i2c: core: Add support for best effort block read emulation

[firefly-linux-kernel-4.4.55.git] / drivers / i2c / i2c-core.c

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index a6780289c61d207085db0b4e61590183816733de..98f6c75b1d18e4d685d381d6c1b43056b3c99452 100644 (file)
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -3007,6 +3007,63 @@ trace:
 }
 EXPORT_SYMBOL(i2c_smbus_xfer);
 
+/**
+ * i2c_smbus_read_i2c_block_data_or_emulated - read block or emulate
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ * @length: Size of data block; SMBus allows at most I2C_SMBUS_BLOCK_MAX bytes
+ * @values: Byte array into which data will be read; big enough to hold
+ *     the data returned by the slave.  SMBus allows at most
+ *     I2C_SMBUS_BLOCK_MAX bytes.
+ *
+ * This executes the SMBus "block read" protocol if supported by the adapter.
+ * If block read is not supported, it emulates it using either word or byte
+ * read protocols depending on availability.
+ *
+ * The addresses of the I2C slave device that are accessed with this function
+ * must be mapped to a linear region, so that a block read will have the same
+ * effect as a byte read. Before using this function you must double-check
+ * if the I2C slave does support exchanging a block transfer with a byte
+ * transfer.
+ */
+s32 i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client *client,
+                                             u8 command, u8 length, u8 *values)
+{
+       u8 i = 0;
+       int status;
+
+       if (length > I2C_SMBUS_BLOCK_MAX)
+               length = I2C_SMBUS_BLOCK_MAX;
+
+       if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK))
+               return i2c_smbus_read_i2c_block_data(client, command, length, values);
+
+       if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA))
+               return -EOPNOTSUPP;
+
+       if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_WORD_DATA)) {
+               while ((i + 2) <= length) {
+                       status = i2c_smbus_read_word_data(client, command + i);
+                       if (status < 0)
+                               return status;
+                       values[i] = status & 0xff;
+                       values[i + 1] = status >> 8;
+                       i += 2;
+               }
+       }
+
+       while (i < length) {
+               status = i2c_smbus_read_byte_data(client, command + i);
+               if (status < 0)
+                       return status;
+               values[i] = status;
+               i++;
+       }
+
+       return i;
+}
+EXPORT_SYMBOL(i2c_smbus_read_i2c_block_data_or_emulated);
+
 #if IS_ENABLED(CONFIG_I2C_SLAVE)
 int i2c_slave_register(struct i2c_client *client, i2c_slave_cb_t slave_cb)
 {