On Wed, 2021-07-21 at 02:37 +0000, Joel Stanley wrote: > On Fri, 16 Jul 2021 at 15:19, Eddie James <eajames@xxxxxxxxxxxxx> > wrote: > > Set and increment the sequence number during the submit operation. > > This prevents sequence number conflicts between different users of > > the interface. A sequence number conflict may result in a user > > getting an OCC response meant for a different command. Since the > > sequence number is now modified, the checksum must be calculated > > and > > set before submitting the command. > > > > Signed-off-by: Eddie James <eajames@xxxxxxxxxxxxx> > > Reviewed-by: Joel Stanley <joel@xxxxxxxxx> > > > @@ -479,11 +483,26 @@ int fsi_occ_submit(struct device *dev, const > > void *request, size_t req_len, > > return -EINVAL; > > } > > > > + /* Checksum the request, ignoring first byte (sequence > > number). */ > > + for (i = 1; i < req_len - 2; ++i) > > + checksum += byte_request[i]; > > + > > This could go below, after you've got the sequence number, so the > checksumming all happens in the same spot? It definitely could, I had the idea to do the checksumming outside the mutex in case it took a long time? Probably not worth it though. > > The driver has become a bit of a maze, I can't tell how you're > deciding what goes in fsi_occ_submit vs occ_write vs occ_putsram. If > oyu have some ideas on how to simplify it then I would welcome those > changes. Well, it doesn't really matter in fsi_occ_submit vs occ_putsram, as the latter is only called in the former. occ_write wouldn't be used by the hwmon interface, which is why we're moving some of that to fsi_occ_submit, to have more in common. Agree it could probably be organized better but I don't immediately have a good idea how to do that. Thanks for the review! Eddie > > > > > mutex_lock(&occ->occ_lock); > > > > - /* Extract the seq_no from the command (first byte) */ > > - seq_no = *(const u8 *)request; > > - rc = occ_putsram(occ, request, req_len); > > + /* > > + * Get a sequence number and update the counter. Avoid a > > sequence > > + * number of 0 which would pass the response check below > > even if the > > + * OCC response is uninitialized. Any sequence number the > > user is > > + * trying to send is overwritten since this function is the > > only common > > + * interface to the OCC and therefore the only place we can > > guarantee > > + * unique sequence numbers. > > + */ > > + seq_no = occ->sequence_number++; > > + if (!occ->sequence_number) > > + occ->sequence_number = 1; > > + checksum += seq_no; > > + > > + rc = occ_putsram(occ, request, req_len, seq_no, checksum); > > if (rc) > > goto done;
