On 2018-05-10 13:16, Wolfram Sang wrote: > On Sat, May 05, 2018 at 08:02:21AM -0500, Wenwen Wang wrote: >> In i2c_smbus_xfer_emulated(), the function i2c_transfer() is invoked to >> transfer i2c messages. The number of actual transferred messages is >> returned and saved to 'status'. If 'status' is negative, that means an >> error occurred during the transfer process. In that case, the value of >> 'status' is an error code to indicate the reason of the transfer failure. >> In most cases, i2c_transfer() can transfer 'num' messages with no error. >> And so 'status' == 'num'. However, due to unexpected errors, it is probable >> that only partial messages are transferred by i2c_transfer(). As a result, >> 'status' != 'num'. This special case is not checked after the invocation of >> i2c_transfer() and can potentially lead to unexpected issues in the >> following execution since it is expected that 'status' == 'num'. >> >> This patch checks the return value of i2c_transfer() and returns an error >> code -EIO if the number of actual transferred messages 'status' is not >> equal to 'num'. >> >> Signed-off-by: Wenwen Wang <wang6495@xxxxxxx> > > Applied to for-current, thanks! > I meant to comment here but got side-tracked and never got around to it. But see e.g. [1] and [2] for drivers that will not be happy with this change. Maybe there are more of those? I did a scan of the drivers in algos/ and busses/, but there are drivers all over the tree that implements .master_xfer that I have not audited. Who knows what further problems this patch will reveal? So, maybe we should be a bit conservative and only WARN as a first step? Yes, I know that I suggested this, sorry for not following up with this in a more timely fashion... Cheers, Peter [1] https://lkml.org/lkml/2018/5/9/871 [2] https://lkml.org/lkml/2018/5/9/877 PS. Also busses/i2c-rcar.c seems like it might return a short "success" for some sequence of events. But I'm not sure about that one...
