Re: [PATCH 8/9] drm/rockchip: Drop ROCKCHIP_IOMMU depend for DRM_ROCKCHIP

["Heiko Stübner" <heiko@sntech.de>]

Hi,

Am Freitag, 9. Januar 2026, 02:26:00 Mitteleuropäische Normalzeit schrieb Chaoyi Chen:
> On 1/9/2026 3:03 AM, Heiko Stuebner wrote:
> > Am Donnerstag, 6. November 2025, 03:06:31 Mitteleuropäische Normalzeit schrieb Chaoyi Chen:
> >> From: Chaoyi Chen <chaoyi.chen@rock-chips.com>
> >>
> >> On the RK3506 platform, there is no iommu hardware. And even on
> >> platform that have iommu hardware, it should be possible to use
> >> VOP without enabling iommu. In this case, a contiguous memory
> >> space like CMA should be used.
> >>
> >> So this patch removes the dependency on ROCKCHIP_IOMMU.
> >>
> >> Signed-off-by: Chaoyi Chen <chaoyi.chen@rock-chips.com>
> >> ---
> >>  drivers/gpu/drm/rockchip/Kconfig | 3 ++-
> >>  1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/rockchip/Kconfig b/drivers/gpu/drm/rockchip/Kconfig
> >> index b7b025814e72..a056d419190c 100644
> >> --- a/drivers/gpu/drm/rockchip/Kconfig
> >> +++ b/drivers/gpu/drm/rockchip/Kconfig
> >> @@ -1,7 +1,8 @@
> >>  # SPDX-License-Identifier: GPL-2.0-only
> >>  config DRM_ROCKCHIP
> >>  	tristate "DRM Support for Rockchip"
> >> -	depends on DRM && ROCKCHIP_IOMMU
> >> +	depends on DRM
> >> +	depends on ROCKCHIP_IOMMU || !ROCKCHIP_IOMMU
> > 
> > I don't really understand this yes+no line :-)
> > 
> > Can't you just
> > - drop the dependency altogether
> > or
> > - do a depends on ROCKCHIP_IOMMU if ARM64
> > 
> >
> 
> This trick is called optional-dependencies [0]. In addition to the 
> familiar depends on ROCKCHIP_IOMMU part, the newly added !ROCKCHIP_IOMMU
> ensures that DRM_ROCKCHIP can still be built even when ROCKCHIP_IOMMU
> is not build.
> 
> [0]: https://docs.kernel.org/kbuild/kconfig-language.html#optional-dependencies

thanks a lot for pointing me to this nifty feature :-)

Heiko