On 11/8/22 9:00 PM, Michał Mirosław wrote: >>>> + * @start: Starting address of the region >>>> + * @len: Length of the region (All the pages in this length are included) >>>> + * @vec: Address of page_region struct array for output >>>> + * @vec_len: Length of the page_region struct array >>>> + * @max_pages: Optional max return pages (It must be less than vec_len if specified) >>> I think we discussed that this is not counting the same things as >>> vec_len, so there should not be a reference between the two. The limit >>> is whatever fits under both conditions (IOW: n_vecs <= vec_len && >>> (!max_pages || n_pages <= max_pages). >> In worse case when pages cannot be folded into the page_region, the one >> page_region may have information of only one page. This is why I've >> compared them. I want to communicate to the user that if max_pages is >> used, the vec_len should be of equal or greater size (to cater worse >> case which can happen at any time). Otherwise in worse case, the api can >> return without finding the max_pages number of pages. I don't know how >> should I put this in the comment. > I'm not sure you need to, as this conclusion follows from the range vs > page distinction. > A user who wants to cater for the worst case will provide big-enough > `vec` array, but another, who might be memory-constrained, could > instead just retry the call with `start` updated to just after the > last returned page until the ioctl() returns less ranges than > `vec_len` allows. Makes sense. I'll update and send next revision. Thanks, Usama > > Best Regards > Michał Mirosław
