Re: [PATCH v3 0/9] dmaengine: Support bus widths of 32 bytes and above

[Andy Shevchenko]

On Mon, Aug 31, 2026 at 12:46:37PM +0100, Nuno Sá wrote:
> The DMA engine slave capabilities advertise the supported source and
> destination bus widths through src_addr_widths / dst_addr_widths. These
> are plain u32 bitmasks where a set bit's position equals the
> corresponding enum dma_slave_buswidth value, e.g.
> DMA_SLAVE_BUSWIDTH_4_BYTES sets bit 4.
> 
> The consequence is that widths of 32 bytes and above cannot be
> represented at all: DMA_SLAVE_BUSWIDTH_32/64/128_BYTES would need bits
> 32, 64 and 128, which do not fit in a u32. Hardware with wider data
> paths is becoming common, so add a representation that can express these
> widths while still using enum dma_slave_buswidth.
> 
> This series switches consumers and a small set of producers to the new
> bus width capabilities, represented by a dma_buswidth_mask_t modeled
> after dma_cap_mask_t. The legacy dma_device u32 fields are kept for now
> so the remaining DMA controller drivers can be converted incrementally:
> dma_async_device_register() folds a legacy-only producer's u32 into the
> mask, so consumers only ever have to look at the mask.
> 
> The new interface lives in include/linux/dma/engine/{types,widthmask}.h
> rather than in linux/dmaengine.h, so that only its users pay for the
> linux/bitmap.h include. Every accessor takes a dma_buswidth_mask_t,
> which means the interface will not change when the legacy fields are
> eventually dropped.
> 
> Once the remaining producers are converted, the legacy dma_device
> src/dst_addr_widths fields can be removed as a final cleanup.
> 
> This issue was discussed before here:
> 
> https://lore.kernel.org/dmaengine/abkoXXbaxaiqbBuX@vaman/

Thanks, this version looks like the right approach. I have looked at a couple
of patches and only the first one needs a bit of work, the rest looks nice!

-- 
With Best Regards,
Andy Shevchenko