On Wed, Oct 21, 2015 at 08:23:41PM -0700, Randy Dunlap wrote: > Hi, > > Some corrections and a few questions... Thanks for the corrections. Answer below. > On 10/21/15 14:00, Jérôme Glisse wrote: > > This add documentation on how HMM works and a more in depth view of how it > > should be use by device driver writers. > > > > Signed-off-by: Jérôme Glisse <jglisse@xxxxxxxxxx> [...] > > +synchronizing device page table for range that the device driver explicitly ask > > ranges asks > > or is only one range supported? Several ranges are supported. [...] > > + /* Mirror memory (in read mode) between addressA and addressB */ > > + your_hmm_event->hmm_event.start = addressA; > > + your_hmm_event->hmm_event.end = addressB; > > Multiple events (ranges) can be specified? Device driver have to make one call per range but multiple threads can make concurrent call for different ranges. > Is hmm_event.end (addressB) included or excluded from the range? Forgot to copy comment from header file, start is inclusive, end is exclusive. [...] > > + struct hmm_pt_iter iter; > > + hmm_pt_iter_init(&iter, &mirror->pt) > > + > > + /* Get pointer to HMM page table entry for a given address. */ > > + dma_addr_t *hmm_pte; > > + hmm_pte = hmm_pt_iter_walk(&iter, &addr, &next); > > what are 'addr' and 'next'? (types) unsigned long will add then to the doc, good point. [...] > > + /* Migrate system memory between addressA and addressB to device memory. */ > > + your_hmm_event->hmm_event.start = addressA; > > + your_hmm_event->hmm_event.end = addressB; > > is hmm_event.end (addressB) inclusive and exclusive? > i.e., is it end_of_copy + 1? > i.e., is the size of the copy addressB - addressA or > addressB - addressA + 1? > i.e., is addressB = addressA + size > or is addressB = addressA + size - 1 Exclusive last one. > In my experience it is usually better to have a start_address and size > instead of start_address and end_address. I switched several time btw the 2 offer differents version of the patchset, it is something that can be change down the road unless you have strong feeling about it. Cheers, Jérôme -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>