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-rw-r--r--drivers/misc/eeprom/at24.c59
1 files changed, 48 insertions, 11 deletions
diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index db7d0f21b65d..0c11e411d8ec 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -54,7 +54,7 @@
struct at24_data {
struct at24_platform_data chip;
struct memory_accessor macc;
- bool use_smbus;
+ int use_smbus;
/*
* Lock protects against activities from other Linux tasks,
@@ -184,11 +184,19 @@ static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
if (count > io_limit)
count = io_limit;
- if (at24->use_smbus) {
+ switch (at24->use_smbus) {
+ case I2C_SMBUS_I2C_BLOCK_DATA:
/* Smaller eeproms can work given some SMBus extension calls */
if (count > I2C_SMBUS_BLOCK_MAX)
count = I2C_SMBUS_BLOCK_MAX;
- } else {
+ break;
+ case I2C_SMBUS_WORD_DATA:
+ count = 2;
+ break;
+ case I2C_SMBUS_BYTE_DATA:
+ count = 1;
+ break;
+ default:
/*
* When we have a better choice than SMBus calls, use a
* combined I2C message. Write address; then read up to
@@ -219,10 +227,27 @@ static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
timeout = jiffies + msecs_to_jiffies(write_timeout);
do {
read_time = jiffies;
- if (at24->use_smbus) {
+ switch (at24->use_smbus) {
+ case I2C_SMBUS_I2C_BLOCK_DATA:
status = i2c_smbus_read_i2c_block_data(client, offset,
count, buf);
- } else {
+ break;
+ case I2C_SMBUS_WORD_DATA:
+ status = i2c_smbus_read_word_data(client, offset);
+ if (status >= 0) {
+ buf[0] = status & 0xff;
+ buf[1] = status >> 8;
+ status = count;
+ }
+ break;
+ case I2C_SMBUS_BYTE_DATA:
+ status = i2c_smbus_read_byte_data(client, offset);
+ if (status >= 0) {
+ buf[0] = status;
+ status = count;
+ }
+ break;
+ default:
status = i2c_transfer(client->adapter, msg, 2);
if (status == 2)
status = count;
@@ -434,7 +459,7 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
{
struct at24_platform_data chip;
bool writable;
- bool use_smbus = false;
+ int use_smbus = 0;
struct at24_data *at24;
int err;
unsigned i, num_addresses;
@@ -475,12 +500,19 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
err = -EPFNOSUPPORT;
goto err_out;
}
- if (!i2c_check_functionality(client->adapter,
+ 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,
+ I2C_FUNC_SMBUS_READ_WORD_DATA)) {
+ use_smbus = I2C_SMBUS_WORD_DATA;
+ } else if (i2c_check_functionality(client->adapter,
+ I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
+ use_smbus = I2C_SMBUS_BYTE_DATA;
+ } else {
err = -EPFNOSUPPORT;
goto err_out;
}
- use_smbus = true;
}
if (chip.flags & AT24_FLAG_TAKE8ADDR)
@@ -566,11 +598,16 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
dev_info(&client->dev, "%zu byte %s EEPROM %s\n",
at24->bin.size, client->name,
writable ? "(writable)" : "(read-only)");
+ if (use_smbus == I2C_SMBUS_WORD_DATA ||
+ use_smbus == I2C_SMBUS_BYTE_DATA) {
+ dev_notice(&client->dev, "Falling back to %s reads, "
+ "performance will suffer\n", use_smbus ==
+ I2C_SMBUS_WORD_DATA ? "word" : "byte");
+ }
dev_dbg(&client->dev,
- "page_size %d, num_addresses %d, write_max %d%s\n",
+ "page_size %d, num_addresses %d, write_max %d, use_smbus %d\n",
chip.page_size, num_addresses,
- at24->write_max,
- use_smbus ? ", use_smbus" : "");
+ at24->write_max, use_smbus);
/* export data to kernel code */
if (chip.setup)