From 01eef96e37d77cd89156e5f51aab81a9d5c96539 Mon Sep 17 00:00:00 2001 From: Irina Tirdea Date: Wed, 12 Aug 2015 17:31:33 +0300 Subject: [PATCH] i2c: core: Add support for best effort block read emulation There are devices that need to handle block transactions regardless of the capabilities exported by the adapter. For performance reasons, they need to use i2c read blocks if available, otherwise emulate the block transaction with word or byte transactions. Add support for a helper function that would read a data block using the best transfer available: I2C_FUNC_SMBUS_READ_I2C_BLOCK, I2C_FUNC_SMBUS_READ_WORD_DATA or I2C_FUNC_SMBUS_READ_BYTE_DATA. Signed-off-by: Irina Tirdea Signed-off-by: Wolfram Sang --- drivers/i2c/i2c-core.c | 57 ++++++++++++++++++++++++++++++++++++++++++ include/linux/i2c.h | 3 +++ 2 files changed, 60 insertions(+) diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c index a6780289c61d..98f6c75b1d18 100644 --- 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) { diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 5aea07137218..768063baafbf 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -121,6 +121,9 @@ extern s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client, extern s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client, u8 command, u8 length, const u8 *values); +extern s32 +i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client *client, + u8 command, u8 length, u8 *values); #endif /* I2C */ /** -- 2.20.1