I2C/SPI drivers allocate gpio_chip structure already, so we don't need
'struct gpio_chip gc' in the OF GPIO subsystem, instead we need to store
just a pointer, and then attach the already allocated gpio_chip to the
of_gpio_chip structure.
With this patch there are two ways to register OF GPIO controllers:

1. Allocating the of_gpio_chip structure and passing the
   &of_gc->gc pointer to the gpiochip_add. (Can use container_of
   to convert the gpio_chip to the of_gpio_chip.)

2. Allocating and registering the gpio_chip structure separately
   from the of_gpio_chip. (Since two allocations are separate,
   container_of won't work.)

As time goes by we'll kill the first option.

Signed-off-by: Anton Vorontsov <avoront...@ru.mvista.com>
---
 arch/powerpc/platforms/83xx/mcu_mpc8349emitx.c |    1 +
 drivers/of/gpio.c                              |   23 +++++++++++++++++++++--
 include/linux/of_gpio.h                        |    3 ++-
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/platforms/83xx/mcu_mpc8349emitx.c 
b/arch/powerpc/platforms/83xx/mcu_mpc8349emitx.c
index 82a9bcb..73c7e6b 100644
--- a/arch/powerpc/platforms/83xx/mcu_mpc8349emitx.c
+++ b/arch/powerpc/platforms/83xx/mcu_mpc8349emitx.c
@@ -93,6 +93,7 @@ static int mcu_gpiochip_add(struct mcu *mcu)
        gc->base = -1;
        gc->set = mcu_gpio_set;
        gc->direction_output = mcu_gpio_dir_out;
+       of_gc->chip = gc;
        of_gc->gpio_cells = 2;
        of_gc->xlate = of_gpio_simple_xlate;
 
diff --git a/drivers/of/gpio.c b/drivers/of/gpio.c
index 6eea601..12c4af0 100644
--- a/drivers/of/gpio.c
+++ b/drivers/of/gpio.c
@@ -70,7 +70,7 @@ int of_get_gpio_flags(struct device_node *np, int index,
        if (ret < 0)
                goto err1;
 
-       ret += of_gc->gc.base;
+       ret += of_gc->chip->base;
 err1:
        of_node_put(gc);
 err0:
@@ -140,7 +140,7 @@ int of_gpio_simple_xlate(struct of_gpio_chip *of_gc, struct 
device_node *np,
                return -EINVAL;
        }
 
-       if (*gpio > of_gc->gc.ngpio)
+       if (*gpio > of_gc->chip->ngpio)
                return -EINVAL;
 
        if (flags)
@@ -178,6 +178,25 @@ int of_mm_gpiochip_add(struct device_node *np,
        struct of_gpio_chip *of_gc = &mm_gc->of_gc;
        struct gpio_chip *gc = &of_gc->gc;
 
+       /*
+        * Currently there are two ways to register OF GPIO controllers:
+        *
+        * 1. Allocating the of_gpio_chip structure and passing the
+        *    &of_gc->gc pointer to the gpiochip_add. (Can use container_of
+        *    to convert the gpio_chip to the of_gpio_chip.)
+        *
+        * 2. Allocating and registering the gpio_chip structure separately
+        *    from the of_gpio_chip. (Since two allocations are separate,
+        *    container_of won't work.)
+        *
+        * As time goes by we'll kill the first option. For now just check
+        * if it's the new-style registration or the old-style.
+        */
+       if (!of_gc->chip)
+               of_gc->chip = gc;
+       else
+               gc = of_gc->chip;
+
        gc->label = kstrdup(np->full_name, GFP_KERNEL);
        if (!gc->label)
                goto err0;
diff --git a/include/linux/of_gpio.h b/include/linux/of_gpio.h
index fc2472c..c74cb37 100644
--- a/include/linux/of_gpio.h
+++ b/include/linux/of_gpio.h
@@ -36,7 +36,8 @@ enum of_gpio_flags {
  * Generic OF GPIO chip
  */
 struct of_gpio_chip {
-       struct gpio_chip gc;
+       struct gpio_chip gc; /* legacy, don't use for a new code */
+       struct gpio_chip *chip;
        int gpio_cells;
        int (*xlate)(struct of_gpio_chip *of_gc, struct device_node *np,
                     const void *gpio_spec, enum of_gpio_flags *flags);
-- 
1.6.5.7

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