On Wed, Oct 30, 2019 at 05:18:25PM -0500, Rob Herring wrote: > On Wed, Oct 30, 2019 at 9:56 AM Lorenzo Pieralisi > <lorenzo.pieralisi@xxxxxxx> wrote: > > > > On Wed, Oct 30, 2019 at 12:49:59PM +0000, Robin Murphy wrote: > > > On 30/10/2019 11:48, Lorenzo Pieralisi wrote: > > > > [+Cc Robin] > > > > > > > > On Wed, Oct 30, 2019 at 12:14:54PM +0530, Srinath Mannam wrote: > > > > > Hi Lorenzo, > > > > > > > > > > Thanks for the details. > > > > > Based on Robin's comment in the old patch, I thought dma_ranges list > > > > > will be in sorted order. > > > > > https://lore.kernel.org/lkml/741a4210-251c-9c00-d4a7-bc7ebf8cd57b@xxxxxxx/ > > > > > > > > > > Now, another patch is required to sort the list before reserving in > > > > > iova_reserve_pci_windows() function. > > > > > > > > > > Regards, > > > > > Srinath. > > > > > > > > Don't top-post please. > > > > > > > > https://en.wikipedia.org/wiki/Posting_style#Top-posting > > > > > > > > Yes, the dma_ranges list must be sorted somehow I reckon > > > > iova_reserve_pci_windows() is where it should be done (since that's > > > > where the requirement is) or it can be done in > > > > devm_of_pci_get_host_bridge_resources(). > > > > > > > > Thoughts ? > > > > > > Right, strictly it's only iova_reserve_pci_windows() that needs the list > > > sorted, it just worked out that maintaining the list in sorted order by > > > construction took a fair bit less code than explicitly sorting it. In terms > > > of preserving that behaviour in a slightly more generalised fashion I > > > suppose we could add something like: > > > > > > void pci_add_resource_offset_sorted(struct list_head *resources, > > > struct resource *res, > > > resource_size_t offset) > > > { > > > struct resource_entry *entry; > > > > > > resource_list_for_each_entry(entry, resources) > > > if (entry->res.start > res.start) > > > break; > > > > > > pci_add_resource_offset(&entry->node, res, offset); > > > } > > > > > > but if you'd rather add a specific resource_list_sort() or even just > > > open-code it in iommu-dma, I don't have any real preference. The "least code > > > necessary" approach definitely made sense when individual drivers were > > > expected to build their own lists, but once it gets generalised then having > > > a sensible and robust API becomes a more important consideration. > > > > I think that open coding it in iommu-dma is fine, @RobH would you be > > able to add this to the series please ? I think it should be added to > > prevent any regressions, we can't rely on dma-ranges entries order in DT > > files. > > I don't think it's good to be modifying the list as a side effect of > calling iova_reserve_pci_windows() and making a copy of it wouldn't be > great either. So I'm just going to keep it sorted in > devm_of_pci_get_host_bridge_resources(). Yes I thought about that - that's the most reasonable approach I think. Thanks, Lorenzo
