On Tue, Aug 29, 2023 at 12:14:44PM +0100, Robin Murphy wrote: > dma_get_max_seg_size() represents a capability of the device itself, namely > the largest contiguous range it can be programmed to access in a single DMA > descriptor/register/whatever. Yes. In a way it's a bit odd that it ended up in a field in struct device, as the feature might actually be different for different DMA engines or features in a device. If I was to redesign it from scratch I'd just pass it to dma_map_sg. >> Generally looking at videobuf2-dma-sg, I feel like we would benefit >> from some kind of dma_alloc_table_from_pages() that simply takes the >> struct dev pointer and does everything necessary. > > Possibly; this code already looks lifted from drm_prime_pages_to_sg(), and > if it's needed here then presumably vb2_dma_sg_get_userptr() also needs it, > at the very least. Yes, there's tons of them. But I'd feel really bad adding even more struct scatterlist based APIs given how bad of a data structure that is.
