On Mon, Jun 28, 2021 at 09:27:05AM +0000, Roberto Sassu wrote: > > From: Greg KH [mailto:gregkh@xxxxxxxxxxxxxxxxxxx] > > Sent: Monday, June 28, 2021 10:46 AM > > On Mon, Jun 28, 2021 at 08:30:32AM +0000, Roberto Sassu wrote: > > > > > +struct compact_list_hdr { > > > > > + __u8 version; > > > > > > > > You should never need a version, that way lies madness. > > > > > > We wanted to have a way to switch to a new format, if necessary. > > > > Then just add a new ioctl if you need that in the future, no need to try > > to cram it into this one. > > Given that digest lists are generated elsewhere, it would be still > unclear when the ioctl() would be issued. Maybe the kernel needs > to parse both v1 and v2 digest lists (I expect that v1 cannot be easily > converted to v2, if they are signed). > > It would be also unpractical if digest lists are loaded at kernel > initialization time (I didn't send the patch yet). Then that is up to your api design, I do not know. But note that "version" fields almost always never work, so be careful about assuming that this will solve any future issues. > > > > > + __le16 type; > > > > > + __le16 modifiers; > > > > > + __le16 algo; > > > > > + __le32 count; > > > > > + __le32 datalen; > > > > > > > > Why are user/kernel apis specified in little endian format? Why would > > > > that matter? Shouldn't they just be "native" endian? > > > > > > I thought this would make it clear that the kernel always expects the > > > digest lists to be in little endian. > > > > Why would a big endian system expect the data from userspace to be in > > little endian? Shouldn't this always just be "native" endian given that > > this is not something that is being sent to hardware? > > The digest list might come from a system with different endianness. Ok, I have no idea what digests really are used for then. So stick with little endian and be sure to properly convert within the kernel as needed. thanks, greg k-h
