linux-kernel - Re: [RESEND PATCH] regulator: userspace-consumer: Retrieve supplies from DT

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Date:   Sat, 23 Sep 2023 05:02:57 -0700
From:   Zev Weiss <zev@...ilderbeest.net>
To:     Naresh Solanki <naresh.solanki@...ements.com>
Cc:     broonie@...nel.org, Liam Girdwood <lgirdwood@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH] regulator: userspace-consumer: Retrieve supplies
 from DT

Hi Naresh,

This looks basically alright to me, though a few suggested tweaks 
below...

On Fri, Sep 22, 2023 at 02:03:29AM PDT, Naresh Solanki wrote:
>From: Naresh Solanki <Naresh.Solanki@...ements.com>
>
>Instead of hardcoding a single supply, retrieve supplies from DT.
>
>Signed-off-by: Naresh Solanki <Naresh.Solanki@...ements.com>
>---
> drivers/regulator/userspace-consumer.c | 43 ++++++++++++++++++++++++--
> 1 file changed, 40 insertions(+), 3 deletions(-)
>
>diff --git a/drivers/regulator/userspace-consumer.c b/drivers/regulator/userspace-consumer.c
>index 97f075ed68c9..a3d3e1e6ca74 100644
>--- a/drivers/regulator/userspace-consumer.c
>+++ b/drivers/regulator/userspace-consumer.c
>@@ -115,11 +115,32 @@ static const struct attribute_group attr_group = {
> 	.is_visible =  attr_visible,
> };
>
>+#define SUPPLY_SUFFIX "-supply"
>+#define SUPPLY_SUFFIX_LEN 7

I think 'strlen(SUPPLY_SUFFIX)' would be preferable to a numeric literal 
here; it's less fragile and the compiler can evaluate it at compile-time 
anyway (not that it's likely to be performance-critical in this context 
I'd expect).

>+
>+static int get_num_supplies(struct platform_device *pdev)
>+{
>+	struct  property *prop;
>+	int num_supplies = 0;
>+
>+	for_each_property_of_node(pdev->dev.of_node, prop) {
>+		const char *prop_name = prop->name;
>+		int len = strlen(prop_name);
>+
>+		if (len > SUPPLY_SUFFIX_LEN &&
>+		    strcmp(prop_name + len - SUPPLY_SUFFIX_LEN, SUPPLY_SUFFIX) == 0) {
>+			num_supplies++;
>+		}

Preferred coding style is to omit braces around single-line 'if' blocks.

>+	}
>+	return num_supplies;
>+}
>+
> 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;
>+	struct  property *prop;

Looks like there's an extra space after 'struct' here.

> 	int ret;
>
> 	pdata = dev_get_platdata(&pdev->dev);
>@@ -131,11 +152,27 @@ 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 = get_num_supplies(pdev);
>+
>+		pdata->supplies = devm_kzalloc(&pdev->dev, pdata->num_supplies *
>+					       sizeof(*pdata->supplies), GFP_KERNEL);

Splitting the multiplication across two lines like that isn't great 
readability-wise IMO; it might be better to just assign it to a variable 
and use that instead to make things fit nicely.

> 		if (!pdata->supplies)
> 			return -ENOMEM;
>-		pdata->supplies[0].supply = "vout";
>+
>+		for_each_property_of_node(pdev->dev.of_node, prop) {
>+			const char *prop_name = prop->name;
>+			int len = strlen(prop_name);
>+
>+			if (len > SUPPLY_SUFFIX_LEN &&
>+			    strcmp(prop_name + len - SUPPLY_SUFFIX_LEN, SUPPLY_SUFFIX) == 0) {

Rather than duplicating this suffix-checking code, how about factoring 
out a helper function like prop_is_supply() or something to use both 
here and in get_num_supplies()?

Or actually to make it integrate here a little more nicely, you could 
have something like 'size_t prop_supply_name(char*)', returning zero if 
it doesn't end with "-supply", and the length of the name before the 
suffix if it does, so that get_num_supplies() could use it as a boolean 
and the code below could use the length to determine the allocation 
size.

>+				char *supply_name = devm_kzalloc(&pdev->dev,
>+								 len - SUPPLY_SUFFIX_LEN + 1,
>+								 GFP_KERNEL);
>+				strscpy(supply_name, prop_name, len - SUPPLY_SUFFIX_LEN);
>+				supply_name[len - SUPPLY_SUFFIX_LEN] = '\0';
>+				pdata->supplies[0].supply = supply_name;
>+			}
>+		}
> 	}
>
> 	if (pdata->num_supplies < 1) {
>
>base-commit: 451e85e29c9d6f20639d4cfcff4b9dea280178cc
>-- 
>2.41.0
>