2 2/2] eeprom: at24: Add support for address-width
> property
> 
> Hi Alan,
> 
> On Tue, Jun 26, 2018 at 02:22:08PM +0800, alanx.chiang@...el.com wrote:
> > From: "alanx.chiang" <alanx.chiang@...el.com>
> >
> > Provide a flexible way to determine the addressing bits of eeprom.
> > Pass the addressing bits to driver through address-width property.
> >
> > Signed-off-by: Alan Chiang <alanx.chiang@...el.com>
> > Signed-off-by: Andy Yeh <andy.yeh@...el.com>
> >
> > ---
> > since v1
> > -- Add a warn message for 8-bit addressing.
> >
> > ---
> >  drivers/misc/eeprom/at24.c | 16 ++++++++++++++++
> >  1 file changed, 16 insertions(+)
> >
> > diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> > index 0c125f2..231afcd 100644
> > --- a/drivers/misc/eeprom/at24.c
> > +++ b/drivers/misc/eeprom/at24.c
> > @@ -478,6 +478,22 @@ static void at24_properties_to_pdata(struct device
> *dev,
> >  	if (device_property_present(dev, "no-read-rollover"))
> >  		chip->flags |= AT24_FLAG_NO_RDROL;
> >
> > +	err = device_property_read_u32(dev, "address-width", &val);
> > +	if (!err) {
> > +		switch (val) {
> > +		case 8:
> > +			chip->flags &= ~AT24_FLAG_ADDR16;
> > +			dev_warn(dev, "address-width is 8, clear the ADD16
> bit\n");
> 
> Even though the default is 8 address bits, I don't see a need to issue a
> warning if the address-width property sets that to 8 explicitly. I.e. only warn
> if the flag was set.
> 

Do you mean I have to add a statement for checking if the bit has been set before?
For example:

If (chip->flags & AT24_FLAG_ADDR16)
	dev_warn(dev, "address-width is 8, clear the ADD16 bit\n");

If it is, I would like to modify it as below:

case 8:
	If (chip->flags & AT24_FLAG_ADDR16) {
		chip->flags &= ~AT24_FLAG_ADDR16;
		dev_warn(dev, "address-width is 8, clear the ADDR16 bit\n");
	}
	break;

> > +			break;
> > +		case 16:
> > +			chip->flags |= AT24_FLAG_ADDR16;
> > +			break;
> > +		default:
> > +			dev_warn(dev, "Bad \"address-width\" property:
> %u\n",
> > +				 val);
> > +		}
> > +	}
> > +
> >  	err = device_property_read_u32(dev, "size", &val);
> >  	if (!err)
> >  		chip->byte_len = val;
> 
> --
> Regards,
> 
> Sakari Ailus
> sakari.ailus@...ux.intel.com