linux-kernel - Re: [PATCH V15 6/9] mfd: pm8008: Use i2c_new_dummy

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Message-ID: <a11732d6-a9b1-7ead-e89a-564a57a7192b@quicinc.com>
Date:   Mon, 20 Jun 2022 16:37:31 +0530
From:   "Satya Priya Kakitapalli (Temp)" <quic_c_skakit@...cinc.com>
To:     Lee Jones <lee.jones@...aro.org>
CC:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <swboyd@...omium.org>,
        <quic_collinsd@...cinc.com>, <quic_subbaram@...cinc.com>,
        <quic_jprakash@...cinc.com>
Subject: Re: [PATCH V15 6/9] mfd: pm8008: Use i2c_new_dummy_device() API


On 6/20/2022 1:50 PM, Lee Jones wrote:
> On Mon, 20 Jun 2022, Satya Priya Kakitapalli (Temp) wrote:
>
>> On 6/17/2022 2:27 AM, Lee Jones wrote:
>>> On Tue, 14 Jun 2022, Satya Priya wrote:
>>>
>>>> Use i2c_new_dummy_device() to register pm8008-regulator
>>>> client present at a different address space, instead of
>>>> defining a separate DT node. This avoids calling the probe
>>>> twice for the same chip, once for each client pm8008-infra
>>>> and pm8008-regulator.
>>>>
>>>> As a part of this define pm8008_regmap_init() to do regmap
>>>> init for both the clients and define pm8008_get_regmap() to
>>>> pass the regmap to the regulator driver.
>>>>
>>>> Signed-off-by: Satya Priya <quic_c_skakit@...cinc.com>
>>>> Reviewed-by: Stephen Boyd <swboyd@...omium.org>
>>>> ---
>>>> Changes in V15:
>>>>    - None.
>>>>
>>>> Changes in V14:
>>>>    - None.
>>>>
>>>> Changes in V13:
>>>>    - None.
>>>>
>>>>    drivers/mfd/qcom-pm8008.c       | 34 ++++++++++++++++++++++++++++++++--
>>>>    include/linux/mfd/qcom_pm8008.h |  9 +++++++++
>>>>    2 files changed, 41 insertions(+), 2 deletions(-)
>>>>    create mode 100644 include/linux/mfd/qcom_pm8008.h
>>>>
>>>> diff --git a/drivers/mfd/qcom-pm8008.c b/drivers/mfd/qcom-pm8008.c
>>>> index 569ffd50..55e2a8e 100644
>>>> --- a/drivers/mfd/qcom-pm8008.c
>>>> +++ b/drivers/mfd/qcom-pm8008.c
>>>> @@ -9,6 +9,7 @@
>>>>    #include <linux/interrupt.h>
>>>>    #include <linux/irq.h>
>>>>    #include <linux/irqdomain.h>
>>>> +#include <linux/mfd/qcom_pm8008.h>
>>>>    #include <linux/module.h>
>>>>    #include <linux/of_device.h>
>>>>    #include <linux/of_platform.h>
>>>> @@ -57,6 +58,7 @@ enum {
>>>>    struct pm8008_data {
>>>>    	struct device *dev;
>>>> +	struct regmap *regulators_regmap;
>>>>    	int irq;
>>>>    	struct regmap_irq_chip_data *irq_data;
>>>>    };
>>>> @@ -150,6 +152,12 @@ static struct regmap_config qcom_mfd_regmap_cfg = {
>>>>    	.max_register	= 0xFFFF,
>>>>    };
>>>> +struct regmap *pm8008_get_regmap(const struct pm8008_data *chip)
>>>> +{
>>>> +	return chip->regulators_regmap;
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(pm8008_get_regmap);
>>> Seems like abstraction for the sake of abstraction.
>>>
>>> Why not do the dereference inside the regulator driver?
>> To derefer this in the regulator driver, we need to have the pm8008_data
>> struct definition in the qcom_pm8008 header file.
>>
>> I think it doesn't look great to have only that structure in header and all
>> other structs and enum in the mfd driver.
> Then why pass 'pm8008_data' at all?


There is one more option, instead of passing the pm8008_data, we could 
pass the pdev->dev.parent and get the pm8008 chip data directly in the 
pm8008_get_regmap() like below


struct regmap *pm8008_get_regmap(const struct device *dev)
  {
      const struct pm8008_data *chip = dev_get_drvdata(dev);

      return chip->regulators_regmap;
}
EXPORT_SYMBOL_GPL(pm8008_get_regmap);


By doing this we can avoid having declaration of pm8008_data also in the 
header. Please let me know if this looks good.

> What's preventing you from passing 'regmap'?


I didn't get what you meant here, could you please elaborate a bit?