On Wed, May 20, 2020 at 10:03 AM Greg Kroah-Hartman <
gregkh@linuxfoundation.org> wrote:

> On Wed, May 20, 2020 at 09:50:36AM -0400, Jim Quinlan wrote:
> > On Wed, May 20, 2020 at 1:43 AM Greg Kroah-Hartman
> > <gregkh@linuxfoundation.org> wrote:
> > >
> > > On Tue, May 19, 2020 at 04:34:07PM -0400, Jim Quinlan wrote:
> > > > diff --git a/include/linux/device.h b/include/linux/device.h
> > > > index ac8e37cd716a..6cd916860b5f 100644
> > > > --- a/include/linux/device.h
> > > > +++ b/include/linux/device.h
> > > > @@ -493,6 +493,8 @@ struct dev_links_info {
> > > >   * @bus_dma_limit: Limit of an upstream bridge or bus which imposes
> a smaller
> > > >   *           DMA limit than the device itself supports.
> > > >   * @dma_pfn_offset: offset of DMA memory range relatively of RAM
> > > > + * @dma_map: Like dma_pfn_offset but used when there are multiple
> > > > + *           pfn offsets for multiple dma-ranges.
> > > >   * @dma_parms:       A low level driver may set these to teach
> IOMMU code about
> > > >   *           segment limitations.
> > > >   * @dma_pools:       Dma pools (if dma'ble device).
> > > > @@ -578,7 +580,12 @@ struct device {
> > > >                                            allocations such
> descriptors. */
> > > >       u64             bus_dma_limit;  /* upstream dma constraint */
> > > >       unsigned long   dma_pfn_offset;
> > > > -
> > > > +#ifdef CONFIG_DMA_PFN_OFFSET_MAP
> > > > +     const void *dma_offset_map;     /* Like dma_pfn_offset, but for
> > > > +                                      * the unlikely case of
> multiple
> > > > +                                      * offsets. If non-null,
> dma_pfn_offset
> > > > +                                      * will be 0. */
> > > > +#endif
> > > >       struct device_dma_parameters *dma_parms;
> > > >
> > > >       struct list_head        dma_pools;      /* dma pools (if
> dma'ble) */
> > >
> > > I'll defer to Christoph here, but I thought we were trying to get rid
> of
> > > stuff like this from struct device, not add new things to it for dma
> > Hi Greg,
> >
> > I wasn't aware of this policy.  I put it in 'struct device' because
> > just like the existing dma_pfn_offset; it seemed to be the only way to
> > pull this off.  I'll certainly follow any ideas on alternative
> > strategies from Christoph et al.
> >
> > > apis.  And why is it a void *?
> > Just wanted to minimize the number of lines I've added to device.h, no
> > other reason.
>
> How would using a real type make this more lines?  Never use a void *
> unless you have to, we want the compiler to check our errors for us :)
>

Got it; I did not need to define the struct in device.h.  Will fix if this
code makes it past v1 :-)

Jim



> thanks,
>
> greg k-h
>