linux-kernel - Re: [PATCH 0/4] regulator: add and use a helper for setting supply names

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Date:   Fri, 30 Aug 2019 10:15:50 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Jonathan Hunter <jonathanh@...dia.com>,
        JC Kuo <jckuo@...dia.com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-ide@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH 0/4] regulator: add and use a helper for setting supply
 names

On Fri, Aug 30, 2019 at 09:17:36AM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> 
> There are ~80 users of regulator bulk APIs that set the supply names
> in a for loop before using the bulk helpers.
> 
> This series proposes to add a helper function for setting supply names
> and uses it in a couple tegra drivers. If accepted: a coccinelle script
> should be easy to develop that would address this in other drivers.
> 
> Bartosz Golaszewski (4):
>   regulator: provide regulator_bulk_set_supply_names()
>   ahci: tegra: use regulator_bulk_set_supply_names()
>   phy: tegra: use regulator_bulk_set_supply_names()
>   usb: host: xhci-tegra: use regulator_bulk_set_supply_names()
> 
>  drivers/ata/ahci_tegra.c           |  6 +++---
>  drivers/phy/tegra/xusb.c           |  6 +++---
>  drivers/regulator/helpers.c        | 21 +++++++++++++++++++++
>  drivers/usb/host/xhci-tegra.c      |  5 +++--
>  include/linux/regulator/consumer.h | 12 ++++++++++++
>  5 files changed, 42 insertions(+), 8 deletions(-)

The diffstat here suggests that this isn't really helpful. Even if you
subtract the regulator code that adds the new helper, you actually have
a zero diffstat (and a positive one in one case).

Instead, why don't we take this one step further and roll a bit more of
the boilerplate into the new helper, something along these lines:

	struct regulator_bulk_data *
	devm_regulator_bulk_get_from_names(struct device *dev,
					   const char * const *supply_names,
					   unsigned int num_supplies)
	{
		struct regulator_bulk_data *data;
		unsigned int i;
		int err;

		data = devm_kcalloc(dev, num_supplies, sizeof(*data));
		if (!data)
			return ERR_PTR(-ENOMEM);

		for (i = 0; i < num_supplies; i++)
			data[i].supply = supply_names[i];

		err = devm_regulator_bulk_get(dev, num_supplies, data);
		if (err < 0)
			return ERR_PTR(err);

		return data;
	}

That seems to be still a very common pattern and gets rid of a lot more
boilerplate, so your diffstat will actually start to be negative at some
point.

I suppose one could add a non-managed variant for this as well, but I'm
counting 6 uses of regulator_bulk_get() vs. ~140 uses of the managed
variant, so I'm not sure it's worth it.

Thierry

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