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linux-sg2042/Documentation/i2c/ten-bit-addresses

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Documentation/i2c: Checkpatch cleanup Remove all trailing whitespace in Documentation/i2c. Signed-off-by: Andrea Gelmini <andrea.gelmini@gelma.net> Signed-off-by: Jean Delvare <khali@linux-fr.org>
2010-06-03 17:33:50 +08:00
The I2C protocol knows about two kinds of device addresses: normal 7 bit
Linux-2.6.12-rc2 Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
2005-04-17 06:20:36 +08:00
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
i2c: Fix device name for 10-bit slave address 10-bit addresses overlap with traditional 7-bit addresses, leading in device name collisions. Add an arbitrary offset to 10-bit addresses to prevent this collision. The offset was chosen so that the address is still easily recognizable. Signed-off-by: Jean Delvare <khali@linux-fr.org> Acked-by: Wolfram Sang <w.sang@pengutronix.de>
2011-11-23 18:33:07 +08:00
address 0x10 (though a single device could respond to both of them).
i2c: support 10 bit and slave addresses in sysfs 'new_device' We now have seperate address spaces for 10 bit and we-are-slave clients. Update the sysfs device instantiation method to support these types by accepting the address offsets that are assigned to the extra address spaces. Update the documentation, too. Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2015-07-27 20:03:38 +08:00
To avoid ambiguity, the user sees 10 bit addresses mapped to a different
address space, namely 0xa000-0xa3ff. The leading 0xa (= 10) represents the
10 bit mode. This is used for creating device names in sysfs. It is also
needed when instantiating 10 bit devices via the new_device file in sysfs.
Linux-2.6.12-rc2 Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
2005-04-17 06:20:36 +08:00
i2c: Fix device name for 10-bit slave address 10-bit addresses overlap with traditional 7-bit addresses, leading in device name collisions. Add an arbitrary offset to 10-bit addresses to prevent this collision. The offset was chosen so that the address is still easily recognizable. Signed-off-by: Jean Delvare <khali@linux-fr.org> Acked-by: Wolfram Sang <w.sang@pengutronix.de>
2011-11-23 18:33:07 +08:00
I2C messages to and from 10-bit address devices have a different format.
See the I2C specification for the details.
Linux-2.6.12-rc2 Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
2005-04-17 06:20:36 +08:00
i2c: Fix device name for 10-bit slave address 10-bit addresses overlap with traditional 7-bit addresses, leading in device name collisions. Add an arbitrary offset to 10-bit addresses to prevent this collision. The offset was chosen so that the address is still easily recognizable. Signed-off-by: Jean Delvare <khali@linux-fr.org> Acked-by: Wolfram Sang <w.sang@pengutronix.de>
2011-11-23 18:33:07 +08:00
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.