On Fri, 07 Apr 2017, Linus Walleij wrote:

On Sun, Apr 2, 2017 at 10:42 PM, Paul Cercueil [off-list ref] wrote:

quoted

This driver handles pin configuration and pin muxing for the
JZ4740 and JZ4780 SoCs from Ingenic.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>

(...)

quoted

+       select MFD_CORE

(...)

quoted

+#include <linux/mfd/core.h>

That's unorthodox. Still quite pretty!
I would nee Lee Jones to say something about this, as it is
essentially hijacking MFD into the pinctrl subsystem.

quoted

+static struct mfd_cell ingenic_pinctrl_mfd_cells[] = {
+       {
+               .id = 0,
+               .name = "GPIOA",
+               .of_compatible = "ingenic,gpio-bank-a",
+       },
+       {
+               .id = 1,
+               .name = "GPIOB",
+               .of_compatible = "ingenic,gpio-bank-b",
+       },
+       {
+               .id = 2,
+               .name = "GPIOC",
+               .of_compatible = "ingenic,gpio-bank-c",
+       },
+       {
+               .id = 3,
+               .name = "GPIOD",
+               .of_compatible = "ingenic,gpio-bank-d",
+       },
+       {
+               .id = 4,
+               .name = "GPIOE",
+               .of_compatible = "ingenic,gpio-bank-e",
+       },
+       {
+               .id = 5,
+               .name = "GPIOF",
+               .of_compatible = "ingenic,gpio-bank-f",
+       },
+};

(...)

quoted

+       err = devm_mfd_add_devices(dev, 0, ingenic_pinctrl_mfd_cells,
+                       ARRAY_SIZE(ingenic_pinctrl_mfd_cells), NULL, 0, NULL);
+       if (err) {
+               dev_err(dev, "Failed to add MFD devices\n");
+               return err;
+       }

I guess the alternative would be to reimplement the MFD structure.

Did you check the approach to use "simple-mfd" and just let the subnodes
spawn as devices that way? I guess you did and this adds something
necessary.

I'd like to hear what the OP has to say about why this is necessary.
However, as a first glimpse, I'm dead against exporting MFD
functionality to outside of the subsystem.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
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