Re: [PATCH] drm/xlnx/zynqmp-dpsub: Fix dependencies for COMPILE_TEST

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Apr 10, 2026 at 05:08:00PM +0800, Chen-Yu Tsai wrote:
> On Fri, Apr 10, 2026 at 4:49 PM Tomi Valkeinen
> <tomi.valkeinen@ideasonboard.com> wrote:
> >
> > Hi,
> >
> > On 08/04/2026 11:14, Chen-Yu Tsai wrote:
> > > The zynqmp-dpsub driver does not have build time dependencies on the PHY
> > > or DMA drivers. These are runtime hardware restrictions.
> > >
> > > Group the two dependencies with ARCH_ZYNQMP so that the driver can be
> > > compile tested without them.
> > >
> > > Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
> > > ---
> > > IMO the two driver dependencies could be removed altogether, but that
> > > would be up to the driver and platform maintainers.
> > > ---
> > >   drivers/gpu/drm/xlnx/Kconfig | 4 +---
> > >   1 file changed, 1 insertion(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/xlnx/Kconfig b/drivers/gpu/drm/xlnx/Kconfig
> > > index cfabf5e2a0bb..4c6729459f40 100644
> > > --- a/drivers/gpu/drm/xlnx/Kconfig
> > > +++ b/drivers/gpu/drm/xlnx/Kconfig
> > > @@ -1,10 +1,8 @@
> > >   config DRM_ZYNQMP_DPSUB
> > >       tristate "ZynqMP DisplayPort Controller Driver"
> > > -     depends on ARCH_ZYNQMP || COMPILE_TEST
> > > +     depends on (ARCH_ZYNQMP && PHY_XILINX_ZYNQMP && XILINX_ZYNQMP_DPDMA) || COMPILE_TEST
> > >       depends on COMMON_CLK && DRM && OF
> > >       depends on DMADEVICES
> > > -     depends on PHY_XILINX_ZYNQMP
> > > -     depends on XILINX_ZYNQMP_DPDMA
> > >       select DMA_ENGINE
> > >       select DRM_CLIENT_SELECTION
> > >       select DRM_DISPLAY_DP_HELPER
> >
> > I think the above looks more difficult to understand than the current
> > version. We should perhaps rather drop the dependencies. But if we go
> > that way, then... we can also drop DMADEVICES, DMA_ENGINE, GENERIC_PHY
> > at least.
> 
> Perhaps. All the APIs for these are properly stubbed, so I guess
> they also count as runtime dependencies.
> 
> > What problem does this solve? Why are these two dependencies bad for
> > compile testing, but the other dependencies/selects are ok?
> 
> I was build testing changes across multiple DRM drivers in addition to
> the main platform I work on. Having to find and select each dependency
> was annoying.

I've had the same experience. It's really hard to do drm subsystem
wide changes, and be sure that all the code being touched is actually
getting compiled.

> 
> I would say DMADEVICES and GENERIC_PHY are much more common to embedded
> devices than SoC specific drivers.
> 
> > I personally don't mind hard runtime dependencies expressed in the
> > Kconfig, as searching for the correct dependency-drivers when your
> > driver doesn't probe is always a PITA.
> 
> I don't mind it either. But the way they are described means that compile
> testing is overly dependent on having some other platform specific
> driver enabled.

If only "select" worked in a sane way :/ Although that would still
force you to actually compile all the runtime dependencies, making
the build slower.

> 
> 
> I suppose another way to write this would be:
> 
>     depends on ARCH_ZYNQMP if !COMPILE_TEST
>     depends on PHY_XILINX_ZYNQMP if !COMPILE_TEST
>     depends on XILINX_ZYNQMP_DPDMA if !COMPILE_TEST

I believe the ||COMPILE_TEST pattern is much more common.

>     ...
> 
> Does that work for you?
> 
> 
> Thanks
> ChenYu

-- 
Ville Syrjälä
Intel