[PATCH 1/2] powerpc: gpio_mdio: Use devm_mdiobus_alloc_size()

[Christophe JAILLET]

Use mdiobus_alloc_size() instead of a hand written mdiobus_alloc() +
kzalloc().

This is less verbose and more robust. It also reduces memory fragmentation
and saves a few bytes of memory.

While at it, switch to devm_mdiobus_alloc_size() for extra simplification.

Signed-off-by: Christophe JAILLET <christophe.jail...@wanadoo.fr>
---
This patch is compile tested only.

Some memory is saved because pahole states, on a x86_64,  that:

struct mii_bus {
        ...
        /* size: 3640, cachelines: 57, members: 23 */
        /* sum members: 3633, holes: 2, sum holes: 7 */
        /* member types with holes: 3, total: 4, bit paddings: 1, total: 1 bit 
*/
        /* paddings: 1, sum paddings: 3 */
        /* forced alignments: 1, forced holes: 1, sum forced holes: 4 */
        /* last cacheline: 56 bytes */
}

Because of the way allocation works, 4096 bytes are allocated. When
mdiobus_alloc_size() is used, struct gpio_priv fits in this "wasted" space
and so is available "for free".
---
 arch/powerpc/platforms/pasemi/gpio_mdio.c | 26 +++++------------------
 1 file changed, 5 insertions(+), 21 deletions(-)

diff --git a/arch/powerpc/platforms/pasemi/gpio_mdio.c 
b/arch/powerpc/platforms/pasemi/gpio_mdio.c
index e4538d471256..2c54f5f063b7 100644
--- a/arch/powerpc/platforms/pasemi/gpio_mdio.c
+++ b/arch/powerpc/platforms/pasemi/gpio_mdio.c
@@ -213,15 +213,11 @@ static int gpio_mdio_probe(struct platform_device *ofdev)
        const unsigned int *prop;
        int err;
 
-       err = -ENOMEM;
-       priv = kzalloc(sizeof(struct gpio_priv), GFP_KERNEL);
-       if (!priv)
-               goto out;
-
-       new_bus = mdiobus_alloc();
-
+       new_bus = devm_mdiobus_alloc_size(dev, sizeof(*priv));
        if (!new_bus)
-               goto out_free_priv;
+               return -ENOMEM;
+
+       priv = new_bus->priv;
 
        new_bus->name = "pasemi gpio mdio bus";
        new_bus->read = &gpio_mdio_read;
@@ -230,7 +226,6 @@ static int gpio_mdio_probe(struct platform_device *ofdev)
 
        prop = of_get_property(np, "reg", NULL);
        snprintf(new_bus->id, MII_BUS_ID_SIZE, "%x", *prop);
-       new_bus->priv = priv;
 
        prop = of_get_property(np, "mdc-pin", NULL);
        priv->mdc_pin = *prop;
@@ -246,17 +241,10 @@ static int gpio_mdio_probe(struct platform_device *ofdev)
        if (err != 0) {
                pr_err("%s: Cannot register as MDIO bus, err %d\n",
                                new_bus->name, err);
-               goto out_free_irq;
+               return err;
        }
 
        return 0;
-
-out_free_irq:
-       kfree(new_bus);
-out_free_priv:
-       kfree(priv);
-out:
-       return err;
 }
 
 
@@ -267,10 +255,6 @@ static void gpio_mdio_remove(struct platform_device *dev)
        mdiobus_unregister(bus);
 
        dev_set_drvdata(&dev->dev, NULL);
-
-       kfree(bus->priv);
-       bus->priv = NULL;
-       mdiobus_free(bus);
 }
 
 static const struct of_device_id gpio_mdio_match[] =
-- 
2.48.1