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

[Zev Weiss]

On Sat, Sep 23, 2023 at 05:02:59AM PDT, Zev Weiss wrote:
> 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@xxxxxxxxxxxxx>
> >
> > Instead of hardcoding a single supply, retrieve supplies from DT.
> >
> > Signed-off-by: Naresh Solanki <Naresh.Solanki@xxxxxxxxxxxxx>
> > ---
> > 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 

Or rather prop_supply_name_len(), to make the name a bit more accurate.

> 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';

Also, kstrndup() would be a cleaner replacement for these lines, though 
then the cleanup would get messy, and sadly a devm_kstrndup() doesn't 
currently exist -- maybe it'd be worth adding separately?  Or 
alternately you could just use devm_kstrdup() and then truncate it by 
inserting a '\0'.

> > +				pdata->supplies[0].supply = supply_name;
> > +			}
> > +		}
> > 	}
> >
> > 	if (pdata->num_supplies < 1) {
> >
> > base-commit: 451e85e29c9d6f20639d4cfcff4b9dea280178cc
> > --
> > 2.41.0