drivers: add support for forcing out-of-tree drivers

An external project extending the Zephyr RTOS and its drivers may have
subsystems that must use its own specific driver(s) when active. One
example is the nRF5x NVMC that must be scheduled in between radio
operations. A subsystem may also be dependent on its own drivers for
security, real-time and/or because of hardware constrains.

In order to not introduce non-Zephyr specific code into the Zephyr tree,
an option is added to disable the in-tree drivers in Zephyr. Because
Kconfig does not support a good way of de-selecting other symbols, a
variable on the form `<DRIVER>_MUST_USE_OUT_OF_TREE_DRIVER` is added as
a dependency for each `<DRIVER>`. For example, the out-of-tree subsystem
will select `FLASH_MUST_USE_OUT_OF_TREE_DRIVER` to disable all in-tree
drivers. A solution for issue #8181 would open up for a more general
solution, however #8181 requires significant effort.

Support for out-of-tree drivers is added to clock_control, entropy and
flash.

Signed-off-by: Thomas Stenersen <[email protected]>

Author: Thomas Stenersen

drivers/clock_control/Kconfig

@@ -9,6 +9,13 @@
 #
 # Clock controller drivers
 #
+
+config CLOCK_CONTROL_MUST_USE_OUT_OF_TREE_DRIVER
+	bool
+	help
+	  This option can be enabled by an out-of-tree library if it
+	  needs to take control over the clock controller.
+
 menuconfig CLOCK_CONTROL
 	bool "Hardware clock controller support"
 	help
@@ -23,18 +30,15 @@ module = CLOCK_CONTROL
 module-str = clock control
 source "subsys/logging/Kconfig.template.log_config"
 
-source "drivers/clock_control/Kconfig.nrf"
 
+if !CLOCK_CONTROL_MUST_USE_OUT_OF_TREE_DRIVER
+source "drivers/clock_control/Kconfig.nrf"
 source "drivers/clock_control/Kconfig.quark_se"
-
 source "drivers/clock_control/Kconfig.stm32"
-
 source "drivers/clock_control/Kconfig.beetle"
-
 source "drivers/clock_control/Kconfig.mcux_ccm"
-
 source "drivers/clock_control/Kconfig.mcux_sim"
-
 source "drivers/clock_control/Kconfig.rv32m1"
+endif # !CLOCK_CONTROL_MUST_USE_OUT_OF_TREE_DRIVER
 
 endif # CLOCK_CONTROL

drivers/entropy/Kconfig

@@ -6,19 +6,28 @@
 # SPDX-License-Identifier: Apache-2.0
 #
 
+config ENTROPY_MUST_USE_OUT_OF_TREE_DRIVER
+	bool
+	help
+	  This option can be enabled by an out-of-tree library if it
+	  needs to take control over the entropy driver.
+
 menuconfig ENTROPY_GENERATOR
 	bool "Entropy Drivers"
 	help
 	  Include entropy drivers in system config.
 
+
 if ENTROPY_GENERATOR
 
+if !ENTROPY_MUST_USE_OUT_OF_TREE_DRIVER
 source "drivers/entropy/Kconfig.mcux"
 source "drivers/entropy/Kconfig.stm32"
 source "drivers/entropy/Kconfig.esp32"
 source "drivers/entropy/Kconfig.nrf5"
 source "drivers/entropy/Kconfig.sam"
 source "drivers/entropy/Kconfig.native_posix"
+endif # !ENTROPY_MUST_USE_OUT_OF_TREE_DRIVER
 
 config ENTROPY_HAS_DRIVER
 	bool

drivers/flash/Kconfig

@@ -20,6 +20,12 @@ config FLASH_HAS_PAGE_LAYOUT
 	  This option is enabled when the SoC flash driver supports
 	  retrieving the layout of flash memory pages.
 
+config FLASH_MUST_USE_OUT_OF_TREE_DRIVER
+	bool
+	help
+	  This option can be enabled by an out-of-tree library if it
+	  needs to take control over the flash memory peripheral.
+
 menuconfig FLASH
 	bool "Flash hardware support"
 	help
@@ -45,24 +51,17 @@ config FLASH_PAGE_LAYOUT
 	help
 	  Enables API for retrieving the layout of flash memory pages.
 
+if !FLASH_MUST_USE_OUT_OF_TREE_DRIVER
 source "drivers/flash/Kconfig.nrf"
-
 source "drivers/flash/Kconfig.mcux"
-
 source "drivers/flash/Kconfig.nios2_qspi"
-
 source "drivers/flash/Kconfig.gecko"
-
 source "drivers/flash/Kconfig.nor"
-
 source "drivers/flash/Kconfig.qmsi"
-
 source "drivers/flash/Kconfig.stm32"
-
 source "drivers/flash/Kconfig.sam0"
-
 source "drivers/flash/Kconfig.sam"
-
 source "drivers/flash/Kconfig.w25qxxdv"
+endif # !FLASH_MUST_USE_OUT_OF_TREE_DRIVER
 
 endif # FLASH