[v2,0/6] Add support for software nodes to gpiolib

This series attempts to add support for software nodes to gpiolib, using
software node references. This allows us to convert more drivers to the
generic device properties and drop support for custom platform data.

To describe a GPIO via software nodes we can create the following data
items:

/* Node representing the GPIO controller/GPIO bank */
static const struct software_node gpio_bank_b_node = {
        .name = "B",
};

/*
 * Properties that will be assigned to a software node assigned to
 * the device that used platform data.
 */
static const struct property_entry simone_key_enter_props[] = {
        PROPERTY_ENTRY_U32("linux,code", KEY_ENTER),
        PROPERTY_ENTRY_STRING("label", "enter"),
        PROPERTY_ENTRY_REF("gpios", &gpio_bank_b_node, 123, GPIO_ACTIVE_LOW),
        { }
};

The code in gpiolib handling software nodes uses the name in the
software node representing GPIO controller to locate the actual instance
of GPIO controller.

To: Linus Walleij <linus.walleij@linaro.org>
To: Bartosz Golaszewski <brgl@bgdev.pl>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: linux-gpio@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-acpi@vger.kernel.org

---
Changes in v2:
- reworked the series to be independent of other in-flight patches.
  That meant keeping devm_gpiod_get_from_of_node() for now.
- removed handling of secondary nodes, it deserves a separate patch
  series
- fixed refcounting when handling swnodes (Andy)
- added include/linux/gpio/property.h with PROPERTY_ENTRY_GPIO (Andy)
- addressed most of the rest of Andy's comments
- collected reviewed-by and acked-by
- Link to v1: https://lore.kernel.org/r/20221031-gpiolib-swnode-v1-0-a0ab48d229c7@gmail.com

---
Dmitry Torokhov (6):
      gpiolib: of: change of_find_gpio() to accept device node
      gpiolib: acpi: change acpi_find_gpio() to accept firmware node
      gpiolib: acpi: teach acpi_find_gpio() to handle data-only nodes
      gpiolib: acpi: avoid leaking ACPI details into upper gpiolib layers
      gpiolib: consolidate GPIO lookups
      gpiolib: add support for software nodes

 drivers/gpio/Makefile         |   1 +
 drivers/gpio/gpiolib-acpi.c   | 132 ++++++++++++++-----------
 drivers/gpio/gpiolib-acpi.h   |  54 +----------
 drivers/gpio/gpiolib-of.c     |   7 +-
 drivers/gpio/gpiolib-of.h     |   4 +-
 drivers/gpio/gpiolib-swnode.c | 128 ++++++++++++++++++++++++
 drivers/gpio/gpiolib-swnode.h |  14 +++
 drivers/gpio/gpiolib.c        | 219 +++++++++++++++++-------------------------
 include/linux/gpio/property.h |  11 +++
 9 files changed, 329 insertions(+), 241 deletions(-)
---
base-commit: b6fc3fddade7a194bd141a49f2689e50f796ef46
change-id: 20221031-gpiolib-swnode-948203f49b23

On Wed, Nov 09, 2022 at 11:00:29AM -0800, Dmitry Torokhov wrote:
> On Wed, Nov 09, 2022 at 01:25:06PM +0200, Andy Shevchenko wrote:
> > On Tue, Nov 08, 2022 at 04:26:50PM -0800, Dmitry Torokhov wrote:

...

> > > +static struct gpio_desc *gpiod_find_by_fwnode(struct fwnode_handle *fwnode,
> > > +					      struct device *consumer,
> > > +					      const char *con_id,
> > > +					      unsigned int idx,
> > > +					      enum gpiod_flags *flags,
> > > +					      unsigned long *lookupflags)
> > >  {
> > > -	unsigned long lflags = GPIO_LOOKUP_FLAGS_DEFAULT;
> > 
> > > -	struct gpio_desc *desc = ERR_PTR(-ENODEV);
> > 
> > Not sure why this is needed. Now I see that else branch has been changed,
> > but looking closer to it, we can drop it completely, while leaving this
> > line untouched, correct?
> 
> Yes. I believe removing an initializer and doing a series of if/else
> if/else was discussed and [soft] agreed-on in the previous review cycle,
> but I can change it back.
> 
> I think we still need to have it return -ENOENT and not -ENODEV/-EINVAL
> so that we can fall back to GPIO lookup tables when dealing with an
> unsupported node type.

Right, okay, let's go with whatever variant you find better.

...

> > > +	if (!IS_ERR_OR_NULL(fwnode))
> > 
> > I think this is superfluous check.
> > 
> > Now in the form of this series, you have only a single dev_dbg() that tries to
> > dereference it. Do we really need to have it there, since every branch has its
> > own dev_dbg() anyway?
> 
> As I mentioned, I like to keep this check to show the reader that we
> should only descend into gpiod_find_by_fwnode() if we have a valid
> fwnode. It is less about code generation and more about the intent.

Yes, but if fwnode is not found, we have a next check for that. I really don't
think we lose anything by dropping the check and gaining the code generation as
a side effect.

On Wed, Nov 09, 2022 at 11:32:31AM -0800, Dmitry Torokhov wrote:
> On Wed, Nov 09, 2022 at 01:29:41PM +0200, Andy Shevchenko wrote:
> > On Tue, Nov 08, 2022 at 04:26:45PM -0800, Dmitry Torokhov wrote:

...

> > Thank for an update!
> > 
> > I have almost nothing serious except two nit-picks I think we can address:
> > - dropping const qualifier for no (?) reason
> > - having a superfluous check and extra dev_dbg()
> > 
> > If you are are going to address them, feel free to add my Rb tag to
> > the patches 5 & 6.
> 
> Thank you for the reviews. I addressed most of your comments, but
> because I still left the check you were concerned about in I'd like an
> explicit reviewed-by on the v3 if you OK giving it.

I gave for patch 6 and for patch 5 I still think we can get rid of the check.