linux-kernel - Re: [PATCH v4 2/2] gpio: add a reusable generic gpio

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Date:   Wed, 27 May 2020 19:31:53 -0500
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Michael Walle <michael@...le.cc>
Cc:     linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Mark Brown <broonie@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v4 2/2] gpio: add a reusable generic gpio_chip using
 regmap

Hi Michael,

>>> +struct gpio_regmap_config {
>>> +    struct device *parent;
>>> +    struct regmap *regmap;
>>> +
>>> +    const char *label;
>>> +    int ngpio;
>>
>> could we add a .names field for the gpio_chip, I found this useful for
>> PCM512x GPIO support, e.g.
> 
> Sure, I have the names in the device tree.
> 
> But I'd prefer that you'd do a patch on top of this (assuming it is
> applied soon), because you can actually test it and there might be
> missing more.

I am happy to report that this gpio-regmap worked like a charm for me, 
after I applied the minor diff below (complete code at 
https://github.com/plbossart/sound/tree/fix/regmap-gpios).

I worked around my previous comments by forcing the GPIO internal 
routing directly in regmap, and that allowed me to only play with the 
_set and _dir bases. I see the LEDs and clock selected as before, quite 
nice indeed.

The chip->label test is probably wrong, since the gpio_chip structure is 
zeroed out if(!chip->label) is always true so the label is always set to 
the device name. I don't know what the intent was so just removed that 
test - maybe the correct test should be if (!config->label) ?

I added the names support as well, and btw I don't understand how one 
would get them through device tree?

I still have a series of odd warnings I didn't have before:

[  101.400263] WARNING: CPU: 3 PID: 1129 at drivers/gpio/gpiolib.c:4084 
gpiod_set_value+0x3f/0x50

This seems to come from
	/* Should be using gpiod_set_value_cansleep() */
	WARN_ON(desc->gdev->chip->can_sleep);

so maybe we need an option here as well? Or use a different function?

Anyways, that gpio-regmap does simplify my code a great deal so thanks 
for this work, much appreciated.
-Pierre

diff --git a/drivers/gpio/gpio-regmap.c b/drivers/gpio/gpio-regmap.c
index 3cb0e8493835..678d644a0a4b 100644
--- a/drivers/gpio/gpio-regmap.c
+++ b/drivers/gpio/gpio-regmap.c
@@ -251,10 +251,8 @@ struct gpio_regmap *gpio_regmap_register(const 
struct gpio_regmap_config *config
         chip->ngpio = config->ngpio;
         chip->can_sleep = true;

-       if (!chip->label)
-               chip->label = dev_name(config->parent);
-       else
-               chip->label = config->label;
+       chip->label = config->label;
+       chip->names = config->names;

         chip->get = gpio_regmap_get;
         if (gpio->reg_set_base && gpio->reg_clr_base)
diff --git a/include/linux/gpio-regmap.h b/include/linux/gpio-regmap.h
index bbdb2d79ef8f..c1f3e36ebf33 100644
--- a/include/linux/gpio-regmap.h
+++ b/include/linux/gpio-regmap.h
@@ -16,6 +16,7 @@ struct gpio_regmap;
   *                     given, the name of the device is used
   * @label:             (Optional) Descriptive name for GPIO controller.
   *                     If not given, the name of the device is used.
+ * @names:             (Optional) Array of names for gpios
   * @ngpio:             Number of GPIOs
   * @reg_dat_base:      (Optional) (in) register base address
   * @reg_set_base:      (Optional) set register base address
@@ -43,6 +44,7 @@ struct gpio_regmap_config {
         struct regmap *regmap;

         const char *label;
+       const char *const *names;
         int ngpio;

         unsigned int reg_dat_base;