#
# Makefile for the USB Mass Storage device drivers.
#
# 15 Aug 2000, Christoph Hellwig 
# Rewritten to use lists instead of if-statements.
#

EXTRA_CFLAGS := -Idrivers/scsi

obj-$(CONFIG_USB_STORAGE) += usb-storage.o

usb-storage-obj-$(CONFIG_USB_STORAGE_DEBUG) += debug.o
usb-storage-obj-$(CONFIG_USB_STORAGE_USBAT) += shuttle_usbat.o
usb-storage-obj-$(CONFIG_USB_STORAGE_SDDR09) += sddr09.o
usb-storage-obj-$(CONFIG_USB_STORAGE_SDDR55) += sddr55.o
usb-storage-obj-$(CONFIG_USB_STORAGE_FREECOM) += freecom.o
usb-storage-obj-$(CONFIG_USB_STORAGE_DPCM) += dpcm.o
usb-storage-obj-$(CONFIG_USB_STORAGE_ISD200) += isd200.o
usb-storage-obj-$(CONFIG_USB_STORAGE_DATAFAB) += datafab.o
usb-storage-obj-$(CONFIG_USB_STORAGE_JUMPSHOT) += jumpshot.o
usb-storage-obj-$(CONFIG_USB_STORAGE_ALAUDA) += alauda.o
usb-storage-obj-$(CONFIG_USB_STORAGE_ONETOUCH) += onetouch.o
usb-storage-obj-$(CONFIG_USB_STORAGE_KARMA) += karma.o

usb-storage-objs := scsiglue.o protocol.o transport.o usb.o 
initializers.o $(usb-storage-obj-y)

ifneq ($(CONFIG_USB_LIBUSUAL),)
obj-$(CONFIG_USB) += libusual.o
endif

###################################################################
EXTRA_CFLAGS := -Idrivers/scsi  这句目的是什么？-I好像是指定一个路径的把
这个Makefile的modulename.o应该是usb-storage.o吧，可是usb-storage-obj-*又是代表什么呢？
还有usb-storage-objs和usb-storage-obj-*的区别是什么？

usb-storage-obj-$(CONFIG_USB_STORAGE_DEBUG) += debug.o
当CONFIG_USB_STORAGE_DEBUG=y时  usb-storage-obj-y += debug.o
余下类似 

usb-storage-objs := scsiglue.o protocol.o transport.o usb.o 
initializers.o $(usb-storage-obj-y)

注意上面的‘’  把变量 usb-storage-obj-y 也做为usb-storage-objs依赖的条件了，也就引入了上面
debug.o等.o文件

给你一个牛人的网站看看：
http://blog.csdn.net/fudan_abc/category/655796.aspx