Re: [PATCH 1/2] drm: fix drm_vm for NOMMU builds

[Arnd Bergmann <arnd@arndb.de>]

On Wednesday, January 11, 2017 5:27:13 PM CET Daniel Vetter wrote:
> On Wed, Jan 11, 2017 at 02:33:34PM +0100, Arnd Bergmann wrote:
> > When building DRM without an MMU, we run into a compile-time error because
> > pte_wrprotect() is not defined:
> > 
> > drivers/gpu/drm/drm_vm.c: In function 'drm_mmap_dma':
> > drivers/gpu/drm/drm_vm.c:496:9: error: implicit declaration of function 'pte_wrprotect' [-Werror=implicit-function-declaration]
> > 
> > The line is not meaningful here, so we can simply add another
> > compile-time check around it.
> > 
> > Fixes: 62a0d98a188c ("drm: allow to use mmuless SoC")
> > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> 
> We don't need drm_vm.c on modern drivers, and the idea was to simply not
> compile it when not needed. See:
> 
> commit 99c48e1e38f0aeaa107ad67c8d91f6c9d9d567a9
> Author: Benjamin Gaignard <benjamin.gaignard@linaro.org>
> Date:   Wed Jan 4 10:12:56 2017 +0100
> 
>     drm: compile drm_vm.c only when needed
> 
> 
> How did you manage to enable this stuff?
> -Daniel

This was a randconfig build, the DRM specific symbols here are

CONFIG_DRM=y
CONFIG_DRM_MIPI_DSI=y
# CONFIG_DRM_DP_AUX_CHARDEV is not set
# CONFIG_DRM_DEBUG_MM is not set
# CONFIG_DRM_DEBUG_MM_SELFTEST is not set
CONFIG_DRM_KMS_HELPER=y
CONFIG_DRM_KMS_FB_HELPER=y
# CONFIG_DRM_FBDEV_EMULATION is not set
CONFIG_DRM_LOAD_EDID_FIRMWARE=y
CONFIG_DRM_GEM_CMA_HELPER=y
CONFIG_DRM_KMS_CMA_HELPER=y
CONFIG_DRM_VM=y

#
# I2C encoder or helper chips
#
# CONFIG_DRM_I2C_CH7006 is not set
CONFIG_DRM_I2C_SIL164=y
# CONFIG_DRM_I2C_NXP_TDA998X is not set
CONFIG_DRM_ARM=y
CONFIG_DRM_HDLCD=y
CONFIG_DRM_HDLCD_SHOW_UNDERRUN=y
# CONFIG_DRM_MALI_DISPLAY is not set

#
# ACP (Audio CoProcessor) Configuration
#
CONFIG_DRM_VGEM=y
CONFIG_DRM_ROCKCHIP=y
CONFIG_ROCKCHIP_ANALOGIX_DP=y
CONFIG_ROCKCHIP_DW_HDMI=m
CONFIG_ROCKCHIP_DW_MIPI_DSI=y
CONFIG_ROCKCHIP_INNO_HDMI=m
# CONFIG_DRM_UDL is not set
CONFIG_DRM_ARMADA=y
CONFIG_DRM_ATMEL_HLCDC=m
CONFIG_DRM_RCAR_DU=y
# CONFIG_DRM_RCAR_HDMI is not set
CONFIG_DRM_RCAR_LVDS=y
# CONFIG_DRM_SHMOBILE is not set
CONFIG_DRM_SUN4I=y
CONFIG_DRM_TILCDC=m
CONFIG_DRM_TILCDC_SLAVE_COMPAT=y
CONFIG_DRM_MSM=y
CONFIG_DRM_MSM_REGISTER_LOGGING=y
CONFIG_DRM_MSM_HDMI_HDCP=y
CONFIG_DRM_MSM_DSI=y
# CONFIG_DRM_MSM_DSI_PLL is not set
# CONFIG_DRM_MSM_DSI_28NM_PHY is not set
# CONFIG_DRM_MSM_DSI_20NM_PHY is not set
CONFIG_DRM_MSM_DSI_28NM_8960_PHY=y
# CONFIG_DRM_FSL_DCU is not set
# CONFIG_DRM_TEGRA is not set
CONFIG_DRM_PANEL=y

#
# Display Panels
#
CONFIG_DRM_PANEL_SIMPLE=m
CONFIG_DRM_PANEL_JDI_LT070ME05000=m
CONFIG_DRM_PANEL_PANASONIC_VVX10F034N00=m
# CONFIG_DRM_PANEL_SAMSUNG_S6E8AA0 is not set
# CONFIG_DRM_PANEL_SHARP_LQ101R1SX01 is not set
# CONFIG_DRM_PANEL_SHARP_LS043T1LE01 is not set
CONFIG_DRM_BRIDGE=y

#
# Display Interface Bridges
#
CONFIG_DRM_ANALOGIX_ANX78XX=y
CONFIG_DRM_DUMB_VGA_DAC=m
CONFIG_DRM_DW_HDMI=m
CONFIG_DRM_DW_HDMI_AHB_AUDIO=m
# CONFIG_DRM_NXP_PTN3460 is not set
CONFIG_DRM_PARADE_PS8622=m
# CONFIG_DRM_SIL_SII8620 is not set
# CONFIG_DRM_SII902X is not set
# CONFIG_DRM_TOSHIBA_TC358767 is not set
CONFIG_DRM_TI_TFP410=y
CONFIG_DRM_ANALOGIX_DP=y
# CONFIG_DRM_I2C_ADV7511 is not set
CONFIG_DRM_VC4=m
CONFIG_DRM_ETNAVIV=m
# CONFIG_DRM_ETNAVIV_REGISTER_LOGGING is not set
CONFIG_DRM_ARCPGU=m
CONFIG_DRM_MXS=y
CONFIG_DRM_MXSFB=m
CONFIG_DRM_MESON=y
CONFIG_DRM_LEGACY=y
# CONFIG_DRM_LIB_RANDOM is not set

No idea what did it in the end.

I also have some older build fixes applied, so it may be something that
happens on my tree but not on plain linux-next.

	Arnd