diff options
| -rw-r--r-- | drivers/misc/eeprom/at24.c | 125 |
1 files changed, 71 insertions, 54 deletions
diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c index 2efb572757cc..e7db1377e210 100644 --- a/drivers/misc/eeprom/at24.c +++ b/drivers/misc/eeprom/at24.c @@ -165,6 +165,19 @@ MODULE_DEVICE_TABLE(acpi, at24_acpi_ids); * This routine supports chips which consume multiple I2C addresses. It * computes the addressing information to be used for a given r/w request. * Assumes that sanity checks for offset happened at sysfs-layer. + * + * Slave address and byte offset derive from the offset. Always + * set the byte address; on a multi-master board, another master + * may have changed the chip's "current" address pointer. + * + * REVISIT some multi-address chips don't rollover page reads to + * the next slave address, so we may need to truncate the count. + * Those chips might need another quirk flag. + * + * If the real hardware used four adjacent 24c02 chips and that + * were misconfigured as one 24c08, that would be a similar effect: + * one "eeprom" file not four, but larger reads would fail when + * they crossed certain pages. */ static struct i2c_client *at24_translate_offset(struct at24_data *at24, unsigned int *offset) @@ -182,74 +195,77 @@ static struct i2c_client *at24_translate_offset(struct at24_data *at24, return at24->client[i]; } -static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf, - unsigned int offset, size_t count) +static ssize_t at24_eeprom_read_smbus(struct at24_data *at24, char *buf, + unsigned int offset, size_t count) { - struct i2c_msg msg[2]; - u8 msgbuf[2]; + unsigned long timeout, read_time; struct i2c_client *client; + int status; + + client = at24_translate_offset(at24, &offset); + + if (count > io_limit) + count = io_limit; + + /* Smaller eeproms can work given some SMBus extension calls */ + if (count > I2C_SMBUS_BLOCK_MAX) + count = I2C_SMBUS_BLOCK_MAX; + + loop_until_timeout(timeout, read_time) { + status = i2c_smbus_read_i2c_block_data_or_emulated(client, + offset, + count, buf); + + dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n", + count, offset, status, jiffies); + + if (status == count) + return count; + } + + return -ETIMEDOUT; +} + +static ssize_t at24_eeprom_read_i2c(struct at24_data *at24, char *buf, + unsigned int offset, size_t count) +{ unsigned long timeout, read_time; + struct i2c_client *client; + struct i2c_msg msg[2]; int status, i; + u8 msgbuf[2]; memset(msg, 0, sizeof(msg)); - - /* - * REVISIT some multi-address chips don't rollover page reads to - * the next slave address, so we may need to truncate the count. - * Those chips might need another quirk flag. - * - * If the real hardware used four adjacent 24c02 chips and that - * were misconfigured as one 24c08, that would be a similar effect: - * one "eeprom" file not four, but larger reads would fail when - * they crossed certain pages. - */ - - /* - * Slave address and byte offset derive from the offset. Always - * set the byte address; on a multi-master board, another master - * may have changed the chip's "current" address pointer. - */ client = at24_translate_offset(at24, &offset); if (count > io_limit) count = io_limit; - if (at24->use_smbus) { - /* Smaller eeproms can work given some SMBus extension calls */ - if (count > I2C_SMBUS_BLOCK_MAX) - count = I2C_SMBUS_BLOCK_MAX; - } else { - /* - * When we have a better choice than SMBus calls, use a - * combined I2C message. Write address; then read up to - * io_limit data bytes. Note that read page rollover helps us - * here (unlike writes). msgbuf is u8 and will cast to our - * needs. - */ - i = 0; - if (at24->chip.flags & AT24_FLAG_ADDR16) - msgbuf[i++] = offset >> 8; - msgbuf[i++] = offset; + /* + * When we have a better choice than SMBus calls, use a combined I2C + * message. Write address; then read up to io_limit data bytes. Note + * that read page rollover helps us here (unlike writes). msgbuf is + * u8 and will cast to our needs. + */ + i = 0; + if (at24->chip.flags & AT24_FLAG_ADDR16) + msgbuf[i++] = offset >> 8; + msgbuf[i++] = offset; - msg[0].addr = client->addr; - msg[0].buf = msgbuf; - msg[0].len = i; + msg[0].addr = client->addr; + msg[0].buf = msgbuf; + msg[0].len = i; - msg[1].addr = client->addr; - msg[1].flags = I2C_M_RD; - msg[1].buf = buf; - msg[1].len = count; - } + msg[1].addr = client->addr; + msg[1].flags = I2C_M_RD; + msg[1].buf = buf; + msg[1].len = count; loop_until_timeout(timeout, read_time) { - if (at24->use_smbus) { - status = i2c_smbus_read_i2c_block_data_or_emulated(client, offset, - count, buf); - } else { - status = i2c_transfer(client->adapter, msg, 2); - if (status == 2) - status = count; - } + status = i2c_transfer(client->adapter, msg, 2); + if (status == 2) + status = count; + dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n", count, offset, status, jiffies); @@ -520,7 +536,8 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id) at24->chip = chip; at24->num_addresses = num_addresses; - at24->read_func = at24_eeprom_read; + at24->read_func = at24->use_smbus ? at24_eeprom_read_smbus + : at24_eeprom_read_i2c; at24->write_func = at24_eeprom_write; writable = !(chip.flags & AT24_FLAG_READONLY); |