On Wed, Jan 01, 2025 at 07:46:41PM -0800, Bart Van Assche wrote: > On 1/1/25 6:49 PM, Ming Lei wrote: > > On Wed, Jan 01, 2025 at 06:30:30PM -0800, Bart Van Assche wrote: > > > Additionally, this patch looks wrong to me. There are good reasons why the > > > block layer requires that the DMA segment size is at least as large > > > as the page size. > > > > Do you think 512byte sector can't be DMAed? > > A clarification: I was referring to the maximum DMA segment size. The > 512 byte number in your email refers to the actual DMA transfer size. My > statement does not apply to the actual DMA transfer size. But why does DMA segment size have to be >= PAGE_SIZE(4KB, 64KB)? I don't think that the constraint is from hardware because DMA controller is capable of doing DMA on buffer with smaller alignment & size. IMO, the limit is actually from block layer, that is why I posted out this patch. > > > > You may want to take a look at this rejected patch series: > > > Bart Van Assche, "PATCH v6 0/8] Support limits below the page size", > > > June 2023 (https://lore.kernel.org/linux-block/20230612203314.17820-1-bvanassche@xxxxxxx/). > > > > '502 Bad Gateway' is returned for the above link. > > That link works fine here on multiple devices (laptop, workstation, > smartphone) so please check your setup. It is reachable now.
