i2c: slave-eeprom: add eeprom simulator driver

The first user of the i2c-slave interface is an eeprom simulator. It is
a shared memory which can be accessed by the remote master via I2C and
locally via sysfs.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

3 files changed, 181 insertions, 0 deletions

diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index b51a402752c4..8c9e619f3026 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -110,6 +110,16 @@ config I2C_STUB
 
           If you don't know what to do here, definitely say N.
 
+config I2C_SLAVE
+        bool "I2C slave support"
+
+if I2C_SLAVE
+
+config I2C_SLAVE_EEPROM
+        tristate "I2C eeprom slave driver"
+
+endif
+
 config I2C_DEBUG_CORE
         bool "I2C Core debugging messages"
         help
diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index 1722f50f2473..45095b3d16a9 100644
--- a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -9,6 +9,7 @@ obj-$(CONFIG_I2C_CHARDEV)	+= i2c-dev.o
 obj-$(CONFIG_I2C_MUX)           += i2c-mux.o
 obj-y                           += algos/ busses/ muxes/
 obj-$(CONFIG_I2C_STUB)          += i2c-stub.o
+obj-$(CONFIG_I2C_SLAVE_EEPROM)  += i2c-slave-eeprom.o
 
 ccflags-$(CONFIG_I2C_DEBUG_CORE) := -DDEBUG
 CFLAGS_i2c-core.o := -Wno-deprecated-declarations
diff --git a/drivers/i2c/i2c-slave-eeprom.c b/drivers/i2c/i2c-slave-eeprom.c
new file mode 100644
index 000000000000..6631400b5f02
--- /dev/null
+++ b/drivers/i2c/i2c-slave-eeprom.c
@@ -0,0 +1,170 @@
+/*
+ * I2C slave mode EEPROM simulator
+ *
+ * Copyright (C) 2014 by Wolfram Sang, Sang Engineering <wsa@sang-engineering.com>
+ * Copyright (C) 2014 by Renesas Electronics Corporation
+ *
+ * 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; version 2 of the License.
+ *
+ * Because most IP blocks can only detect one I2C slave address anyhow, this
+ * driver does not support simulating EEPROM types which take more than one
+ * address. It is prepared to simulate bigger EEPROMs with an internal 16 bit
+ * pointer, yet implementation is deferred until the need actually arises.
+ */
+
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/sysfs.h>
+
+struct eeprom_data {
+        struct bin_attribute bin;
+        bool first_write;
+        spinlock_t buffer_lock;
+        u8 buffer_idx;
+        u8 buffer[];
+};
+
+static int i2c_slave_eeprom_slave_cb(struct i2c_client *client,
+                                     enum i2c_slave_event event, u8 *val)
+{
+        struct eeprom_data *eeprom = i2c_get_clientdata(client);
+
+        switch (event) {
+        case I2C_SLAVE_REQ_WRITE_END:
+                if (eeprom->first_write) {
+                        eeprom->buffer_idx = *val;
+                        eeprom->first_write = false;
+                } else {
+                        spin_lock(&eeprom->buffer_lock);
+                        eeprom->buffer[eeprom->buffer_idx++] = *val;
+                        spin_unlock(&eeprom->buffer_lock);
+                }
+                break;
+
+        case I2C_SLAVE_REQ_READ_START:
+                spin_lock(&eeprom->buffer_lock);
+                *val = eeprom->buffer[eeprom->buffer_idx];
+                spin_unlock(&eeprom->buffer_lock);
+                break;
+
+        case I2C_SLAVE_REQ_READ_END:
+                eeprom->buffer_idx++;
+                break;
+
+        case I2C_SLAVE_STOP:
+                eeprom->first_write = true;
+                break;
+
+        default:
+                break;
+        }
+
+        return 0;
+}
+
+static ssize_t i2c_slave_eeprom_bin_read(struct file *filp, struct kobject *kobj,
+                struct bin_attribute *attr, char *buf, loff_t off, size_t count)
+{
+        struct eeprom_data *eeprom;
+        unsigned long flags;
+
+        if (off + count >= attr->size)
+                return -EFBIG;
+
+        eeprom = dev_get_drvdata(container_of(kobj, struct device, kobj));
+
+        spin_lock_irqsave(&eeprom->buffer_lock, flags);
+        memcpy(buf, &eeprom->buffer[off], count);
+        spin_unlock_irqrestore(&eeprom->buffer_lock, flags);
+
+        return count;
+}
+
+static ssize_t i2c_slave_eeprom_bin_write(struct file *filp, struct kobject *kobj,
+                struct bin_attribute *attr, char *buf, loff_t off, size_t count)
+{
+        struct eeprom_data *eeprom;
+        unsigned long flags;
+
+        if (off + count >= attr->size)
+                return -EFBIG;
+
+        eeprom = dev_get_drvdata(container_of(kobj, struct device, kobj));
+
+        spin_lock_irqsave(&eeprom->buffer_lock, flags);
+        memcpy(&eeprom->buffer[off], buf, count);
+        spin_unlock_irqrestore(&eeprom->buffer_lock, flags);
+
+        return count;
+}
+
+static int i2c_slave_eeprom_probe(struct i2c_client *client, const struct i2c_device_id *id)
+{
+        struct eeprom_data *eeprom;
+        int ret;
+        unsigned size = id->driver_data;
+
+        eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL);
+        if (!eeprom)
+                return -ENOMEM;
+
+        eeprom->first_write = true;
+        spin_lock_init(&eeprom->buffer_lock);
+        i2c_set_clientdata(client, eeprom);
+
+        sysfs_bin_attr_init(&eeprom->bin);
+        eeprom->bin.attr.name = "slave-eeprom";
+        eeprom->bin.attr.mode = S_IRUSR | S_IWUSR;
+        eeprom->bin.read = i2c_slave_eeprom_bin_read;
+        eeprom->bin.write = i2c_slave_eeprom_bin_write;
+        eeprom->bin.size = size;
+
+        ret = sysfs_create_bin_file(&client->dev.kobj, &eeprom->bin);
+        if (ret)
+                return ret;
+
+        ret = i2c_slave_register(client, i2c_slave_eeprom_slave_cb);
+        if (ret) {
+                sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
+                return ret;
+        }
+
+        return 0;
+};
+
+static int i2c_slave_eeprom_remove(struct i2c_client *client)
+{
+        struct eeprom_data *eeprom = i2c_get_clientdata(client);
+
+        i2c_slave_unregister(client);
+        sysfs_remove_bin_file(&client->dev.kobj, &eeprom->bin);
+
+        return 0;
+}
+
+static const struct i2c_device_id i2c_slave_eeprom_id[] = {
+        { "slave-24c02", 2048 / 8 },
+        { }
+};
+MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id);
+
+static struct i2c_driver i2c_slave_eeprom_driver = {
+        .driver = {
+                .name = "i2c-slave-eeprom",
+                .owner = THIS_MODULE,
+        },
+        .probe = i2c_slave_eeprom_probe,
+        .remove = i2c_slave_eeprom_remove,
+        .id_table = i2c_slave_eeprom_id,
+};
+module_i2c_driver(i2c_slave_eeprom_driver);
+
+MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
+MODULE_DESCRIPTION("I2C slave mode EEPROM simulator");
+MODULE_LICENSE("GPL v2");