mtk camera kernel makefile

对makefile一知半解，就通过camera kernel大概学习下，至少能读懂大部分意思

1.Kconfig

kernel-4.19/drivers/misc/mediatek/imgsensor/Kconfig
参考：https://blog.csdn.net/u011425939/article/details/80472324

config MTK_IMGSENSORbool "Camera Imgsensor Driver Support"helpKernel space image sensor driver. Define  project used all imagesensors .The value is combination of CUSTOM_KERNEL_MAIN_IMGSENSOR,CUSTOM_KERNEL_MAIN_BACKUP_IMGSENSOR, CUSTOM_KERNEL_SUB_IMGSENSOR,and CUSTOM_KERNEL_SUB_BACKUP_IMGSENSORsource "drivers/misc/mediatek/imgsensor/src/Kconfig"

主要就是bool类型的Camera Imgsensor Driver Support，用来配置内核
source条目用于读取另一个Kconfig文件
继续看src下的Kconfig

config SPECIFY_IMGSENSORbool SPECIFY_IMGSENSORdepends on MTK_IMGSENSORhelpSpecify name of each sensor toprevent obtaining wrong sensor driver with same sensor ID.For example, imx258_mipi_raw and imx258_mipi_monoare of same sensor ID. If not specifyingsensor, imx258_mipi_mono may be recognized as imx258_mipi_raw.config IMGSENSOR_MAINstring "Custom main image sensor"depends on SPECIFY_IMGSENSORhelpSpecify main sensor.This config is mainly mapping to userspace.Consider the numbers of sensors and usage on the phone.Compare the custom usage defined in user-custom folder.config IMGSENSOR_MAIN2string "Custom main2 image sensor"depends on SPECIFY_IMGSENSORhelpSpecify main2 sensor.This config is mainly mapping to userspace.Consider the numbers of sensors and usage on the phone.Compare the custom usage defined in user-custom folder.

SPECIFY_IMGSENSOR依赖与上层的MTK_IMGSENSOR，而IMGSENSOR_MAIN等依赖SPECIFY_IMGSENSOR

2.Makefile

kernel-4.19/drivers/misc/mediatek/imgsensor/src/Makefile

subdir-ccflags-y += -I$(srctree)/drivers/i2c/busses/ \-I$(srctree)/drivers/misc/mediatek/mmdvfs/ \-I$(srctree)/drivers/misc/mediatek/ccu/inc
#kbuild就会将以上三个目录添加到编译时的头文件搜索目录中，对其subdir也有效。
MTK_PLATFORM := $(subst ",,$(CONFIG_MTK_PLATFORM))
ARCH_MTK_PROJECT := $(subst ",,$(CONFIG_ARCH_MTK_PROJECT))
#将“替换成无，或者理解为去掉"
MTK_PLATFORM_PATH_ROOT := $(srctree)/drivers/misc/mediatek/mach/$(MTK_PLATFORM)
MTK_PROJECT_PATH_ROOT := $(srctree)/drivers/misc/mediatek/mach/$(MTK_PLATFORM)/$(ARCH_MTK_PROJECT)CONFIG_MTK_PLATFORM_SENSOR := $(CONFIG_MTK_PLATFORM)subdir-ccflags-y += -I$(MTK_PROJECT_PATH_ROOT)/camera/cameraMTK_DRIVER_PATH  := $(srctree)/drivers/misc/mediateksubdir-ccflags-y += -I$(MTK_DRIVER_PATH)/camera/$(MTK_PLATFORM) \-I$(MTK_DRIVER_PATH)/imgsensor/inc \-I$(MTK_DRIVER_PATH)/imgsensor/src/$(CONFIG_MTK_PLATFORM_SENSOR)/camera_project/$(ARCH_MTK_PROJECT)/camera_hw \-I$(MTK_DRIVER_PATH)/imgsensor/src/$(CONFIG_MTK_PLATFORM_SENSOR)/camera_hw \-I$(MTK_DRIVER_PATH)/cam_cal/inc \-I$(MTK_DRIVER_PATH)/smi \-I$(MTK_DRIVER_PATH)/include/mt-plat/$(MTK_PLATFORM)/include/mach \-I$(MTK_DRIVER_PATH)/imgsensor/src/$(CONFIG_MTK_PLATFORM_SENSOR)subdir-ccflags-$(CONFIG_TINNO_PRODUCT_INFO) += -I$(srctree)/drivers/misc/dev_infoCUSTOM_KERNEL_FLAGS := $(addprefix -D, $(shell echo \$(CONFIG_CUSTOM_KERNEL_IMGSENSOR) | tr a-z A-Z))
#添加添加-D前缀，小写转大写   -D为添加宏定义
subdir-ccflags-y += $(CUSTOM_KERNEL_FLAGS)obj-y += $(subst ",,$(CONFIG_MTK_PLATFORM_SENSOR))/

再继续看下层makefile,如MTK_PLATFORM所对应的mt6765

MTK_PLATFORM := $(subst ",,$(CONFIG_MTK_PLATFORM))
ARCH_MTK_PROJECT := $(subst ",,$(CONFIG_ARCH_MTK_PROJECT))
IMGSENSOR_DRIVER_PATH  := $(srctree)/drivers/misc/mediatek/imgsensor/src
COMMON_VERSION := v1subdir-ccflags-y +=  -I$(IMGSENSOR_DRIVER_PATH)/common/$(COMMON_VERSION)
obj-y               += ../common/$(COMMON_VERSION)/imgsensor.o
obj-y               += ../common/$(COMMON_VERSION)/imgsensor.o
obj-y               += ../common/$(COMMON_VERSION)/imgsensor_hw.o
obj-y               += ../common/$(COMMON_VERSION)/imgsensor_i2c.o
obj-y               += ../common/$(COMMON_VERSION)/imgsensor_legacy.o
obj-y               += ../common/$(COMMON_VERSION)/imgsensor_proc.o
ifeq (,$(wildcard $(IMGSENSOR_DRIVER_PATH)/$(MTK_PLATFORM)/camera_project/$(ARCH_MTK_PROJECT)/$(COMMON_VERSION)))
#wildcard展开为已经存在的、使用空格分开的、匹配此模式的所有文件列表。如果不存在任何符合此模式的文件，函数会忽略模式字符并返回空
obj-y               += ../common/$(COMMON_VERSION)/imgsensor_sensor_list.o
else
obj-y               += camera_project/$(ARCH_MTK_PROJECT)/$(COMMON_VERSION)/imgsensor_sensor_list.o
endif
#此处可理解为匹配imgsensor_sensor_list.c文件，camera_project/$(ARCH_MTK_PROJECT)/$(COMMON_VERSION)/imgsensor_sensor_list.o优先级高于common目录下的

这里 $ (1)可理解为具体的每个camera驱动目录名称
两层判断，第一层：
如果在$ (IMGSENSOR_DRIVER_PATH)/ $ (MTK_PLATFORM)/camera_project/ $ (ARCH_MTK_PROJECT)/ $ (COMMON_VERSION)/ $ (1)如果没找到，进入第二层循环，找到了，就将platform_drv赋值。
第二层：
继续在 $ (IMGSENSOR_DRIVER_PATH)/ $ (MTK_PLATFORM)/下找，没找到，就最后在common/$(COMMON_VERSION)/下找

综上：查找具体sensor驱动目录优先级为
1.mediatek/imgsensor/src/mt6765/camera_project/$(ARCH_MTK_PROJECT)/v1
2.mediatek/imgsensor/src/mt6765
3.mediatek/imgsensor/src/common/v1

继续看剩下部分：

ifneq ($(common_drv),)
$(info imgsensor drv by common $(common_drv))
endif
obj-y               += $(common_drv)ifneq ($(platform_drv),)
$(info imgsensor drv by platform $(platform_drv))
#此处会打印出匹配出的驱动目录
endif
obj-y               += $(platform_drv)
obj-y               += imgsensor_clk.oifneq ($(project_drv),)
$(info imgsensor drv by platform $(project_drv))
endif
obj-y               += $(project_drv)ifeq (,$(wildcard $(IMGSENSOR_DRIVER_PATH)/$(MTK_PLATFORM)/camera_project/$(ARCH_MTK_PROJECT)/camera_hw))
subdir-ccflags-y        += -I$(IMGSENSOR_DRIVER_PATH)/$(MTK_PLATFORM)/camera_hw
obj-y               += camera_hw/
ifneq ($(project_drv),)
obj-y               += camera_project/$(ARCH_MTK_PROJECT)/
endif
else
obj-y               += camera_project/$(ARCH_MTK_PROJECT)/camera_hw/
subdir-ccflags-y        += -I$(IMGSENSOR_DRIVER_PATH)/$(MTK_PLATFORM)/camera_project/$(ARCH_MTK_PROJECT)/camera_hw
endif
#选择camera_hw/，原理同上