Hi Daniel, On 01/20/2015 06:50 PM, Daniel Mack wrote: > Hi Michael, > > Thanks a lot for for intense review of the documentation. Much appreciated. > > I've addressed all but the below issues, following your suggestions. Are your changes already visible somewhere? > On 01/20/2015 02:58 PM, Michael Kerrisk (man-pages) wrote: >>> + and KDBUS_CMD_ENDPOINT_MAKE (see above). >>> + >>> + Following items are expected for KDBUS_CMD_BUS_MAKE: >>> + KDBUS_ITEM_MAKE_NAME >>> + Contains a string to identify the bus name. >> >> So, up to here, I've seen no definition of 'kdbus_item', which leaves me >> asking questions like: what subfield is KDBUS_ITEM_MAKE_NAME stored in? >> which subfield holds the pointer to the string? >> >> Somewhere earlier, kdbus_item needs to be exaplained in more detail, >> I think. > > Hmm, you're quoting text from section 5, and section 4 actually > describes the concept of items quite well I believe? Well, Section 4 is pretty short. My point is that most of the various blob formats (e.g., kdbus_pids, kdbus_caps, kdbus_memfd) are not documented in kdbus.txt. They all should be, IMO. >>> + __s64 priority; >>> + With KDBUS_RECV_USE_PRIORITY set in flags, receive the next message in >>> + the queue with at least the given priority. If no such message is waiting >>> + in the queue, -ENOMSG is returned. >> >> ### >> How do I simply select the highest priority message, without knowing what >> its priority is? > > The wording is indeed unclear here. KDBUS_RECV_USE_PRIORITY causes the > messages to be dequeued by their priority. The 'priority' field is > simply a filter that request a minimum priority. By setting this field > to the highest possible value, you effectively bypass the filter. I've > added a better description now. Thanks for the clarification. >>> + -ENOMEM The kernel memory is exhausted >>> + -ENOTTY Illegal ioctl command issued for the file descriptor >> >> Why ENOTTY here, rather than EINVAL? The latter is, I beleive, the usual >> ioctl() error for invalid commands, I believe (If you keep ENOTTY, add an >> explanation in this document.) > > Hmm, no. -ENOTTY is commonly used as return code when calling ioctls > that can't be handled by the FDs they're called on. 'man errno(3)' even > states: "ENOTTY Inappropriate I/O control operation (POSIX.1)". Okay. >>> + -EINVAL Unsupported item attached to command >>> + >>> +For all ioctls that carry a struct as payload: >>> + >>> + -EFAULT The supplied data pointer was not 64-bit aligned, or was >>> + inaccessible from the kernel side. >>> + -EINVAL The size inside the supplied struct was smaller than expected >>> + -EMSGSIZE The size inside the supplied struct was bigger than expected >> >> Why two different errors for smaller and larger than expected? (If you keep things this >> way, pelase explain the reason in this document.) > > Providing a struct that is smaller than the minimum doesn't give the > ioctl a valid set of information to process the request. Hence, I think > -EINVAL is appropriate. However, -EMSGSIZE is something that users might > hit when they make message payloads too big, and I think it's good to > have a change to distinguish the two cases in error handling. I added > something in the document now. Thanks. > Again, thanks a lot for reading the documentation so accurately! You're welcome. Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
