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

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Date:	Thu, 14 Jan 2016 10:08:56 +0900
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Laxman Dewangan <ldewangan@...dia.com>,
	Mark Brown <broonie@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Need APIs to add regmap in dev

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.

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

BR,
Krzysztof