linux-kernel - Re: [PATCH V2 5/6] rtc: max77xxx: add RTC driver for Maxim MAX77xxx series RTC IP

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Message-id: <5695D268.3060705@samsung.com>
Date:	Wed, 13 Jan 2016 13:28:24 +0900
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Laxman Dewangan <ldewangan@...dia.com>, robh+dt@...nel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	linus.walleij@...aro.org, gnurou@...il.com, lee.jones@...aro.org,
	broonie@...nel.org, a.zummo@...ertech.it,
	alexandre.belloni@...e-electrons.com
Cc:	lgirdwood@...il.com, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
	rtc-linux@...glegroups.com, swarren@...dia.com, treding@...dia.com
Subject: Re: [PATCH V2 5/6] rtc: max77xxx: add RTC driver for Maxim MAX77xxx
 series RTC IP

On 13.01.2016 13:07, Laxman Dewangan wrote:
> 
> On Wednesday 13 January 2016 05:36 AM, Krzysztof Kozlowski wrote:
>> On 12.01.2016 18:17, Laxman Dewangan wrote:
>>> Maxim Semiconductor's PMIC MAX77620, MAX77686, MAX20024 have
>>> same RTC IP on these PMICs.
>>>
>>> Add generic MAX77xxxx series RTC driver which can be used as
>>> RTC driver for these PMIC and avoids duplication of RTC driver
>>> for each PMICs. Their MFD driver can be different here.
>>>
>>> Signed-off-by: Laxman Dewangan <ldewangan@...dia.com>
>>> ---
>>> Changes from V1:
>>> - Rename the file to rtc-max77xxx.c and make the generic implementation.
>>> - Direct regmap apis are used for the register access.
>>> - Decouped from max77620 driver.
>>> - Taken care of cleanup comments form V1 version.
>>>
>>>   drivers/rtc/Kconfig        |  10 +
>>>   drivers/rtc/Makefile       |   1 +
>>>   drivers/rtc/rtc-max77xxx.c | 500
>>> +++++++++++++++++++++++++++++++++++++++++++++
>>>   3 files changed, 511 insertions(+)
>>>   create mode 100644 drivers/rtc/rtc-max77xxx.c
>>>
>>> diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
>>> index 376322f..4972dd5 100644
>>> --- a/drivers/rtc/Kconfig
>>> +++ b/drivers/rtc/Kconfig
>>> @@ -315,6 +315,16 @@ config RTC_DRV_MAX8997
>>>         This driver can also be built as a module. If so, the module
>>>         will be called rtc-max8997.
>>>   +config RTC_DRV_MAX77XXX
>>> +    tristate "Maxim MAX77XXX series generic RTC driver"
>>> +    help
>>> +      If you say yes here you will get support for the generic RTC
>>> driver
>>> +      for Maxim Semiconductor MAX77XXX series of PMIC like MAX77620.
>>> +      This also supports the RTC driver for Maxim PMIC MaX20024 which
>>> +      is almost same as MAX77620.
>>> +      This driver can also be built as a module. If so, the module
>>> +      will be called rtc-max77xxx.
>>> +
>> That was not the consensus... You still added a new driver - but now
>> with different name.
>>
>> That is useless duplication
>>
>> Please work with existing code. Use existing maxim RTC drivers: either
>> max77686 or max77802.
>>
>> There is no need for new one.
> 
> If we modify the existing one then that work will be outside of this
> series to make it independent.

And that is the problem? The series evolve. The ultimate goal is to
support max77686, max77802, max77620 and max20024.

> 
> However, the file name does not suggest common in older file.

This is not a sensible argument. The name does not matter. But if really
needed we can rename it...

> Also this
> will require mfd and rtc driver changes to decouple it.

Yes, decouple everything! I like it! :) Make it robust, generic,
readable, fix bugs etc. :)

> 
> Here is my approach:
> - Let's have common driver in implementation and file name. This will be
> independent of the mfd driver on all sense.
> - Once it is merged, move the max77686 and max77802 to use this driver,
> this will need the modification on the mfd driver, related defconfig
> file and if specific stuff needed in the rtc then addition of that.

Nope, because *the second part won't happen*. Never. After merging you
will be happy and another duplicated stuff ends in the kernel.

Fix things before merging. Not after.

> 
> Per your approach:
> - Modify rtc max77686 and mfd driver max77686 to decouple and proper
> registration.
> - Add support of max77620 on the max77686 driver if any specific is
> required.

That is the way we usually extend the drivers for new devices.

> 
> That is also fine to me but still I am not comfortable with the config
> name and driver file name as this does not suggest the common.

The name does not matter. Really. We have a lot of drivers with a
specific device-like name and supporting different devices. To point
that your argument is invalid - your initial name of driver
"rtc-max77620.c" supported totally different "names": the max77620 and
max20024. It also wasn't suggesting something "common"...

With my approach we are not developing common think neither. We just
want to extend/re-use existing max77686 (or max77802) driver for new
devices. Just like everywhere else.

Best regards,
Krzysztof