linux-kernel - Re: [PATCH] drm/bridge: Select DRM_KMS_HELPER for DRM_PANEL

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Date: Mon, 18 Mar 2024 14:48:09 +0100
From: "Luca Weiss" <luca.weiss@...rphone.com>
To: "Jani Nikula" <jani.nikula@...ux.intel.com>, "Neil Armstrong"
 <neil.armstrong@...aro.org>, "Andrzej Hajda" <andrzej.hajda@...el.com>,
 "Robert Foss" <rfoss@...nel.org>, "Laurent Pinchart"
 <Laurent.pinchart@...asonboard.com>, "Jonas Karlman" <jonas@...boo.se>,
 "Jernej Skrabec" <jernej.skrabec@...il.com>, "Maarten Lankhorst"
 <maarten.lankhorst@...ux.intel.com>, "Maxime Ripard" <mripard@...nel.org>,
 "Thomas Zimmermann" <tzimmermann@...e.de>, "David Airlie"
 <airlied@...il.com>, "Daniel Vetter" <daniel@...ll.ch>
Cc: <~postmarketos/upstreaming@...ts.sr.ht>, <phone-devel@...r.kernel.org>,
 <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/bridge: Select DRM_KMS_HELPER for DRM_PANEL_BRIDGE

On Mon Mar 18, 2024 at 11:59 AM CET, Jani Nikula wrote:
> On Mon, 18 Mar 2024, Jani Nikula <jani.nikula@...ux.intel.com> wrote:
> > On Mon, 18 Mar 2024, Neil Armstrong <neil.armstrong@...aro.org> wrote:
> >> Hi,
> >>
> >> On Thu, 11 Jan 2024 13:38:04 +0100, Luca Weiss wrote:
> >>> Since the kconfig symbol of DRM_PANEL_BRIDGE is only adding
> >>> bridge/panel.o to drm_kms_helper object, we need to select
> >>> DRM_KMS_HELPER to make sure the file is actually getting built.
> >>> 
> >>> Otherwise with certain defconfigs e.g. devm_drm_of_get_bridge will not
> >>> be properly available:
> >>> 
> >>> [...]
> >>
> >> Thanks, Applied to https://gitlab.freedesktop.org/drm/misc/kernel.git (drm-misc-fixes)
> >>
> >> [1/1] drm/bridge: Select DRM_KMS_HELPER for DRM_PANEL_BRIDGE
> >>       https://gitlab.freedesktop.org/drm/misc/kernel/-/commit/e3f18b0dd1db242791afbc3bd173026163ce0ccc
> >
> > With my kernel config, e3f18b0dd1db ("drm/bridge: Select DRM_KMS_HELPER
> > for DRM_PANEL_BRIDGE") leads to:
> >
> > WARNING: unmet direct dependencies detected for DRM_KMS_HELPER
> >   Depends on [m]: HAS_IOMEM [=y] && DRM [=m]
> >   Selected by [y]:
> >   - DRM_PANEL_BRIDGE [=y] && HAS_IOMEM [=y] && DRM_BRIDGE [=y]
> >   Selected by [m]:
> >   - DRM [=m] && HAS_IOMEM [=y] && (AGP [=y] || AGP [=y]=n) && !EMULATED_CMPXCHG && HAS_DMA [=y] && DRM_FBDEV_EMULATION [=y]
> >   - DRM_MIPI_DBI [=m] && HAS_IOMEM [=y] && DRM [=m]
> >   - DRM_KUNIT_TEST [=m] && HAS_IOMEM [=y] && DRM [=m] && KUNIT [=y] && MMU [=y]
> >   - DRM_RADEON [=m] && HAS_IOMEM [=y] && DRM [=m] && PCI [=y] && MMU [=y] && (AGP [=y] || !AGP [=y])
> >   - DRM_AMDGPU [=m] && HAS_IOMEM [=y] && DRM [=m] && PCI [=y] && MMU [=y] && !UML
> >   - DRM_NOUVEAU [=m] && HAS_IOMEM [=y] && DRM [=m] && PCI [=y] && MMU [=y]
> >   - DRM_I915 [=m] && HAS_IOMEM [=y] && DRM [=m] && X86 [=y] && PCI [=y] && !PREEMPT_RT [=n]
> >   - DRM_XE [=m] && HAS_IOMEM [=y] && DRM [=m] && PCI [=y] && MMU [=y] && (m && MODULES [=y] || y && KUNIT [=y]=y) && 64BIT [=y]
> >   - DRM_VKMS [=m] && HAS_IOMEM [=y] && DRM [=m] && MMU [=y]
> >   - DRM_VMWGFX [=m] && HAS_IOMEM [=y] && DRM [=m] && PCI [=y] && MMU [=y] && (X86 [=y] || ARM64)
> >   - DRM_GMA500 [=m] && HAS_IOMEM [=y] && DRM [=m] && PCI [=y] && X86 [=y] && MMU [=y]
> >   - DRM_UDL [=m] && HAS_IOMEM [=y] && DRM [=m] && USB [=m] && USB_ARCH_HAS_HCD [=y] && MMU [=y]
> >   - DRM_AST [=m] && HAS_IOMEM [=y] && DRM [=m] && PCI [=y] && MMU [=y]
> >   - DRM_MGAG200 [=m] && HAS_IOMEM [=y] && DRM [=m] && PCI [=y] && MMU [=y]
> >   - DRM_QXL [=m] && HAS_IOMEM [=y] && DRM [=m] && PCI [=y] && MMU [=y]
> >   - DRM_VIRTIO_GPU [=m] && HAS_IOMEM [=y] && DRM [=m] && VIRTIO_MENU [=y] && MMU [=y]
> >   - DRM_BOCHS [=m] && HAS_IOMEM [=y] && DRM [=m] && PCI [=y] && MMU [=y]
> >   - DRM_CIRRUS_QEMU [=m] && HAS_IOMEM [=y] && DRM [=m] && PCI [=y] && MMU [=y]
> >   - DRM_GM12U320 [=m] && HAS_IOMEM [=y] && DRM [=m] && USB [=m] && MMU [=y]
> >   - DRM_PANEL_MIPI_DBI [=m] && HAS_IOMEM [=y] && DRM [=m] && SPI [=y]
> >   - DRM_SIMPLEDRM [=m] && HAS_IOMEM [=y] && DRM [=m] && MMU [=y]
> >   - TINYDRM_HX8357D [=m] && HAS_IOMEM [=y] && DRM [=m] && SPI [=y]
> >   - TINYDRM_ILI9163 [=m] && HAS_IOMEM [=y] && DRM [=m] && SPI [=y]
> >   - TINYDRM_ILI9225 [=m] && HAS_IOMEM [=y] && DRM [=m] && SPI [=y]
> >   - TINYDRM_ILI9341 [=m] && HAS_IOMEM [=y] && DRM [=m] && SPI [=y]
> >   - TINYDRM_ILI9486 [=m] && HAS_IOMEM [=y] && DRM [=m] && SPI [=y]
> >   - TINYDRM_MI0283QT [=m] && HAS_IOMEM [=y] && DRM [=m] && SPI [=y]
> >   - TINYDRM_REPAPER [=m] && HAS_IOMEM [=y] && DRM [=m] && SPI [=y]
> >   - TINYDRM_ST7586 [=m] && HAS_IOMEM [=y] && DRM [=m] && SPI [=y]
> >   - TINYDRM_ST7735R [=m] && HAS_IOMEM [=y] && DRM [=m] && SPI [=y]
> >   - DRM_XEN_FRONTEND [=m] && HAS_IOMEM [=y] && XEN [=y] && DRM [=m]
> >   - DRM_VBOXVIDEO [=m] && HAS_IOMEM [=y] && DRM [=m] && X86 [=y] && PCI [=y]
> >   - DRM_GUD [=m] && HAS_IOMEM [=y] && DRM [=m] && USB [=m] && MMU [=y]
> >   - DRM_SSD130X [=m] && HAS_IOMEM [=y] && DRM [=m] && MMU [=y]
> >   - DRM_ANALOGIX_ANX78XX [=m] && HAS_IOMEM [=y] && DRM [=m] && DRM_BRIDGE [=y]
>
> Please read Documentation/kbuild/kconfig-language.rst.
>
> Basically boolean DRM_PANEL_BRIDGE selecting tristate DRM_KMS_HELPER
> forces it to y while it should remain m.

Would you know the correct fix for this? I'm aware of the pattern
"select FOO || !FOO" but I guess it's also not applicable here?

In any case building DRM_PANEL_BRIDGE also needs to build
DRM_KMS_HELPER, otherwise the object files just don't get used.

Unfortunately I'm not versed well enough at all in Kconfig :/

>
> Please revert.
>
> BR,
> Jani.