[PATCH v2 4/4] ACPI / gpio: Allow holes in list of GPIOs for a device

[Mika Westerberg]

Make it possible to have an empty GPIOs in a GPIO list for device. For
example a SPI master may use both GPIOs and native pins as chip selects and
we need to be able to distinguish between the two.

This makes it mandatory to have exactly 3 arguments for GPIOs and then
converts gpiolib to use of __acpi_node_get_property_reference() instead. In
addition we make acpi_gpio_package_count() to handle holes as well (this
matches the DT version).

Signed-off-by: Mika Westerberg <mika.westerb...@linux.intel.com>
---
 Documentation/acpi/gpio-properties.txt | 15 +++++++++++++++
 drivers/gpio/gpiolib-acpi.c            | 32 +++++++++++++++++++++-----------
 2 files changed, 36 insertions(+), 11 deletions(-)

diff --git a/Documentation/acpi/gpio-properties.txt 
b/Documentation/acpi/gpio-properties.txt
index 46df91c3512b..2ccb70893122 100644
--- a/Documentation/acpi/gpio-properties.txt
+++ b/Documentation/acpi/gpio-properties.txt
@@ -51,6 +51,21 @@ it to 1 marks the GPIO as active low.
 In our Bluetooth example the "reset-gpios" refers to the second GpioIo()
 resource, second pin in that resource with the GPIO number of 31.
 
+It is possible to leave holes in the array of GPIOs. This is useful in
+cases like with SPI host controllers where some chip selects may be
+implemented as GPIOs and some as native signals. For example a SPI host
+controller can have chip selects 0 and 2 implemented as GPIOs and 1 as
+native:
+
+  Package () {
+      "cs-gpios",
+      Package () {
+          ^GPIO, 19, 0, 0, // chip select 0: GPIO
+          0,               // chip select 1: native signal
+          ^GPIO, 20, 0, 0, // chip select 2: GPIO
+      }
+  }
+
 Other supported properties
 --------------------------
 
diff --git a/drivers/gpio/gpiolib-acpi.c b/drivers/gpio/gpiolib-acpi.c
index 4e50f8f5d597..096a94ee96e7 100644
--- a/drivers/gpio/gpiolib-acpi.c
+++ b/drivers/gpio/gpiolib-acpi.c
@@ -467,7 +467,8 @@ static int acpi_gpio_property_lookup(struct fwnode_handle 
*fwnode,
        int ret;
 
        memset(&args, 0, sizeof(args));
-       ret = acpi_node_get_property_reference(fwnode, propname, index, &args);
+       ret = __acpi_node_get_property_reference(fwnode, propname, index, 3,
+                                                &args);
        if (ret) {
                struct acpi_device *adev = to_acpi_device_node(fwnode);
 
@@ -482,13 +483,13 @@ static int acpi_gpio_property_lookup(struct fwnode_handle 
*fwnode,
         * on returned args.
         */
        lookup->adev = args.adev;
-       if (args.nargs >= 2) {
-               lookup->index = args.args[0];
-               lookup->pin_index = args.args[1];
-               /* 3rd argument, if present is used to specify active_low. */
-               if (args.nargs >= 3)
-                       lookup->active_low = !!args.args[2];
-       }
+       if (args.nargs != 3)
+               return -EPROTO;
+
+       lookup->index = args.args[0];
+       lookup->pin_index = args.args[1];
+       lookup->active_low = !!args.args[2];
+
        return 0;
 }
 
@@ -979,18 +980,27 @@ void acpi_gpiochip_remove(struct gpio_chip *chip)
        kfree(acpi_gpio);
 }
 
-static unsigned int acpi_gpio_package_count(const union acpi_object *obj)
+static int acpi_gpio_package_count(const union acpi_object *obj)
 {
        const union acpi_object *element = obj->package.elements;
        const union acpi_object *end = element + obj->package.count;
        unsigned int count = 0;
 
        while (element < end) {
-               if (element->type == ACPI_TYPE_LOCAL_REFERENCE)
+               switch (element->type) {
+               case ACPI_TYPE_LOCAL_REFERENCE:
+                       element += 3;
+                       /* Fallthrough */
+               case ACPI_TYPE_INTEGER:
+                       element++;
                        count++;
+                       break;
 
-               element++;
+               default:
+                       return -EPROTO;
+               }
        }
+
        return count;
 }
 
-- 
2.9.3