On Thu, Jan 30, 2020 at 11:31 AM Jens Axboe <axboe@xxxxxxxxx> wrote: > > On 1/30/20 9:29 AM, Glauber Costa wrote: > > On Thu, Jan 30, 2020 at 11:13 AM Jens Axboe <axboe@xxxxxxxxx> wrote: > >> > >> On 1/30/20 9:00 AM, Glauber Costa wrote: > >>> It is common for an application using an ever-evolving interface to want > >>> to inquire about the presence of certain functionality it plans to use. > >>> > >>> Information about opcodes is stored in a io_uring_probe structure. There > >>> is usually some boilerplate involved in initializing one, and then using > >>> it to check if it is enabled. > >>> > >>> This patch adds two new helper functions: one that returns a pointer to > >>> a io_uring_probe (or null if it probe is not available), and another one > >>> that given a probe checks if the opcode is supported. > >> > >> This looks good, I committed it with minor changes. > >> > >> On top of this, we should have a helper that doesn't need a ring. So > >> basically one that just sets up a ring, calls io_uring_get_probe(), > >> then tears down the ring. > >> > > I'd be happy to follow up with that. > > > > Just to be sure, the information returned by probe should be able to outlive the > > tear down of the ring, right ? > > Yeah, same lifetime as the helper you have now, caller must free it once > done. Well, in hindsight, I should have called that io_uring_get_probe_ring() so io_uring_get_probe() doesn't take a ring. Alternatively, to keep things in a single function, I can change io_uring_get_probe() so that if it ring is NULL, we do our own allocation. I actually kind of like that. Would that work for you ? > > -- > Jens Axboe >
