Hi Konrad, On Mon, Oct 31, 2016 at 6:52 PM, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote: > On Mon, Oct 31, 2016 at 04:45:04PM +0100, Geert Uytterhoeven wrote: >> On architectures like arm64, swiotlb is tied intimately to the core >> architecture DMA support. In addition, ZONE_DMA cannot be disabled. >> >> To aid debugging and catch devices not supporting DMA to memory outside >> the 32-bit address space, add a kernel command line option >> "swiotlb=nobounce", which disables the use of bounce buffers. >> If specified, trying to map memory that cannot be used with DMA will >> fail, and a warning will be printed (rate-limited). > > I would make the 'swiotlb_force' an enum. And then instead of this > being 'nobounce' just do the inverse of 'force', that is the > 'noforce' would trigger this no bounce effect. > > So: > > enum { > NORMAL, /* Default - depending on the hardware DMA mask and such. */ > FORCE, /* swiotlb=force */ > NO_FORCE, /* swiotlb=noforce */ Fine for me, but swiotlb_force is exported to platform code. Hence all users should be updated? Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds