On Mon Feb 19, 2024 at 8:29 PM UTC, Daniel P. Smith wrote: > On 2/1/24 17:49, Jarkko Sakkinen wrote: > > On Wed Jan 31, 2024 at 7:08 PM EET, Daniel P. Smith wrote: > >> The function tpm_tis_request_locality() is expected to return the locality > >> value that was requested, or a negative error code upon failure. If it is called > >> while locality_count of struct tis_data is non-zero, no actual locality request > >> will be sent. Because the ret variable is initially set to 0, the > >> locality_count will still get increased, and the function will return 0. For a > >> caller, this would indicate that locality 0 was successfully requested and not > >> the state changes just mentioned. > >> > >> Additionally, the function __tpm_tis_request_locality() provides inconsistent > >> error codes. It will provide either a failed IO write or a -1 should it have > >> timed out waiting for locality request to succeed. > >> > >> This commit changes __tpm_tis_request_locality() to return valid negative error > >> codes to reflect the reason it fails. It then adjusts the return value check in > >> tpm_tis_request_locality() to check for a non-negative return value before > >> incrementing locality_cout. In addition, the initial value of the ret value is > >> set to a negative error to ensure the check does not pass if > >> __tpm_tis_request_locality() is not called. > > > > This is way way too abtract explanation and since I don't honestly > > understand what I'm reading, the code changes look bunch of arbitrary > > changes with no sound logic as a whole. > > In more simpler terms, the interface is inconsistent with its return > values. To be specific, here are the sources for the possible values > tpm_tis_request_locality() will return: > 1. 0 - 4: _tpm_tis_request_locality() was able to set the locality > 2. 0: a locality already open, no locality request made > 3. -1: if timeout happens in __tpm_tis_request_locality() > 4. -EINVAL: unlikely, return by IO write for incorrect sized write > > As can easily be seen, tpm_tis_request_locality() will return 0 for both > a successful(1) and non-successful request(2). And to be explicit for > (2), if tpm_tis_request_locality is called for a non-zero locality and > the locality counter is not zero, it will return 0. Thus, making the > value 0 reflect as success when locality 0 is successfully requested and > as failure when a locality is requested with a locality already open. > > As for failures, correct me if I am wrong, but if a function is > returning negative error codes, it should not be using a hard coded -1 > as a generic error code. As I note, it is unlikely for the -EINVAL to be > delivered, but the code path is still available should something in the > future change the backing call logic. > > After this change, the possible return values for > tpm_tis_request_locality() become: > 1. 0 - 4: the locality that was successfully requested > 2. -EBUSY: tpm busy, unable to request locality > 3. -EINVAL: invalid parameter > > With this more consistent interface, I updated the return value checks > at the call sites to check for negative error as the means to catch > failures. For all commits: your responses to my queries have much more to the point information and buy-in than the original commit messages. So for next version I would take them and edit a bit and then this all makes much much more sense. Thank you. > > v/r, > dps BR, Jarkko
