Introduce at24_smbus_write_i2c_block_data() to allow very slow write
access to 16-bit EEPROM devices attached to SMBus controllers like
the Intel I801.
With an AT24C512 device:
248 B/s with 1-byte page (default)
3.9 KB/s with 128-byte* page (via platform data)
*limited to 16-bytes by I2C_SMBUS_BLOCK_MAX / 2.
Signed-off-by: Aaron Sierra <asierra@xxxxxxxxxxx>
---
v2 - Unchanged from v1
drivers/misc/eeprom/at24.c | 35 ++++++++++++++++++++++++++++++++---
1 file changed, 32 insertions(+), 3 deletions(-)
diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
index c6cb7f8..c3d3add 100644
--- a/drivers/misc/eeprom/at24.c
+++ b/drivers/misc/eeprom/at24.c
@@ -134,6 +134,34 @@ MODULE_DEVICE_TABLE(i2c, at24_ids);
/*-------------------------------------------------------------------------*/
/*
+ * Write block data to an AT24 device using SMBus cycles.
+ */
+static inline s32 at24_smbus_write_i2c_block_data(struct at24_data *at24,
+ const struct i2c_client *client, u16 off, u8 len, const u8 *vals)
+{
+ u8 *addr16;
+ s32 res;
+
+ if (!(at24->chip.flags & AT24_FLAG_ADDR16))
+ return i2c_smbus_write_i2c_block_data(client, off, len, vals);
+
+ addr16 = kzalloc(len + 1, GFP_KERNEL);
+ if (!addr16)
+ return -ENOMEM;
+
+ /* Insert extra address byte into data stream */
+ addr16[0] = off & 0xff;
+ memcpy(addr16 + 1, vals, len);
+
+ res = i2c_smbus_write_i2c_block_data(client,
+ (off >> 8) & 0xff, len + 1, addr16);
+
+ kfree(addr16);
+
+ return res;
+}
+
+/*
* 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.
@@ -344,8 +372,8 @@ static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
if (at24->use_smbus_write) {
switch (at24->use_smbus_write) {
case I2C_SMBUS_I2C_BLOCK_DATA:
- status = i2c_smbus_write_i2c_block_data(client,
- offset, count, buf);
+ status = at24_smbus_write_i2c_block_data(at24,
+ client, offset, count, buf);
break;
case I2C_SMBUS_BYTE_DATA:
status = i2c_smbus_write_byte_data(client,
@@ -584,7 +612,8 @@ static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
if (write_max > io_limit)
write_max = io_limit;
if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX)
- write_max = I2C_SMBUS_BLOCK_MAX;
+ write_max = I2C_SMBUS_BLOCK_MAX >>
+ !!(chip.flags & AT24_FLAG_ADDR16);
at24->write_max = write_max;
/* buffer (data + address at the beginning) */
--
1.9.1
--
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