linux-kernel - Re: [PATCH v3 1/3] input: pm8xxx-vib: refactor to easily support new SPMI vibrator

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Message-ID: <a27ad44c-bbc9-0a2e-44fe-ee9b787d0cd4@linaro.org>
Date:   Thu, 27 Jul 2023 11:22:45 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Fenglin Wu <quic_fenglinw@...cinc.com>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        krzysztof.kozlowski+dt@...aro.org, robh+dt@...nel.org,
        agross@...nel.org, andersson@...nel.org,
        dmitry.baryshkov@...aro.org,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-input@...r.kernel.org
Cc:     quic_collinsd@...cinc.com, quic_subbaram@...cinc.com,
        quic_kamalw@...cinc.com, jestar@....qualcomm.com
Subject: Re: [PATCH v3 1/3] input: pm8xxx-vib: refactor to easily support new
 SPMI vibrator

On 27/07/2023 09:43, Fenglin Wu wrote:
> 
> 
> On 7/27/2023 3:07 PM, Krzysztof Kozlowski wrote:
>> On 25/07/2023 08:16, Fenglin Wu wrote:
>>>>>    
>>>>> -static const struct pm8xxx_regs pm8058_regs = {
>>>>> -	.drv_addr = 0x4A,
>>>>> -	.drv_mask = 0xf8,
>>>>> -	.drv_shift = 3,
>>>>> -	.drv_en_manual_mask = 0xfc,
>>>>> +static struct reg_field ssbi_vib_regs[VIB_MAX_REG] = {
>>>>
>>>> Change from const to non-const is wrong. How do you support multiple
>>>> devices? No, this is way too fragile now.
>>>>
>>>
>>> The register definition is no longer used as the match data, hw_type is
>>> used.
>>>
>>> The last suggestion was getting the register base address from the DT
>>> and it has to be added into the offset of SPMI vibrator registers
>>> (either in the previous hard-coded format or the later the reg_filed
>>> data structure), so it's not appropriated to make it constant.
>>>
>>> I don't understand this question: "How do you support multiple devices?"
>>> For SSBI vibrator, since all the registers are fixed, and I would assume
>>> that there is no chance to support multiple vibrator devices on the same
>>> SSBI bus. If they are not on the same bus, the regmap device will be
>>> different while the registers definition is the same, and we are still
>>> able to support multiple devices, right?
>>
>> No, you have static memory. One device probes and changes static memory
>> to reg+=base1. Second device probes and changes the same to reg+=base2.
> 
> Thanks, got it.  I can update it with following 2 options:
> 
> 1) keep the register definition in 'reg_filed' data structure and make 
> it constant, copy it to a dynamically allocated memory before adding the 
> 'reg_base' to the '.reg' variable.
> 
> 2) Define the register offsets as constant data and add the 'reg_base' 
> to the 'reg' while using 'regmap_read()'/'regmap_write()' functions.
> 
> which one is the preferred way?

Depends on the code. I am not sure if 2 would work with regmap_fields.
OTOH, I wonder if the device could just create its own regmap instead of
using parents? Then there would be no need of this offset dance.

Anyway, adding offset only for some variants seems also not needed. You
should add offset to each variant, because each device has this offset.

Best regards,
Krzysztof