Richard Röjfors wrote:
I have an intel chipset which can do smbus, what is the difference
between smbus and i2c btw? I know that because previously I got a lot of
warnings (hundreds) indicating that i2c transfers were not supported.
SMBus is a wire protocol, which may be implemented on top of an i2c
bus. I2C provides the physical bus to get bytes on the wire, SMBus
describes what the bytes mean. For example, an SMBus byte write is
defined as
Start Bit - 7 bit I2C address - Write Bit (0) - (wait for ack bit from
client) - Data byte - (wait for ack bit) - Stop Bit
The conexant cx25840 digitizer doesn't speak SMBus, so we have to use a
I2C-level (raw) transfer, which the cx23416 lets us do. The old cx25840
detect code didn't check to see if raw transfers were supported, so any
i2c client on 0x44 was assumed to be a cx25840. Of course, that is
wrong but has been fixed.
cx25840: Module init
cx25840: starting probe for adapter ivtv i2c driver #0 (0x10005)
I have been seeing a lot of this recently. Normally that would be
followed by a line where it says that it found a cx25840 at 0x44, and
then give the revision number. For some reason the i2c_probe isn't
working. I've seen this in several people's logs both with PVR-150s and
500s. I'm not sure what's causing it though. It can be one of a few
things:
-- The ivtv i2c adapter isn't reporting it supports
I2C_FUNC_SMBUS_QUICK. Is there a version of i2c-algo-bit that doesn't
doesn't report functionality I2C_FUNC_SMBUS_EMUL?
-- i2c_check_addr() returns that 0x44 is already in use. One could
probably check sysfs to see if this is the case
(/sys/devices/platform/i2c-X/ would have an directory entry for X-0044)
-- The i2c_smbus_xfer(QUICK) is faling. What? Why would that happen?
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