Re: [PATCH 1/9] dmaengine: Support bus widths of 32 bytes and above

[Jonathan Cameron <jic23@kernel.org>]

On Sat, 1 Aug 2026 03:42:22 +0100
Jonathan Cameron <jic23@kernel.org> wrote:

> On Thu, 30 Jul 2026 14:16:30 -0500
> Frank Li <Frank.li@oss.nxp.com> wrote:
> 
> > On Thu, Jul 30, 2026 at 03:23:08PM +0100, Nuno Sá via B4 Relay wrote:  
> > > [You don't often get email from devnull+nuno.sa.analog.com@kernel.org. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> > >
> > > From: Nuno Sá <nuno.sa@analog.com>
> > >
> > > The src_addr_widths and dst_addr_widths capability masks encode each
> > > supported width as a bit whose position equals the corresponding
> > > enum dma_slave_buswidth value (e.g. DMA_SLAVE_BUSWIDTH_4_BYTES sets bit
> > > 4). As these masks are plain u32, widths of 32 bytes and above
> > > (DMA_SLAVE_BUSWIDTH_32/64/128_BYTES map to bits 32, 64 and 128) cannot
> > > be represented at all.
> > >
> > > Introduce bitmap-based bus width capabilities that span the full enum
> > > range. To allow DMA controller producers to be converted incrementally,
> > > keep the legacy dma_device u32 fields alongside the new bitmaps:
> > > producers using the new helpers populate the bitmap and mirror the low
> > > 32 bits back into the legacy field, while dma_get_slave_caps() folds a
> > > legacy-only producer's u32 into the returned bitmap.
> > >
> > > Add helpers for producers and consumers so users do not need to depend
> > > on the bitmap layout directly. Once the remaining producers are
> > > converted, the legacy dma_device u32 fields can be dropped.
> > >
> > > Signed-off-by: Nuno Sá <nuno.sa@analog.com>
> > > ---    
> > 
> > Reviewed-by: Frank Li <Frank.Li@nxp.com>  
> https://sashiko.dev/#/patchset/20260730-dmaengine-support-wider-dma-masks-v1-0-3732f1f9d9ca%40analog.com 
> has a comment on this that smells plausible at least.
> Looks like the stm32 driver modifies dst_bus_widths in it's device_caps()
> callback.
Reading on, you fix it later in series.

This is going to break bisection on that device, but not build
so I guess maybe fair enough to do it in this sequence.

J
> 
> Jonathan
>