linux-kernel - Re: Need APIs to add regmap in dev

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Message-ID: <56978AB6.3050001@nvidia.com>
Date:	Thu, 14 Jan 2016 17:17:02 +0530
From:	Laxman Dewangan <ldewangan@...dia.com>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Mark Brown <broonie@...nel.org>
CC:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Need APIs to add regmap in dev


On Thursday 14 January 2016 06:38 AM, Krzysztof Kozlowski wrote:
> On 14.01.2016 03:57, Laxman Dewangan wrote:
>> Hi Mark,
>> when working on unification of Max77620, MAX77686 RTC driver, I came to
>> need of APIs from regmap to add the device  as devres.
>>
>> int dev_add_regmap(dev, regmap);
>>
>> This will add the regmap in the dev resource of device. This will help
>> to get the regmap handle from device using dev_get_regmap(). This APIs
>> will be different from the regmap_attach_dev() where map->dev is moved
>> to new device.
>>
>> The requirement came from multiple i2c slave address device like MAX77620.
>> MAX77620 has 2 i2c address 0x3C and 0x68. 0x68 is for RTC IP block.
>> we register device with 0x3C and create dummy i2c client for 0x68 inside
>> driver.
>> We create two regmap, one from 0x3C i2c client as rmap_0x3c and other
>> from 0x68 i2c dummy client rmap_0x68.
>>
>> Now in RTC driver(mfd device), we have the parent device as dev_0x3c.
>> When we try to get the regmap handle, we only get one regmap per device
>> as we register regmap with different devices.
>>
>> If I had above API then I can add the rmap_0x68 in the dev_0x3c as
>> dev_res. By this I can have two regmap list on dev_0x3c and get rmap
>> handle by dev_get_regmap(dev_0x3c, "pmic-slave") and
>> dev_get_regmap(dev_0x3c, "rtc-slave");
>>
>>
>> I like to know your comment on this approach to add the regmap on
>> different device resource.
>
> As I pointed on previous discussions (e.g.
> https://lkml.org/lkml/2016/1/11/1158 ) the child should be responsible
> for its I2C dummy device and regmap. You ignored that idea previously -
> dunno why.

One of discussion, Mark suggested to use dev_get_regmap() and explored 
to get both regmap handle via this call. That's why did not routed to 
create one regmap in mfd and other regmap in the rtc driver.

>
> Just don't create the RTC regmap in parent MFD. Let the child manage its
> resources. That is the real decoupling.

This is also very possible to handle everything on RTC driver.
Will try this route now.