linux-kernel - Re: [PATCH 5.15 808/917] drm: fb_helper: improve CONFIG

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Date:   Fri, 19 Nov 2021 09:10:30 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Jiri Slaby <jirislaby@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "# 3.4.x" <stable@...r.kernel.org>,
        "Acked-by: Jani Nikula" <jani.nikula@...el.com>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.15 808/917] drm: fb_helper: improve CONFIG_FB dependency

On Fri, Nov 19, 2021 at 8:56 AM Jiri Slaby <jirislaby@...nel.org> wrote:
>
> On 19. 11. 21, 8:50, Jiri Slaby wrote:
> > On 15. 11. 21, 18:05, Greg Kroah-Hartman wrote:
> >> From: Arnd Bergmann <arnd@...db.de>
> >>
> >> [ Upstream commit 9d6366e743f37d36ef69347924ead7bcc596076e ]
> >
> > Hi,
> >
> > this breaks build on openSUSE's armv7hl config:
> > $ wget -O .config
> > https://raw.githubusercontent.com/openSUSE/kernel-source/stable/config/armv7hl/default
> >
> > $ make -j168 CROSS_COMPILE=arm-suse-linux-gnueabi- ARCH=arm vmlinux
> > ...
> >    LD      .tmp_vmlinux.btf
> > arm-suse-linux-gnueabi-ld: drivers/gpu/drm/panel/panel-simple.o: in
> > function `panel_simple_probe':
> > drivers/gpu/drm/panel/panel-simple.c:803: undefined reference to
> > `drm_panel_dp_aux_backlight'
> > $ grep -E 'CONFIG_(DRM|FB|DRM_KMS_HELPER|DRM_FBDEV_EMULATION)\>' .config
> > CONFIG_DRM=y
> > CONFIG_DRM_KMS_HELPER=m
> > CONFIG_DRM_FBDEV_EMULATION=y
> > CONFIG_FB=y
> >
> > 5.16-rc1 builds just fine -- investigating why…
>
> CLearly because the code moved to panel-edp.c. So doing:
> -CONFIG_DRM_PANEL_EDP=m
> +CONFIG_DRM_PANEL_EDP=y
> leads to the same error in that file:
> arm-suse-linux-gnueabi-ld: drivers/gpu/drm/panel/panel-edp.o: in
> function `panel_edp_probe':
> drivers/gpu/drm/panel/panel-edp.c:843: undefined reference to
> `drm_panel_dp_aux_backlight'

Ah right, I ran into a similar thing on my randconfig builds, this is
what I have
applied locally but wasn't completely sure about yet, it may need additional
'select DRM_KMS_CMA_HELPER' to cover all instances:

commit 8dd05af5243f3ab968b317ef82b3c0d04079b805
Author: Arnd Bergmann <arnd@...db.de>
Date:   Mon Nov 15 16:54:04 2021 +0100

    drm/mipi-dbi: select CONFIG_DRM_KMS_HELPER

    The driver fails to build when the KMS helpers are disabled:

    ld.lld: error: undefined symbol: drm_gem_fb_get_obj
    >>> referenced by drm_mipi_dbi.c
    >>>               gpu/drm/drm_mipi_dbi.o:(mipi_dbi_buf_copy) in
archive drivers/built-in.a
    >>> referenced by drm_mipi_dbi.c
    >>>               gpu/drm/drm_mipi_dbi.o:(mipi_dbi_fb_dirty) in
archive drivers/built-in.a

    ld.lld: error: undefined symbol: drm_gem_fb_begin_cpu_access
    >>> referenced by drm_mipi_dbi.c
    >>>               gpu/drm/drm_mipi_dbi.o:(mipi_dbi_buf_copy) in
archive drivers/built-in.a

    ld.lld: error: undefined symbol: drm_fb_swab
    >>> referenced by drm_mipi_dbi.c
    >>>               gpu/drm/drm_mipi_dbi.o:(mipi_dbi_buf_copy) in
archive drivers/built-in.a

    ld.lld: error: undefined symbol: drm_fb_xrgb8888_to_rgb565
    >>> referenced by drm_mipi_dbi.c
    >>>               gpu/drm/drm_mipi_dbi.o:(mipi_dbi_buf_copy) in
archive drivers/built-in.a

    ld.lld: error: undefined symbol: drm_fb_memcpy
    >>> referenced by drm_mipi_dbi.c
    >>>               gpu/drm/drm_mipi_dbi.o:(mipi_dbi_buf_copy) in
archive drivers/built-in.a

    This is fairly hard to hit in randconfig drivers, but it eventually
    did trigger for me in a configuration where all other DRM drivers
    are loadable modules, but DRM_PANEL_WIDECHIPS_WS2401 was built-in.

    Signed-off-by: Arnd Bergmann <arnd@...db.de>

diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 0039df26854b..a03c2761c5f9 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -29,6 +29,7 @@ menuconfig DRM

 config DRM_MIPI_DBI
        tristate
+       select DRM_KMS_HELPER
        depends on DRM

 config DRM_MIPI_DSI
diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index 431b6e12a81f..17a8d603e7d8 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -8,7 +8,6 @@ config DRM_BRIDGE
 config DRM_PANEL_BRIDGE
        def_bool y
        depends on DRM_BRIDGE
-       depends on DRM_KMS_HELPER
        select DRM_PANEL
        help
          DRM bridge wrapper of DRM panels
diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
index cfc8d644cedf..40ec20f3552d 100644
--- a/drivers/gpu/drm/panel/Kconfig
+++ b/drivers/gpu/drm/panel/Kconfig
@@ -140,9 +140,8 @@ config DRM_PANEL_ILITEK_IL9322
 config DRM_PANEL_ILITEK_ILI9341
        tristate "Ilitek ILI9341 240x320 QVGA panels"
        depends on OF && SPI
-       depends on DRM_KMS_HELPER
-       depends on DRM_KMS_CMA_HELPER
        depends on BACKLIGHT_CLASS_DEVICE
+       select DRM_KMS_CMA_HELPER
        select DRM_MIPI_DBI
        help
          Say Y here if you want to enable support for Ilitek IL9341