MIPS: ath79: add common GPIO buttons device

Almost all boards have one or more push buttons connected to GPIO lines.
This patch adds common code to register a platform_device for them.

The patch also adds support for the buttons on the PB44 board.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Signed-off-by: Imre Kaloz <kaloz@openwrt.org>
Cc: linux-mips@linux-mips.org
Cc: Luis R. Rodriguez <lrodriguez@atheros.com>
Cc: Cliff Holden <Cliff.Holden@Atheros.com>
Cc: Kathy Giori <Kathy.Giori@Atheros.com>
Patchwork: https://patchwork.linux-mips.org/patch/1954/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/ath79/dev-gpio-buttons.c

@@ -0,0 +1,58 @@
+/*
+ *  Atheros AR71XX/AR724X/AR913X GPIO button support
+ *
+ *  Copyright (C) 2008-2010 Gabor Juhos <juhosg@openwrt.org>
+ *  Copyright (C) 2008 Imre Kaloz <kaloz@openwrt.org>
+ *
+ *  This program is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 2 as published
+ *  by the Free Software Foundation.
+ */
+
+#include "linux/init.h"
+#include "linux/slab.h"
+#include <linux/platform_device.h>
+
+#include "dev-gpio-buttons.h"
+
+void __init ath79_register_gpio_keys_polled(int id,
+					    unsigned poll_interval,
+					    unsigned nbuttons,
+					    struct gpio_keys_button *buttons)
+{
+	struct platform_device *pdev;
+	struct gpio_keys_platform_data pdata;
+	struct gpio_keys_button *p;
+	int err;
+
+	p = kmalloc(nbuttons * sizeof(*p), GFP_KERNEL);
+	if (!p)
+		return;
+
+	memcpy(p, buttons, nbuttons * sizeof(*p));
+
+	pdev = platform_device_alloc("gpio-keys-polled", id);
+	if (!pdev)
+		goto err_free_buttons;
+
+	memset(&pdata, 0, sizeof(pdata));
+	pdata.poll_interval = poll_interval;
+	pdata.nbuttons = nbuttons;
+	pdata.buttons = p;
+
+	err = platform_device_add_data(pdev, &pdata, sizeof(pdata));
+	if (err)
+		goto err_put_pdev;
+
+	err = platform_device_add(pdev);
+	if (err)
+		goto err_put_pdev;
+
+	return;
+
+err_put_pdev:
+	platform_device_put(pdev);
+
+err_free_buttons:
+	kfree(p);
+}