drm-legacy-kmod vs. drm-kmod

[Warner Losh]

On Tue, Mar 10, 2020 at 1:08 PM Greg V <greg at unrelenting.technology> wrote:

>
>
> Mar 10, 2020 8:04:21 PM Robert Huff <roberthuff at rcn.com>:
>
> > > > I have an older machine with an on-board ATI Radeon HD3300.
> > >
> > > Have you tried modern radeonkms on it (from drm-kmod not legacy)?
> >
> > I have not; existing information strongly suggests that will not
> > work.
>
> Always try everything yourself! It's not that hard.
>
>
> > > > According to the "FreeBSD Graphics Blog" on github, that line
> > > > (for AMD) is the HD7000 (family) chipset.
> > >
> > > "HD7000 family" is kind of a meaningless marketing term: it includes
> > > TeraScale 2, GCN 1 and GCN 2.
> > >
> >
> > I'm only quoting the blog. :-(
> > <does further quick research>
> > Let's assume for the moment I'm talking about the HD7730 and
> > higher.
> > This is not about increased hardware performance; the old chip
> > did just fine for that system. It's about having the hardware to
> > support the software that's in active development.
>
> radeonkms is still supported – so everything R600, from the earliest HD
> something to the R5 ones, should work.
>
> Active *development* is happening on GCN GPUs supported by amdgpu.
>
>
> Keep in mind that our "legacy" port is.. well.. legacy *in terms of
> porting*. It's manually ported instead of writing a compatibility layer
> which is how the current port works.
> The legacy port is stuck on older Linux code because of that, but *Linux
> did not drop support for older GPUs in the same drivers* so the new port
> should work just as well.
>

It's also legacy in terms of the APIs it uses. This means that over time
other things will shift away from those APIs (as happened with
xf86-ati-video-legacy port) and as that happens, support for it will
diminish and eventually go away. That's much less likely to happen with the
amdgpu driver.

Warner