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

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Date:   Mon, 27 Jun 2022 10:37:31 +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

Hi Lee,


On 6/20/2022 4:37 PM, Satya Priya Kakitapalli (Temp) wrote:
>
> 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.
>

Could you please confirm on this?


>> What's preventing you from passing 'regmap'?
>
>
> I didn't get what you meant here, could you please elaborate a bit?
>
>