Re: [PATCH] drm/panel: add CONFIG_DRM_KMS_HELPER dependencies

[Thomas Zimmermann <tzimmermann@xxxxxxx>]

Am 16.03.22 um 20:12 schrieb Thomas Zimmermann:
> Hi
>
> Am 16.03.22 um 19:36 schrieb Arnd Bergmann:
> > From: Arnd Bergmann <arnd@xxxxxxxx>
> >
> > 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.
> >
> > Adding a dependency in all drivers that select DRM_MIPI_DBI avoids
> > the problem for now, adding the dependency in DRM_MIPI_DBI as well
> > should help make it easier to figure out why it breaks if someone
> > forgets the dependency the next time.
> >
> > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> > ---
> >   drivers/gpu/drm/Kconfig       | 2 +-
> >   drivers/gpu/drm/panel/Kconfig | 4 ++++
> >   2 files changed, 5 insertions(+), 1 deletion(-)
> >
> > I see this warning on 5.17-rc8, but did not test it on linux-next,
> > which may already have a fix.
> >
> >
> > diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> > index b1f22e457fd0..d5ec0b77c010 100644
> > --- a/drivers/gpu/drm/Kconfig
> > +++ b/drivers/gpu/drm/Kconfig
> > @@ -30,7 +30,7 @@ menuconfig DRM
> >   config DRM_MIPI_DBI
> >       tristate
> > -    depends on DRM
> > +    depends on DRM_KMS_HELPER
>
> This symbol cannot be selected by users, so it's maybe not a good idea 
> to depend on it. In fact, I've had to remove such a statement because it 
> created a cyclic dependency. [1]

[1] 
https://lore.kernel.org/dri-devel/20220315084559.23510-1-tzimmermann@xxxxxxx/

> Making the drivers depend on KMS helpers is the right thing though. If 
> there's a better solution, please let me know.
>
> Best regards
> Thomas
>
> >   config DRM_MIPI_DSI
> >       bool
> > diff --git a/drivers/gpu/drm/panel/Kconfig 
> > b/drivers/gpu/drm/panel/Kconfig
> > index 0aec5a10b064..96887d0efb9f 100644
> > --- a/drivers/gpu/drm/panel/Kconfig
> > +++ b/drivers/gpu/drm/panel/Kconfig
> > @@ -425,6 +425,7 @@ config DRM_PANEL_SAMSUNG_DB7430
> >       tristate "Samsung DB7430-based DPI panels"
> >       depends on OF && SPI && GPIOLIB
> >       depends on BACKLIGHT_CLASS_DEVICE
> > +    depends on DRM_KMS_HELPER
> >       select DRM_MIPI_DBI
> >       help
> >         Say Y here if you want to enable support for the Samsung
> > @@ -440,6 +441,7 @@ config DRM_PANEL_SAMSUNG_S6D16D0
> >   config DRM_PANEL_SAMSUNG_S6D27A1
> >       tristate "Samsung S6D27A1 DPI panel driver"
> >       depends on OF && SPI && GPIOLIB
> > +    depends on DRM_KMS_HELPER
> >       select DRM_MIPI_DBI
> >       help
> >         Say Y here if you want to enable support for the Samsung
> > @@ -476,6 +478,7 @@ config DRM_PANEL_SAMSUNG_S6E63M0_SPI
> >       depends on SPI
> >       depends on DRM_PANEL_SAMSUNG_S6E63M0
> >       default DRM_PANEL_SAMSUNG_S6E63M0
> > +    depends on DRM_KMS_HELPER
> >       select DRM_MIPI_DBI
> >       help
> >         Say Y here if you want to be able to access the Samsung
> > @@ -677,6 +680,7 @@ config DRM_PANEL_WIDECHIPS_WS2401
> >       tristate "Widechips WS2401 DPI panel driver"
> >       depends on SPI && GPIOLIB
> >       depends on BACKLIGHT_CLASS_DEVICE
> > +    depends on DRM_KMS_HELPER
> >       select DRM_MIPI_DBI
> >       help
> >         Say Y here if you want to enable support for the Widechips 
> > WS2401 DPI

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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