linux-kernel - Re: [PATCH 2/2] regulator: userspace-consumer: Multiple regulators

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Date:   Thu, 20 Apr 2023 17:57:51 +0530
From:   Naresh Solanki <naresh.solanki@...ements.com>
To:     Zev Weiss <zev@...ilderbeest.net>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] regulator: userspace-consumer: Multiple regulators

Hi Zev,

On 20-04-2023 04:27 pm, Zev Weiss wrote:
> On Thu, Apr 20, 2023 at 01:46:14AM PDT, Naresh Solanki wrote:
>> Hi Zev,
>>
>> On 20-04-2023 05:32 am, Zev Weiss wrote:
>>> On Tue, Apr 18, 2023 at 07:50:51AM PDT, Naresh Solanki wrote:
>>>> Use property regulator-supplies to determine all regulator
>>>> supplies.
>>>> This is useful in case of a connector having 2 or more supplies.
>>>> Example: PCIe connector on mainboard can be powered by 12V & 3.3V
>>>> suplies.
>>>>
>>>> Signed-off-by: Naresh Solanki <Naresh.Solanki@...ements.com>
>>>> ---
>>>> drivers/regulator/userspace-consumer.c | 19 +++++++++++++++----
>>>> 1 file changed, 15 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/regulator/userspace-consumer.c 
>>>> b/drivers/regulator/userspace-consumer.c
>>>> index 97f075ed68c9..0bb49547b926 100644
>>>> --- a/drivers/regulator/userspace-consumer.c
>>>> +++ b/drivers/regulator/userspace-consumer.c
>>>> @@ -120,7 +120,10 @@ static int 
>>>> regulator_userspace_consumer_probe(struct platform_device *pdev)
>>>>     struct regulator_userspace_consumer_data tmpdata;
>>>>     struct regulator_userspace_consumer_data *pdata;
>>>>     struct userspace_consumer_data *drvdata;
>>>> -    int ret;
>>>> +    struct device_node *np = pdev->dev.of_node;
>>>> +    struct property *prop;
>>>> +    const char *supply;
>>>> +    int ret, count = 0;
>>>>
>>>>     pdata = dev_get_platdata(&pdev->dev);
>>>>     if (!pdata) {
>>>> @@ -131,11 +134,19 @@ static int 
>>>> regulator_userspace_consumer_probe(struct platform_device *pdev)
>>>>         memset(pdata, 0, sizeof(*pdata));
>>>>
>>>>         pdata->no_autoswitch = true;
>>>> -        pdata->num_supplies = 1;
>>>> -        pdata->supplies = devm_kzalloc(&pdev->dev, 
>>>> sizeof(*pdata->supplies), GFP_KERNEL);
>>>> +        pdata->num_supplies = of_property_count_strings(np, 
>>>> "regulator-supplies");
>>>> +        if (pdata->num_supplies < 0) {
>>>> +            dev_err(&pdev->dev, "could not parse property 
>>>> regulator-supplies");
>>>> +            return -EINVAL;
>>>> +        }
>>>> +        pdata->supplies = devm_kzalloc(&pdev->dev,
>>>> +                           sizeof(*pdata->supplies) * 
>>>> pdata->num_supplies,
>>>> +                           GFP_KERNEL);
>>>
>>> AFAICT this doesn't appear to implement the "vout" default specified 
>>> in the dt-binding patch?
>> The "regulator-supplies" property will hold the default value of 
>> "vout" unless specified otherwise. As a result, the string enumeration 
>> retrieves the value of "vout" by default, and the "vout-supply" 
>> property is utilized for the regulator.
>>
> 
> With the disclaimer that I'm not a DT expert, that's not my 
> understanding of how DT works.  I don't think the 'default' value 
> specified in the binding forces the fdt to always include that value if 
> it's not present in the dts (since I'm pretty sure dtc doesn't even look 
> at the binding to know that a default exists when compiling the dts); 
> rather, it's information meant to be used by the software implementing 
> support for that device (e.g. a driver for it) about what value to 
> assume if the property isn't present in the fdt.
I apologize for the oversight on my part. Upon further testing, I have 
discovered that the default did not reflect in the debug prints. I will 
address this issue and include the proper fix in the next patchset. 
Thank you for bringing this to my attention
> 
>>>
>>> Also, since the core of the userspace-consumer driver itself already 
>>> supports multiple regulators, it might be nice for the subject line 
>>> to mention DT supplies or something a bit more specifically.
>> Sure. How about 'Support multiple supplies' ?
> 
> I meant that it should explicitly mention "DT" (or perhaps "OF").  The 
> driver's structure has supported multiple supplies since it was first 
> introduced in 2009, so "Support multiple supplies" sounds like this 
> commit is adding functionality that was already there.  What this patch 
> is doing is connecting that existing support to the OF support logic so 
> that it can be used in a device-tree context.
Sure. Will make it something like "Support multiple supplies in DT".
> 
>>>
>>>>         if (!pdata->supplies)
>>>>             return -ENOMEM;
>>>> -        pdata->supplies[0].supply = "vout";
>>>> +
>>>> +        of_property_for_each_string(np, "regulator-supplies", prop, 
>>>> supply)
>>>> +            pdata->supplies[count++].supply = supply;
>>>>     }
>>>>
>>>>     if (pdata->num_supplies < 1) {
>>>> -- 
>>>> 2.39.1
>>>>
>>>>
>> Regards,
>> Naresh
Regards,
Naresh