i2c: slave-eeprom: Add read only mode

[sfrench/cifs-2.6.git] / drivers / i2c / i2c-slave-eeprom.c

diff --git a/drivers/i2c/i2c-slave-eeprom.c b/drivers/i2c/i2c-slave-eeprom.c
index be65d3842878d4ffe62817580e1b646fdd8a97f0..db9763cb4dae326067e44733342c1829bc1c0626 100644 (file)
--- a/drivers/i2c/i2c-slave-eeprom.c
+++ b/drivers/i2c/i2c-slave-eeprom.c
@@ -11,6 +11,13 @@
  * pointer, yet implementation is deferred until the need actually arises.
  */
 
+/*
+ * FIXME: What to do if only 8 bits of a 16 bit address are sent?
+ * The ST-M24C64 sends only 0xff then. Needs verification with other
+ * EEPROMs, though. We currently use the 8 bit as a valid address.
+ */
+
+#include <linux/bitfield.h>
 #include <linux/i2c.h>
 #include <linux/init.h>
 #include <linux/module.h>
@@ -21,12 +28,20 @@
 
 struct eeprom_data {
        struct bin_attribute bin;
-       bool first_write;
        spinlock_t buffer_lock;
-       u8 buffer_idx;
+       u16 buffer_idx;
+       u16 address_mask;
+       u8 num_address_bytes;
+       u8 idx_write_cnt;
+       bool read_only;
        u8 buffer[];
 };
 
+#define I2C_SLAVE_BYTELEN GENMASK(15, 0)
+#define I2C_SLAVE_FLAG_ADDR16 BIT(16)
+#define I2C_SLAVE_FLAG_RO BIT(17)
+#define I2C_SLAVE_DEVICE_MAGIC(_len, _flags) ((_flags) | (_len))
+
 static int i2c_slave_eeprom_slave_cb(struct i2c_client *client,
                                     enum i2c_slave_event event, u8 *val)
 {
@@ -34,13 +49,17 @@ static int i2c_slave_eeprom_slave_cb(struct i2c_client *client,
 
        switch (event) {
        case I2C_SLAVE_WRITE_RECEIVED:
-               if (eeprom->first_write) {
-                       eeprom->buffer_idx = *val;
-                       eeprom->first_write = false;
+               if (eeprom->idx_write_cnt < eeprom->num_address_bytes) {
+                       if (eeprom->idx_write_cnt == 0)
+                               eeprom->buffer_idx = 0;
+                       eeprom->buffer_idx = *val | (eeprom->buffer_idx << 8);
+                       eeprom->idx_write_cnt++;
                } else {
-                       spin_lock(&eeprom->buffer_lock);
-                       eeprom->buffer[eeprom->buffer_idx++] = *val;
-                       spin_unlock(&eeprom->buffer_lock);
+                       if (!eeprom->read_only) {
+                               spin_lock(&eeprom->buffer_lock);
+                               eeprom->buffer[eeprom->buffer_idx++ & eeprom->address_mask] = *val;
+                               spin_unlock(&eeprom->buffer_lock);
+                       }
                }
                break;
 
@@ -50,7 +69,7 @@ static int i2c_slave_eeprom_slave_cb(struct i2c_client *client,
                /* fallthrough */
        case I2C_SLAVE_READ_REQUESTED:
                spin_lock(&eeprom->buffer_lock);
-               *val = eeprom->buffer[eeprom->buffer_idx];
+               *val = eeprom->buffer[eeprom->buffer_idx & eeprom->address_mask];
                spin_unlock(&eeprom->buffer_lock);
                /*
                 * Do not increment buffer_idx here, because we don't know if
@@ -61,7 +80,7 @@ static int i2c_slave_eeprom_slave_cb(struct i2c_client *client,
 
        case I2C_SLAVE_STOP:
        case I2C_SLAVE_WRITE_REQUESTED:
-               eeprom->first_write = true;
+               eeprom->idx_write_cnt = 0;
                break;
 
        default:
@@ -105,13 +124,17 @@ static int i2c_slave_eeprom_probe(struct i2c_client *client, const struct i2c_de
 {
        struct eeprom_data *eeprom;
        int ret;
-       unsigned size = id->driver_data;
+       unsigned int size = FIELD_GET(I2C_SLAVE_BYTELEN, id->driver_data);
+       unsigned int flag_addr16 = FIELD_GET(I2C_SLAVE_FLAG_ADDR16, id->driver_data);
 
        eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL);
        if (!eeprom)
                return -ENOMEM;
 
-       eeprom->first_write = true;
+       eeprom->idx_write_cnt = 0;
+       eeprom->num_address_bytes = flag_addr16 ? 2 : 1;
+       eeprom->address_mask = size - 1;
+       eeprom->read_only = FIELD_GET(I2C_SLAVE_FLAG_RO, id->driver_data);
        spin_lock_init(&eeprom->buffer_lock);
        i2c_set_clientdata(client, eeprom);
 
@@ -146,7 +169,12 @@ static int i2c_slave_eeprom_remove(struct i2c_client *client)
 }
 
 static const struct i2c_device_id i2c_slave_eeprom_id[] = {
-       { "slave-24c02", 2048 / 8 },
+       { "slave-24c02", I2C_SLAVE_DEVICE_MAGIC(2048 / 8,  0) },
+       { "slave-24c02ro", I2C_SLAVE_DEVICE_MAGIC(2048 / 8,  I2C_SLAVE_FLAG_RO) },
+       { "slave-24c32", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16) },
+       { "slave-24c32ro", I2C_SLAVE_DEVICE_MAGIC(32768 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
+       { "slave-24c64", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16) },
+       { "slave-24c64ro", I2C_SLAVE_DEVICE_MAGIC(65536 / 8, I2C_SLAVE_FLAG_ADDR16 | I2C_SLAVE_FLAG_RO) },
        { }
 };
 MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id);