I'm running linux 2.6.34.7 with the i2c-parport-lite driver.

I have two chips on the same i2c bus with different addresses.

I have two programs, program A talks to one chip and program B talks to the other.

If I run each program on it's own then everything is fine. If I run both programs together then occasionally one of the programs will return rubbish and/or error codes.

Both programs open /dev/i2c-0 read/write. No errors returned at this point, so I somehow assumed that the driver would or could handle multiple requests on the same bus for different chips, holding off one read/write request if anything was in progress. This doesn't seem to happen.

Should the driver hold off one request if another is in progress ? Or is there some option I've overlooked somewhere to implement this ?

No-one knows I guess.

probably overkill but I've now implemented my own front end to the driver using semaphores to make sure only one i/o request is current at a time.