linux-kernel - Re: [PATCH 11/13] soc: qcom: Simplify with of_machine_get_match

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Message-ID: <a06ed143-c497-4141-8b4d-98fcb322e130@linaro.org>
Date: Fri, 7 Nov 2025 08:08:28 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Krzysztof Kozlowski <krzk@...nel.org>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Rob Herring <robh@...nel.org>, Saravana Kannan <saravanak@...gle.com>,
 "Rafael J. Wysocki" <rafael@...nel.org>,
 Viresh Kumar <viresh.kumar@...aro.org>,
 Matthias Brugger <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Yangtao Li <tiny.windzz@...il.com>, Chen-Yu Tsai <wens@...nel.org>,
 Jernej Skrabec <jernej.skrabec@...il.com>,
 Samuel Holland <samuel@...lland.org>,
 Lorenzo Pieralisi <lpieralisi@...nel.org>,
 Daniel Lezcano <daniel.lezcano@...aro.org>,
 Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>, Thomas Gleixner
 <tglx@...utronix.de>, Nicolas Ferre <nicolas.ferre@...rochip.com>,
 Alexandre Belloni <alexandre.belloni@...tlin.com>,
 Claudiu Beznea <claudiu.beznea@...on.dev>,
 Maximilian Luz <luzmaximilian@...il.com>, Hans de Goede <hansg@...nel.org>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 Daniel Lezcano <daniel.lezcano@...nel.org>,
 Thierry Reding <thierry.reding@...il.com>,
 Jonathan Hunter <jonathanh@...dia.com>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org,
 linux-sunxi@...ts.linux.dev, linux-arm-msm@...r.kernel.org,
 platform-driver-x86@...r.kernel.org, linux-tegra@...r.kernel.org
Subject: Re: [PATCH 11/13] soc: qcom: Simplify with
 of_machine_get_match_data()

On 07/11/2025 08:02, Krzysztof Kozlowski wrote:
> On 07/11/2025 04:19, Dmitry Baryshkov wrote:
>> On Thu, Nov 06, 2025 at 08:07:18PM +0100, Krzysztof Kozlowski wrote:
>>> Replace open-coded getting root OF node, matching against it and getting
>>> the match data with new of_machine_get_match_data() helper.
>>>
>>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>>>
>>> ---
>>>
>>> Depends on the first OF patch.
>>> ---
>>>  drivers/soc/qcom/qcom_pd_mapper.c | 17 ++---------------
>>>  1 file changed, 2 insertions(+), 15 deletions(-)
>>>
>>> diff --git a/drivers/soc/qcom/qcom_pd_mapper.c b/drivers/soc/qcom/qcom_pd_mapper.c
>>> index 1bcbe69688d2..07198d44b559 100644
>>> --- a/drivers/soc/qcom/qcom_pd_mapper.c
>>> +++ b/drivers/soc/qcom/qcom_pd_mapper.c
>>> @@ -613,25 +613,12 @@ static void qcom_pdm_stop(struct qcom_pdm_data *data)
>>>  static struct qcom_pdm_data *qcom_pdm_start(void)
>>>  {
>>>  	const struct qcom_pdm_domain_data * const *domains;
>>> -	const struct of_device_id *match;
>>>  	struct qcom_pdm_data *data;
>>> -	struct device_node *root;
>>>  	int ret, i;
>>>  
>>> -	root = of_find_node_by_path("/");
>>> -	if (!root)
>>> -		return ERR_PTR(-ENODEV);
>>> -
>>> -	match = of_match_node(qcom_pdm_domains, root);
>>> -	of_node_put(root);
>>> -	if (!match) {
>>> -		pr_notice("PDM: no support for the platform, userspace daemon might be required.\n");
>>> -		return ERR_PTR(-ENODEV);
>>> -	}
>>> -
>>> -	domains = match->data;
>>> +	domains = of_machine_get_match_data(qcom_pdm_domains);
>>>  	if (!domains) {
>>> -		pr_debug("PDM: no domains\n");
>>> +		pr_notice("PDM: no support for the platform or no domains, userspace daemon might be required.\n");
>>>  		return ERR_PTR(-ENODEV);
>>>  	}
>>
>> Here you are mixing two cases:
>> - There is not match in the table (in which case the driver should print
>>   a notice)
>>
>> - There is a match in the table, but the data is NULL (the platform
>>   doesn't have PDM domains). In this case there should be no notice.
> 
> 
> Why? Existing code printed notice in both cases. Why refactoring which
> tries to keep code functionally equivalent should change it?

Ah, you mean there was a debug before. Well, then I am a bit confused
because table has entries without data (so expected condition) but old
code returned ERRNO in such case - so unexpected condition.

Wail failing the probe on expected condition?

Unless it is not really expected and notice in second case is valid as well.

Best regards,
Krzysztof