i2c acces threadsafe ?

[oklitz]

Hi !

I dont know.... or i'm not really sure if the i2c acces is threadsafe

Heres my problem:

process 1:

ioctl(fd, I2C_SLAVE, DEVICE_1_ADDR)
...
byte = i2c_smbus_read_byte_data(fd, reg);

at the same time:

process 2:

ioctl(fd, I2C_SLAVE, DEVICE_2_ADDR)
...
byte = i2c_smbus_read_byte_data(fd, reg);

What if process 2 is running after the ioctl which sets the slave adress of process 1?
When this is safe, because of different fd's (perhaps i dont know) , what if this are two threads with the same fd ?
Should i protect i2c acces with semaphores or mutexes ?

I want to make *REALLY* sure that i can have multiple threads and processes accessing multiple slave devices
at the same time.
I don't know how the i2c access is implementet in the kernel.

Can anybody tell me please something about it or point to some docs/links ?

mfg Marco Oklitz

[oklitz]

Ok its bound to the fd
I have tested it with a process forking and using the same fd -> didnt work
I have to call open in every thread or process then it worked fine

[crashmaster]

$this->bbcode_second_pass_quote('oklitz', '
')I have to call open in every thread or process then it worked fine