RE: [PATCH 1/1] Documentation/core-api: Add swiotlb documentation

[Michael Kelley]

From: Matthew Wilcox <willy@xxxxxxxxxxxxx> Sent: Thursday, April 18, 2024 7:29 AM

> 
> On Thu, Apr 18, 2024 at 06:52:13AM -0700, mhkelley58@xxxxxxxxx wrote:
> > There's currently no documentation for the swiotlb. Add documentation
> > describing usage scenarios, the key APIs, and implementation details.
> > Group the new documentation with other DMA-related documentation.
> 
> This is really well written.  Thank you.  One minor nit below.
> 
> > +Usage Scenarios
> > +---------------
> > +The swiotlb was originally created to handle DMA for devices
> > +with addressing limitations. As physical memory sizes grew
> > +beyond 4 Gbytes, some devices could only provide 32-bit DMA
> > +addresses. By allocating bounce buffer memory below the 4 Gbyte
> 
> I'd prefer GiB to Gbytes; we might also prefer GB, Gigabyte or Gibibyte,
> but Gbytes seems wrong.

Good point.  I'll update sizes throughout to use the correct terminology.

Michael

> 
> You've written a lot here, and I'm not an expert on swiommu, but nothing
> else leapt out at me.