linux-kernel - [PATCH 1/2] fbdev: don't select I2C directly

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Date:   Mon, 15 Jan 2018 17:14:04 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Rob Clark <robdclark@...il.com>
Cc:     Jordan Crouse <jcrouse@...eaurora.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        linux-i2c@...r.kernel.org, Wolfram Sang <wsa@...-dreams.de>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] fbdev: don't select I2C directly

Using a Kconfig 'select' statement for a user-visible symbol that other
drivers depend on often causes circular dependencies. A new one showed
up when I wanted to add an NVMEM dependency to the DRM_MSM driver:

drivers/i2c/Kconfig:7:error: recursive dependency detected!
drivers/i2c/Kconfig:7:	symbol I2C is selected by FB_DDC
drivers/video/fbdev/Kconfig:63:	symbol FB_DDC is selected by FB_CYBER2000_DDC
drivers/video/fbdev/Kconfig:390:	symbol FB_CYBER2000_DDC depends on FB_CYBER2000
drivers/video/fbdev/Kconfig:378:	symbol FB_CYBER2000 depends on FB
drivers/video/fbdev/Kconfig:5:	symbol FB is selected by DRM_KMS_FB_HELPER
drivers/gpu/drm/Kconfig:77:	symbol DRM_KMS_FB_HELPER depends on DRM_KMS_HELPER
drivers/gpu/drm/Kconfig:71:	symbol DRM_KMS_HELPER is selected by DRM_MSM
drivers/gpu/drm/msm/Kconfig:2:	symbol DRM_MSM depends on NVMEM
drivers/nvmem/Kconfig:1:	symbol NVMEM is selected by EEPROM_AT24
drivers/misc/eeprom/Kconfig:3:	symbol EEPROM_AT24 depends on I2C

Here, the problem is that many fbdev drivers have an i2c based interface
and just 'select i2c' for that, while we also select the framebuffer
subsystem indirectly from a DRM driver that now depends on i2c.

This does away with the 'select' statement and instead uses 'depends on',
like almost all I2C users.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/video/fbdev/Kconfig | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/video/fbdev/Kconfig b/drivers/video/fbdev/Kconfig
index 6962b4583fd7..892eb1863100 100644
--- a/drivers/video/fbdev/Kconfig
+++ b/drivers/video/fbdev/Kconfig
@@ -64,7 +64,6 @@ config FB_DDC
        tristate
        depends on FB
        select I2C_ALGOBIT
-       select I2C
        default n
 
 config FB_BOOT_VESA_SUPPORT
@@ -390,6 +389,7 @@ config FB_CYBER2000
 config FB_CYBER2000_DDC
 	bool "DDC for CyberPro support"
 	depends on FB_CYBER2000
+	depends on I2C=y || I2C=FB_CYBER2000
 	select FB_DDC
 	default y
 	help
@@ -634,7 +634,7 @@ config FB_BF537_LQ035
 config FB_BFIN_7393
 	tristate "Blackfin ADV7393 Video encoder"
 	depends on FB && BLACKFIN
-	select I2C
+	depends on I2C
 	select FB_CFB_FILLRECT
 	select FB_CFB_COPYAREA
 	select FB_CFB_IMAGEBLIT
@@ -1026,6 +1026,7 @@ config FB_NVIDIA
 config FB_NVIDIA_I2C
        bool "Enable DDC Support"
        depends on FB_NVIDIA
+       depends on I2C=y || I2C=FB_NVIDIA
        select FB_DDC
        help
 	  This enables I2C support for nVidia Chipsets.  This is used
@@ -1073,6 +1074,7 @@ config FB_RIVA
 config FB_RIVA_I2C
        bool "Enable DDC Support"
        depends on FB_RIVA
+       depends on I2C=y || I2C=FB_RIVA
        select FB_DDC
        help
 	  This enables I2C support for nVidia Chipsets.  This is used
@@ -1102,6 +1104,7 @@ config FB_RIVA_BACKLIGHT
 config FB_I740
 	tristate "Intel740 support"
 	depends on FB && PCI
+	depends on I2C
 	select FB_MODE_HELPERS
 	select FB_CFB_FILLRECT
 	select FB_CFB_COPYAREA
@@ -1155,6 +1158,7 @@ config FB_I810_GTF
 config FB_I810_I2C
 	bool "Enable DDC Support"
 	depends on FB_I810 && FB_I810_GTF
+	depends on I2C=y || I2C=FB_I810
 	select FB_DDC
 	help
 
@@ -1206,6 +1210,7 @@ config FB_INTEL_DEBUG
 config FB_INTEL_I2C
 	bool "DDC/I2C for Intel framebuffer support"
 	depends on FB_INTEL
+	depends on I2C=y || I2C=FB_INTEL
 	select FB_DDC
 	default y
 	help
@@ -1285,6 +1290,7 @@ config FB_MATROX_G
 config FB_MATROX_I2C
 	tristate "Matrox I2C support"
 	depends on FB_MATROX
+	depends on I2C
 	select FB_DDC
 	---help---
 	  This drivers creates I2C buses which are needed for accessing the
@@ -1350,6 +1356,7 @@ config FB_RADEON
 config FB_RADEON_I2C
 	bool "DDC/I2C for ATI Radeon support"
 	depends on FB_RADEON
+	depends on I2C=y || I2C=FB_RADEON
 	select FB_DDC
 	default y
 	help
@@ -1460,6 +1467,7 @@ config FB_S3
 config FB_S3_DDC
 	bool "DDC for S3 support"
 	depends on FB_S3
+	depends on I2C=y || I2C=FB_S3
 	select FB_DDC
 	default y
 	help
@@ -1485,6 +1493,7 @@ config FB_SAVAGE
 config FB_SAVAGE_I2C
        bool "Enable DDC2 Support"
        depends on FB_SAVAGE
+       depends on I2C=y || I2C=FB_SAVAGE
        select FB_DDC
        help
 	  This enables I2C support for S3 Savage Chipsets.  This is used
@@ -1629,6 +1638,7 @@ config FB_3DFX_ACCEL
 config FB_3DFX_I2C
 	bool "Enable DDC/I2C support"
 	depends on FB_3DFX
+	depends on I2C=y || I2C=FB_3DFX
 	select FB_DDC
 	default y
 	help
@@ -1669,6 +1679,7 @@ config FB_VT8623
 config FB_TRIDENT
 	tristate "Trident/CyberXXX/CyberBlade support"
 	depends on FB && PCI
+	depends on I2C
 	select FB_CFB_FILLRECT
 	select FB_CFB_COPYAREA
 	select FB_CFB_IMAGEBLIT
@@ -2299,8 +2310,8 @@ endchoice
 
 config FB_MB862XX_I2C
 	bool "Support I2C bus on MB862XX GDC"
-	depends on FB_MB862XX && I2C
-	depends on FB_MB862XX=m || I2C=y
+	depends on FB_MB862XX
+	depends on I2C=y || I2C=FB_MB862XX
 	default y
 	help
 	  Selecting this option adds Coral-P(A)/Lime GDC I2C bus adapter
-- 
2.9.0