On Tue, Mar 12, 2019 at 2:46 AM Wolfram Sang <wsa@xxxxxxxxxxxxx> wrote: > > > > How about also printing some warning if threshold is zero? Since > > Hmm, not a warning because a user of a kernel can't do much about it. A > debug might make sense; it is for developers and will be compiled away > for production use. > > > caller might expect that if msg->len >= threshold, they will get valid > > pointer. But they will get valid pointer if (msg->len, threshold) is > > (>0, 0) and NULL if (=0, 0). So warn them that the threshold is bogus. > > Well, callers should always check for NULL because a valid pointer can > not be guaranteed (ENOMEM case). And I still don't get why would you > want a valid DMA-able pointer if the msg length is 0? Yes. But I think the debug message here is just to tell caller that threshold == 0 might not make sense. For threshold > 0, msg->len >= threshold returns valid. But it's not the case when threshold is 0. Also, threshold is 0 and 1 behaves the same: msg->len == 0 returns NULL, msg->len > 0 returns valid. > > Thanks! > > -----BEGIN PGP SIGNATURE----- > > iQIzBAABCAAdFiEEOZGx6rniZ1Gk92RdFA3kzBSgKbYFAlyGrQIACgkQFA3kzBSg > Kbb61Q//XZoT6dJYvO2WdyhYQf2Zpb4S1JEwSkMxa1XRQmw4caIdOLyJVt+OPzFo > 6Swbg0GQbFPV0tagj9VRTTWWTA6biRf69t+d5fNCMFWJ4Rx89CuJvy1EOA6A8LHN > Ckce/8HUXJAFdIaMwlkCagwepfO3WJ7GYDrGxiOM9e8cCOGkNgw/bXe3Xks2rcgC > 8eFiUGqDrrG3LwsTlqBfjBC1aErwYgC/QBO0uhWiodkszggEV8T1D9ykbfTSOvCr > LHZro3jzmR8E+K1zsujXuP2eDAhaN5V1s7VNI2mrzsQcxl/v7YKd17Us5Iqzq/1d > 4Ynv0gr7kTLoq5wOv5gamESXQ+m8PBmU7gikrIBh7ie0HXXyQY1U7sO5iSwBoMwC > eMegBAK8IDr5qM2YAb+urQQ/w7NdA731cYpm0+srfVSsxdpCvWJSROXHjRcrBzkm > xkw9fY0s5l5hWzWtjrOocYVd68MOmj6hnVFW6n9itAuRsi7CZJ4UnxxpcCbBgfEQ > +fhru8D6Ie1VkUtLtQlNFh61KJDTZ1Sg2YisL1M1N/nRAH22pSaMxyX2kpXsZI7f > WsCVIj3Rgow6vOqqUa85aYOqcyWllO29AMTMu+srAbfUWTIZ6iTtB5Dz5bC9oUPN > YyfviJYySO6UocuuZH1AAmvPdoqlly11ouTiA69vlPIx0hW8o9U= > =ZJU8 > -----END PGP SIGNATURE-----
