diff options
authorLinus Torvalds <>2011-11-23 09:50:05 -0800
committerLinus Torvalds <>2011-11-23 09:50:05 -0800
commit5907c5f8adbd0bb7ab69124520304e5b25c8eb5e (patch)
parent0a2c986557b964453f8deeaf56f6d88bf3e65e92 (diff)
parenteff245c82f115059648cdce95dd68bb940f2b006 (diff)
Merge branch 'i2c-for-linus' of git://
* 'i2c-for-linus' of git:// i2c: Make i2cdev_notifier_call static i2c: Delete ANY_I2C_BUS i2c: Fix device name for 10-bit slave address i2c-algo-bit: Generate correct i2c address sequence for 10-bit target
5 files changed, 25 insertions, 24 deletions
diff --git a/Documentation/i2c/ten-bit-addresses b/Documentation/i2c/ten-bit-addresses
index e9890709c508..cdfe13901b99 100644
--- a/Documentation/i2c/ten-bit-addresses
+++ b/Documentation/i2c/ten-bit-addresses
@@ -1,22 +1,24 @@
The I2C protocol knows about two kinds of device addresses: normal 7 bit
addresses, and an extended set of 10 bit addresses. The sets of addresses
do not intersect: the 7 bit address 0x10 is not the same as the 10 bit
-address 0x10 (though a single device could respond to both of them). You
-select a 10 bit address by adding an extra byte after the address
- S Addr7 Rd/Wr ....
- S 11110 Addr10 Rd/Wr
-S is the start bit, Rd/Wr the read/write bit, and if you count the number
-of bits, you will see the there are 8 after the S bit for 7 bit addresses,
-and 16 after the S bit for 10 bit addresses.
+address 0x10 (though a single device could respond to both of them).
-WARNING! The current 10 bit address support is EXPERIMENTAL. There are
-several places in the code that will cause SEVERE PROBLEMS with 10 bit
-addresses, even though there is some basic handling and hooks. Also,
-almost no supported adapter handles the 10 bit addresses correctly.
+I2C messages to and from 10-bit address devices have a different format.
+See the I2C specification for the details.
-As soon as a real 10 bit address device is spotted 'in the wild', we
-can and will add proper support. Right now, 10 bit address devices
-are defined by the I2C protocol, but we have never seen a single device
-which supports them.
+The current 10 bit address support is minimal. It should work, however
+you can expect some problems along the way:
+* Not all bus drivers support 10-bit addresses. Some don't because the
+ hardware doesn't support them (SMBus doesn't require 10-bit address
+ support for example), some don't because nobody bothered adding the
+ code (or it's there but not working properly.) Software implementation
+ (i2c-algo-bit) is known to work.
+* Some optional features do not support 10-bit addresses. This is the
+ case of automatic detection and instantiation of devices by their,
+ drivers, for example.
+* Many user-space packages (for example i2c-tools) lack support for
+ 10-bit addresses.
+Note that 10-bit address devices are still pretty rare, so the limitations
+listed above could stay for a long time, maybe even forever if nobody
+needs them to be fixed.
diff --git a/drivers/i2c/algos/i2c-algo-bit.c b/drivers/i2c/algos/i2c-algo-bit.c
index 85584a547c25..525c7345fa0b 100644
--- a/drivers/i2c/algos/i2c-algo-bit.c
+++ b/drivers/i2c/algos/i2c-algo-bit.c
@@ -488,7 +488,7 @@ static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
if (flags & I2C_M_TEN) {
/* a ten bit address */
- addr = 0xf0 | ((msg->addr >> 7) & 0x03);
+ addr = 0xf0 | ((msg->addr >> 7) & 0x06);
bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
/* try extended address code...*/
ret = try_address(i2c_adap, addr, retries);
@@ -498,7 +498,7 @@ static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
return -ENXIO;
/* the remaining 8 bit address */
- ret = i2c_outb(i2c_adap, msg->addr & 0x7f);
+ ret = i2c_outb(i2c_adap, msg->addr & 0xff);
if ((ret != 1) && !nak_ok) {
/* the chip did not ack / xmission error occurred */
dev_err(&i2c_adap->dev, "died at 2nd address code\n");
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 131079a3e292..1e5606185b4f 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -539,8 +539,10 @@ i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
client->dev.type = &i2c_client_type;
client->dev.of_node = info->of_node;
+ /* For 10-bit clients, add an arbitrary offset to avoid collisions */
dev_set_name(&client->dev, "%d-%04x", i2c_adapter_id(adap),
- client->addr);
+ client->addr | ((client->flags & I2C_CLIENT_TEN)
+ ? 0xa000 : 0));
status = device_register(&client->dev);
if (status)
goto out_err;
diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
index c90ce50b619f..57a45ce84b2d 100644
--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -579,7 +579,7 @@ static int i2cdev_detach_adapter(struct device *dev, void *dummy)
return 0;
-int i2cdev_notifier_call(struct notifier_block *nb, unsigned long action,
+static int i2cdev_notifier_call(struct notifier_block *nb, unsigned long action,
void *data)
struct device *dev = data;
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index a81bf6d23b3e..07d103a06d64 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -432,9 +432,6 @@ void i2c_unlock_adapter(struct i2c_adapter *);
/* Internal numbers to terminate lists */
#define I2C_CLIENT_END 0xfffeU
-/* The numbers to use to set I2C bus address */
-#define ANY_I2C_BUS 0xffff
/* Construct an I2C_CLIENT_END-terminated array of i2c addresses */
#define I2C_ADDRS(addr, addrs...) \
((const unsigned short []){ addr, ## addrs, I2C_CLIENT_END })