mlxsw: minimal: Add I2C support for Mellanox ASICs

Add I2C access support for Mellanox ASICs:
- Virtual Protocol Interconnect switches SwitchX, SwitchX2,
  providing InfiniBand, Ethernet and Fibre Channel connectivity;
- Infiniband switches SwitchIB, SwitchIB2:
- Ethernet switch Spectrum.

Example of probing activation:
echo mlxsw_minimal 0x48 > /sys/bus/i2c/devices/i2c-2/new_device

Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/Kconfig

@@ -79,3 +79,14 @@ config MLXSW_SPECTRUM_DCB
 	---help---
 	  Say Y here if you want to use Data Center Bridging (DCB) in the
 	  driver.
+
+config MLXSW_MINIMAL
+	tristate "Mellanox Technologies minimal I2C support"
+	depends on MLXSW_CORE && MLXSW_I2C
+	default m
+	---help---
+	  This driver supports I2C access for Mellanox Technologies Switch
+	  ASICs.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called mlxsw_minimal.

drivers/net/ethernet/mellanox/mlxsw/Makefile

@@ -14,3 +14,5 @@ mlxsw_spectrum-objs		:= spectrum.o spectrum_buffers.o \
 				   spectrum_switchdev.o spectrum_router.o \
 				   spectrum_kvdl.o
 mlxsw_spectrum-$(CONFIG_MLXSW_SPECTRUM_DCB)	+= spectrum_dcb.o
+obj-$(CONFIG_MLXSW_MINIMAL)	+= mlxsw_minimal.o
+mlxsw_minimal-objs		:= minimal.o

drivers/net/ethernet/mellanox/mlxsw/minimal.c

@@ -0,0 +1,97 @@
+/*
+ * drivers/net/ethernet/mellanox/mlxsw/minimal.c
+ * Copyright (c) 2016 Mellanox Technologies. All rights reserved.
+ * Copyright (c) 2016 Vadim Pasternak <vadimp@mellanox.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the names of the copyright holders nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * Alternatively, this software may be distributed under the terms of the
+ * GNU General Public License ("GPL") version 2 as published by the Free
+ * Software Foundation.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <linux/i2c.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/types.h>
+
+#include "core.h"
+#include "i2c.h"
+
+static const char mlxsw_minimal_driver_name[] = "mlxsw_minimal";
+
+static const struct mlxsw_config_profile mlxsw_minimal_config_profile;
+
+static struct mlxsw_driver mlxsw_minimal_driver = {
+	.kind		= mlxsw_minimal_driver_name,
+	.priv_size	= 1,
+	.profile	= &mlxsw_minimal_config_profile,
+};
+
+static const struct i2c_device_id mlxsw_minimal_i2c_id[] = {
+	{ "mlxsw_minimal", 0},
+	{ },
+};
+
+static struct i2c_driver mlxsw_minimal_i2c_driver = {
+	.driver.name = "mlxsw_minimal",
+	.class = I2C_CLASS_HWMON,
+	.id_table = mlxsw_minimal_i2c_id,
+};
+
+static int __init mlxsw_minimal_module_init(void)
+{
+	int err;
+
+	err = mlxsw_core_driver_register(&mlxsw_minimal_driver);
+	if (err)
+		return err;
+
+	err = mlxsw_i2c_driver_register(&mlxsw_minimal_i2c_driver);
+	if (err)
+		goto err_i2c_driver_register;
+
+	return 0;
+
+err_i2c_driver_register:
+	mlxsw_core_driver_unregister(&mlxsw_minimal_driver);
+
+	return err;
+}
+
+static void __exit mlxsw_minimal_module_exit(void)
+{
+	mlxsw_i2c_driver_unregister(&mlxsw_minimal_i2c_driver);
+	mlxsw_core_driver_unregister(&mlxsw_minimal_driver);
+}
+
+module_init(mlxsw_minimal_module_init);
+module_exit(mlxsw_minimal_module_exit);
+
+MODULE_LICENSE("Dual BSD/GPL");
+MODULE_AUTHOR("Vadim Pasternak <vadimp@mellanox.com>");
+MODULE_DESCRIPTION("Mellanox minimal driver");
+MODULE_DEVICE_TABLE(i2c, mlxsw_minimal_i2c_id);