openwrt 编译内核模块中的配置问题

以 other.mk 中的iio 为例 对 KCONFIG下面的

define KernelPackage/iio-core
  SUBMENU:=$(OTHER_MENU)
  TITLE:=Industrial IO core
  KCONFIG:= \
    CONFIG_IIO \
    CONFIG_IIO_BUFFER=y \
    CONFIG_IIO_KFIFO_BUF \
    CONFIG_IIO_TRIGGER=y \
    CONFIG_IIO_TRIGGERED_BUFFER
  FILES:= \
    $(LINUX_DIR)/drivers/iio/industrialio.ko \
    $(if $(CONFIG_IIO_TRIGGERED_BUFFER),$(LINUX_DIR)/drivers/iio/industrialio-triggered-buffer.ko) \
    $(LINUX_DIR)/drivers/iio/kfifo_buf.ko
  AUTOLOAD:=$(call AutoLoad,55,industrialio kfifo_buf industrialio-triggered-buffer)
endef

define KernelPackage/iio-core/description
 The industrial I/O subsystem provides a unified framework for
 drivers for many different types of embedded sensors using a
 number of different physical interfaces (i2c, spi, etc)
endef

$(eval $(call KernelPackage,iio-core))

iio 跟目录下Makefile部分内容

通过make menuconfig 选中 GONFIG_IIO后，编译后，编译的内容

GONFIG_IIO ：编译了 industrialio-core.c inkern.c industrialio-event.c
CONFIG_IIO_BUFFER=y ： 编译了 industrialio-buffer.c
CONFIG_IIO_TRIGGER=y ： 编译了 industrialio-trigger.c
上述五个文件共同编译了组件： industrialio.ko

$(LINUX_DIR)/drivers/iio/kfifo_buf.ko // 这句话使得 kfifo_buf.ko 模块编译，
                                    //但是CONFIG_IIO_KFIFO_BUF 没有选中
                                    //说明，CONFIG_IIO_KFIFO_BUF=y对模块是否编译无影响   

改变KCONFIG, 后再编译

 KCONFIG:= \
    CONFIG_IIO \
    CONFIG_IIO_BUFFER=y \
    CONFIG_IIO_KFIFO_BUF \
    CONFIG_IIO_BUFFER_CB=y \
    CONFIG_IIO_TRIGGER \
    CONFIG_IIO_TRIGGERED_BUFFER=y \

并没有出现 industrialio-triggered-buffer.ko 模块
同时 industrialio-buffer.c 也编译了
与预期的不同，所需要看Kconfig文件中的依赖关系

#
# Industrial I/O subsystem configuration
#

menuconfig IIO
    tristate "Industrial I/O support"
    select ANON_INODES
    help
      The industrial I/O subsystem provides a unified framework for
      drivers for many different types of embedded sensors using a
      number of different physical interfaces (i2c, spi, etc).

if IIO

config IIO_BUFFER
    bool "Enable buffer support within IIO"
    help
      Provide core support for various buffer based data
      acquisition methods.

if IIO_BUFFER

config IIO_BUFFER_CB
boolean "IIO callback buffer used for push in-kernel interfaces"
    help
      Should be selected by any drivers that do in-kernel push
      usage.  That is, those where the data is pushed to the consumer.

config IIO_KFIFO_BUF
    select IIO_TRIGGER
    tristate "Industrial I/O buffering based on kfifo"
    help
      A simple fifo based on kfifo.  Note that this currently provides
      no buffer events so it is up to userspace to work out how
      often to read from the buffer.

config IIO_TRIGGERED_BUFFER
    tristate
    select IIO_TRIGGER
    select IIO_KFIFO_BUF
    help
      Provides helper functions for setting up triggered buffers.

endif # IIO_BUFFER

config IIO_TRIGGER
    boolean "Enable triggered sampling support"
    help
      Provides IIO core support for triggers.  Currently these
      are used to initialize capture of samples to push into
      buffers.  The triggers are effectively a 'capture
      data now' interrupt.

config IIO_CONSUMERS_PER_TRIGGER
       int "Maximum number of consumers per trigger"
       depends on IIO_TRIGGER
       default "2"
       help
    This value controls the maximum number of consumers that a
    given trigger may handle. Default is 2.

更改KCONFIG，重新编译：

    CONFIG_IIO \
    CONFIG_IIO_BUFFER \
    CONFIG_IIO_KFIFO_BUF \
    CONFIG_IIO_TRIGGER \
    CONFIG_IIO_TRIGGERED_BUFFER

可以看到，kfifo_buf.ko 模块没有生成，是因为在Kconfig 文件中看出 IIO_TRIGGER的依赖关系

config IIO_KFIFO_BUF
    select IIO_TRIGGER
//而 IIO_TRIGGER

但是仅仅选中 设置 CONFIG_IIO_TRIGGER=y 编译也是通不过的，重新观察发现 只有预先选中IIO_BUFFER, 才能选中_IIO_TRIGGER

if IIO_BUFFER

config IIO_BUFFER_CB
boolean “IIO callback buffer used for push in-kernel interfaces”
help
Should be selected by any drivers that do in-kernel push
usage. That is, those where the data is pushed to the consumer.

config IIO_KFIFO_BUF
select IIO_TRIGGER
tristate “Industrial I/O buffering based on kfifo”
help
A simple fifo based on kfifo. Note that this currently provides
no buffer events so it is up to userspace to work out how
often to read from the buffer.

config IIO_TRIGGERED_BUFFER
tristate
select IIO_TRIGGER
select IIO_KFIFO_BUF
help
Provides helper functions for setting up triggered buffers.

endif # IIO_BUFFER

更改KCONFIG，重新编译：

    CONFIG_IIO \
    CONFIG_IIO_BUFFER=y \
    CONFIG_IIO_KFIFO_BUF \
    CONFIG_IIO_TRIGGER=y \
    CONFIG_IIO_TRIGGERED_BUFFER=y

并没有出现 industrialio-triggered-buffer.ko 模块

CONFIG_IIO_KFIFO_BUF=y 设置后，再编译还是没有出现 industrialio-triggered-buffer.ko 模块，原因待查
当选中
CONFIG_IIO_KFIFO_BUF=y 后，
$(LINUX_DIR)/drivers/iio/kfifo_buf.ko 就不需要了