linux-kernel - Re: [PATCH v2 08/12] pinctrl: qcom: use generic pin function helpers

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Message-ID: <b9f6f827-78bf-4fee-8be2-74a9c94d9722@oss.qualcomm.com>
Date: Fri, 11 Jul 2025 14:19:26 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Linus Walleij <linus.walleij@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Alexey Klimov <alexey.klimov@...aro.org>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Sean Wang <sean.wang@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
        Paul Cercueil <paul@...pouillou.net>, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-mips@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v2 08/12] pinctrl: qcom: use generic pin function helpers

On 7/10/25 3:38 PM, Bartosz Golaszewski wrote:
> On Thu, Jul 10, 2025 at 2:25 PM Konrad Dybcio
> <konrad.dybcio@....qualcomm.com> wrote:
>>
>> On 7/9/25 4:39 PM, Bartosz Golaszewski wrote:
>>> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>>>
>>> Use the existing infrastructure for storing and looking up pin functions
>>> in pinctrl core. Remove hand-crafted callbacks.
>>>
>>> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>>> ---
>>
>> [...]
>>
>>>  int msm_pinctrl_probe(struct platform_device *pdev,
>>>                     const struct msm_pinctrl_soc_data *soc_data)
>>>  {
>>> +     const struct pinfunction *func;
>>>       struct msm_pinctrl *pctrl;
>>>       struct resource *res;
>>>       int ret;
>>> @@ -1606,6 +1581,14 @@ int msm_pinctrl_probe(struct platform_device *pdev,
>>>               return PTR_ERR(pctrl->pctrl);
>>>       }
>>>
>>> +     for (i = 0; i < soc_data->nfunctions; i++) {
>>> +             func = &soc_data->functions[i];
>>> +
>>> +             ret = pinmux_generic_add_pinfunction(pctrl->pctrl, func, NULL);
>>> +             if (ret < 0)
>>> +                     return ret;
>>> +     }
>>
>> It's good in principle, but we're now going to house two copies of
>> the function data in memory... Can we trust __initconst nowadays?
>>
> 
> Well, if I annotate the functions struct with __initconst, then it
> does indeed end up in the .init.rodata section if that's your
> question. Then the kernel seems to be freeing this in
> ./kernel/module/main.c so I sure hope we can trust it.
> 
> Do I understand correctly that you're implicitly asking to also
> annotate all affected _functions structures across all tlmm drivers?
> 
> Alternatively: we can provide another interface:
> pinmux_generic_add_const_pinfunction() which - instead of a deep-copy
> - would simply store addresses of existing pinfunction structures in
> the underlying radix tree.

This option seems like less of a churn

Konrad