Hi. A problem was found in my drivers. Before sending out patches, please let me ask a question to make sure the right fix. The problem is, my driver is forcibly setting STOP condition unless the next message is read. Please see this line: https://github.com/torvalds/linux/blob/v4.19-rc1/drivers/i2c/busses/i2c-uniphier-f.c#L405 Obviously, it it disturbing the I2C_RDWR ioctl functionality. Documentation/i2c/dev-interface says: ioctl(file, I2C_RDWR, struct i2c_rdwr_ioctl_data *msgset) Do combined read/write transaction without stop in between. So, I want to be sure what a driver should (or should not) do. A driver should issue STOP when and only when the I2C_M_STOP flag is set in msg->flags. Is this correct? In other words, do user-space programs need to explicitly set I2C_M_STOP where the STOP condition is desired? Then, another question popped up. User-space programs can send a single transaction with read() / write(). I2C_M_STOP is not set in this case. If a driver does not take care of the STOP condition at all, the I2C bus is never released. Is this the right thing to do? -- Best Regards Masahiro Yamada
