linux-kernel - Re: [PATCH v2 2/2] rtc: nuvoton: Compatible with NCT3015Y-R and NCT3018Y-R

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Message-ID: <202308091936514bb18c4e@mail.local>
Date:   Wed, 9 Aug 2023 21:36:51 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Mia Lin <mimi05633@...il.com>, avifishman70@...il.com,
        tmaimon77@...il.com, tali.perry1@...il.com, venture@...gle.com,
        yuenn@...gle.com, benjaminfair@...gle.com, a.zummo@...ertech.it,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, KWLIU@...oton.com, JJLIU0@...oton.com,
        KFLIN@...oton.com, mylin1@...oton.com, openbmc@...ts.ozlabs.org,
        linux-rtc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] rtc: nuvoton: Compatible with NCT3015Y-R and
 NCT3018Y-R

On 09/08/2023 16:29:33+0200, Krzysztof Kozlowski wrote:
> On 09/08/2023 11:51, Mia Lin wrote:
> > -	flags = NCT3018Y_BIT_TWO;
> > -	err = i2c_smbus_write_byte_data(client, NCT3018Y_REG_CTRL, flags);
> > -	if (err < 0) {
> > -		dev_dbg(&client->dev, "Unable to write NCT3018Y_REG_CTRL\n");
> > -		return err;
> > +	flags = i2c_smbus_read_byte_data(client, NCT3018Y_REG_PART);
> > +	if (flags < 0) {
> > +		dev_dbg(&client->dev, "%s: read error\n", __func__);
> > +		return flags;
> > +	} else if (flags & NCT3018Y_REG_PART_NCT3018Y) {
> > +		if (!(flags & data->part_number))
> > +			dev_warn(&client->dev, "%s: part_num=0x%x but NCT3018Y_REG_PART=0x%x\n",
> > +				 __func__, data->part_number, flags);
> > +		flags = NCT3018Y_BIT_HF;
> > +		err = i2c_smbus_write_byte_data(client, NCT3018Y_REG_CTRL, flags);
> > +		if (err < 0) {
> > +			dev_dbg(&client->dev, "Unable to write NCT3018Y_REG_CTRL\n");
> > +			return err;
> > +		}
> > +	} else if (flags & NCT3018Y_REG_PART_NCT3015Y) {
> > +		if (!(flags & data->part_number))
> > +			dev_warn(&client->dev, "%s: part_num=0x%x but NCT3018Y_REG_PART=0x%x\n",
> > +				 __func__, data->part_number, flags);
> 
> I don't think this is correct. Kernel's job is not to verify the DT...
> and why would it verify the device based on DT? You have here device
> detection so use it directly without this dance of comparing with
> compatible/match data.
> 

I fully agree here, either you trust your DT or the device ID but do not
use both.


-- 
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com