i2c: Add i2c_board_info and i2c_new_device()

This provides partial support for new-style I2C driver binding.  It builds
on "struct i2c_board_info" declarations that identify I2C devices on a given
board.  This is needed on systems with I2C devices that can't be fully probed
and/or autoconfigured, such as many embedded Linux configurations where the
way a given I2C device is wired may affect how it must be used.

There are two models for declaring such devices:

 * LATE -- using a public function i2c_new_device().  This lets modules
   declare I2C devices found *AFTER* a given I2C adapter becomes available.
   
   For example, a PCI card could create adapters giving access to utility
   chips on that card, and this would be used to associate those chips with
   those adapters.

 * EARLY -- from arch_initcall() level code, using a non-exported function
   i2c_register_board_info().  This copies the declarations *BEFORE* such
   an i2c_adapter becomes available, arranging that i2c_new_device() will
   be called later when i2c-core registers the relevant i2c_adapter.

   For example, arch/.../.../board-*.c files would declare the I2C devices
   along with their platform data, and I2C devices would behave much like
   PNPACPI devices.  (That is, both enumerate from board-specific tables.)

To match the exported i2c_new_device(), the previously-private function
i2c_unregister_device() is now exported.

Pending later patches using these new APIs, this is effectively a NOP.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

drivers/i2c/i2c-boardinfo.c

@@ -0,0 +1,90 @@
+/*
+ * i2c-boardinfo.h - collect pre-declarations of I2C devices
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <linux/kernel.h>
+#include <linux/i2c.h>
+
+#include "i2c-core.h"
+
+
+/* These symbols are exported ONLY FOR the i2c core.
+ * No other users will be supported.
+ */
+DEFINE_MUTEX(__i2c_board_lock);
+EXPORT_SYMBOL_GPL(__i2c_board_lock);
+
+LIST_HEAD(__i2c_board_list);
+EXPORT_SYMBOL_GPL(__i2c_board_list);
+
+int __i2c_first_dynamic_bus_num;
+EXPORT_SYMBOL_GPL(__i2c_first_dynamic_bus_num);
+
+
+/**
+ * i2c_register_board_info - statically declare I2C devices
+ * @busnum: identifies the bus to which these devices belong
+ * @info: vector of i2c device descriptors
+ * @len: how many descriptors in the vector; may be zero to reserve
+ *	the specified bus number.
+ *
+ * Systems using the Linux I2C driver stack can declare tables of board info
+ * while they initialize.  This should be done in board-specific init code
+ * near arch_initcall() time, or equivalent, before any I2C adapter driver is
+ * registered.  For example, mainboard init code could define several devices,
+ * as could the init code for each daughtercard in a board stack.
+ *
+ * The I2C devices will be created later, after the adapter for the relevant
+ * bus has been registered.  After that moment, standard driver model tools
+ * are used to bind "new style" I2C drivers to the devices.  The bus number
+ * for any device declared using this routine is not available for dynamic
+ * allocation.
+ *
+ * The board info passed can safely be __initdata, but be careful of embedded
+ * pointers (for platform_data, functions, etc) since that won't be copied.
+ */
+int __init
+i2c_register_board_info(int busnum,
+	struct i2c_board_info const *info, unsigned len)
+{
+	int status;
+
+	mutex_lock(&__i2c_board_lock);
+
+	/* dynamic bus numbers will be assigned after the last static one */
+	if (busnum >= __i2c_first_dynamic_bus_num)
+		__i2c_first_dynamic_bus_num = busnum + 1;
+
+	for (status = 0; len; len--, info++) {
+		struct i2c_devinfo	*devinfo;
+
+		devinfo = kzalloc(sizeof(*devinfo), GFP_KERNEL);
+		if (!devinfo) {
+			pr_debug("i2c-core: can't register boardinfo!\n");
+			status = -ENOMEM;
+			break;
+		}
+
+		devinfo->busnum = busnum;
+		devinfo->board_info = *info;
+		list_add_tail(&devinfo->list, &__i2c_board_list);
+	}
+
+	mutex_unlock(&__i2c_board_lock);
+
+	return status;
+}