Large EEPROMS (24c32 and larger) require a two-byte data address instead of just a single byte. Implement support for such EEPROMs with SMBus commands.
Support has limitations (reads are not multi-master safe) and is slow, but it works. Practical use is for a system with 24c32 connected to Intel 82801I (ICH9). Signed-off-by: Guenter Roeck <[email protected]> --- drivers/misc/eeprom/at24.c | 52 +++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 47 insertions(+), 5 deletions(-) diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c index 2d3db81..057d35c 100644 --- a/drivers/misc/eeprom/at24.c +++ b/drivers/misc/eeprom/at24.c @@ -198,6 +198,8 @@ static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf, case I2C_SMBUS_BYTE_DATA: count = 1; break; + case I2C_SMBUS_BYTE: + break; default: /* * When we have a better choice than SMBus calls, use a @@ -249,6 +251,27 @@ static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf, status = count; } break; + case I2C_SMBUS_BYTE: + /* + * 16-bit data address. Write data address as separate + * write operation, then read data without setting + * the address again. This is not multi-master safe, + * but the best we can do. + */ + status = i2c_smbus_write_byte_data(client, + offset >> 8, + offset & 0xff); + if (status < 0) + break; + for (i = 0; i < count; i++) { + status = i2c_smbus_read_byte(client); + if (status < 0) + break; + buf[i] = status; + } + if (status >= 0) + status = count; + break; default: status = i2c_transfer(client->adapter, msg, 2); if (status == 2) @@ -372,6 +395,16 @@ static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf, status = i2c_smbus_write_i2c_block_data(client, offset, count, buf); break; + case I2C_SMBUS_WORD_DATA: + /* + * 16-bit data address. Transmit data address + * MSB as SMBus command, data address LSB as + * first data byte. + */ + status = i2c_smbus_write_word_data(client, + offset >> 8, + (offset & 0xff) | (buf[0] << 8)); + break; case I2C_SMBUS_BYTE_DATA: status = i2c_smbus_write_byte_data(client, offset, buf[0]); @@ -540,10 +573,13 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id) /* Use I2C operations unless we're stuck with SMBus extensions. */ if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) { - if (chip.flags & AT24_FLAG_ADDR16) - return -EPFNOSUPPORT; - - if (i2c_check_functionality(client->adapter, + if (chip.flags & AT24_FLAG_ADDR16) { + if (!i2c_check_functionality(client->adapter, + I2C_FUNC_SMBUS_WRITE_BYTE_DATA | + I2C_FUNC_SMBUS_READ_BYTE)) + return -EPFNOSUPPORT; + use_smbus = I2C_SMBUS_BYTE; + } else if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK)) { use_smbus = I2C_SMBUS_I2C_BLOCK_DATA; } else if (i2c_check_functionality(client->adapter, @@ -559,7 +595,13 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id) /* Use I2C operations unless we're stuck with SMBus extensions. */ if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) { - if (i2c_check_functionality(client->adapter, + if (chip.flags & AT24_FLAG_ADDR16) { + if (i2c_check_functionality(client->adapter, + I2C_FUNC_SMBUS_WRITE_WORD_DATA)) { + use_smbus_write = I2C_SMBUS_WORD_DATA; + chip.page_size = 1; + } + } else if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) { use_smbus_write = I2C_SMBUS_I2C_BLOCK_DATA; } else if (i2c_check_functionality(client->adapter, -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
