Android 与Linux Kernel


在kernel子目录下存放的就是Android的Linux Kernel了, 通过和标准的Linux 2.6.25 Kernel的对比,我们可以发现,其主要增加了以下的内容:
1. 基于ARM架构增加Gold-Fish平台,相应增加的目录如下:
kernel/arch/arm/mach-goldfish
kernel/include/asm-arm/arch-goldfish
Gold-Fish平台采用的是ARM926T CPU作为BaseBand处理器, 该CPU主频至少为200M HZ. 采用MSM7201A CPU(ARM 11)作为主CPU, 其主频为528M HZ.
2. 增加了yaffs2 FLASH文件系统,相应增加的目录为:
kernel/fs/yaffs2
实际上，Android包经过编译后生成的system.img和ramdisk.img文件就是yaffs2格式的包.
3. 增加了Android的相关Driver,相应目录为:
kernel/drivers/android
主要分为:
Android IPC系统: Binder
Android 日志系统: Logger
Android 电源管理: Power
Android 闹钟管理: Alarm
Android 内存控制台: Ram_console
Android 时钟控制的gpio: Timed_gpio
4. 增加了switch处理, 相应的目录为:
kernel/drivers/switch/
5. 增加了一种新的共享内存处理方式, 相应增加的文件为:
kernel/mm/ashmem.c
6. 其他为Linux-2.6.25内核所做的补丁等等，例如BlueTooth, 在此不做详细分析
另外GoldFish平台相关的驱动文件如下:
1. 字符输出设备:
kernel/drivers/char/goldfish_tty.c
2. 图象显示设备: (Frame Buffer)
kernel/drivers/video/goldfishfb.c
3. 键盘输入设备:
kernel/drivers/input/keyboard/goldfish_events.c
4. RTC设备: (Real Time Clock)
kernel/drivers/rtc/rtc-goldfish.c
. USB Device设备:
kernel/drivers/usb/gadget/android_adb.c
6. SD卡设备:
kernel/drivers/mmc/host/goldfish.c
7. FLASH设备:
kernel/drivers/mtd/devices/goldfish_nand.c
kernel/drivers/mtd/devices/goldfish_nand_reg.h
8. LED设备:
kernel/drivers/leds/ledtrig-sleep.c
9. 电源设备:
kernel/drivers/power/goldfish_battery.c
10. 音频设备:
kernel/arch/arm/mach-goldfish/audio.c
11. 电源管理:
kernel/arch/arm/mach-goldfish/pm.c
12. 时钟管理:
kernel/arch/arm/mach-goldfish/timer.c
以上为Android内核的大致分析，希望能给有兴趣的人员以简单帮助

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Goldfish Audio <-> arch/arm/mach-goldfish/audio.c
Goldfish pdev-bus <-> arch/arm/mach-goldfish/board-goldfish.c
                                        arch/arm/mach-goldfish/pdev_bus.c
Goldfish power management
                                <-> arch/arm/mach-goldfish/pm.c
Goldfish switch device(我觉得这是一个test device)
                                <-> arch/arm/mach-goldfish/switch.c
Goldfish timer         <-> arch/arm/mach-goldfish/timer.c
Goldfish tty             <-> drivers/char/goldfish_tty.c
Goldfish mmc(multi-media card)         
                               <-> drivers/mmc/host/goldfish.c
Goldfish keyboard <->drivers/input/keyboard/goldfish_events.c
Goldfish Nand        <-> drivers/mtd/devices/goldfish_nand.c
goldfish battery    <-> drivers/power/goldfish_battery.c
Goldfish rtc <-> drivers/rtc/rtc-goldfish.c
Goldfish framebuffer <-> drivers/video/goldfishfb.c 
And others:
        drivers/leds/ledtrig-sleep.c
        drivers/misc/lowmemorykiller.c
        drivers/misc/qemutrace/*
        drivers/switch/*
        
        
       

         Normally we can find all the device hardware info in the android-emulator/qemu/hw directory including goldfish_audio, goldfish_mmc, goldfish_nand, goldfish_tty, goldfish_events_device, goldfish_battery, goldfish_fb, goldfish_timer,goldfish_switch.

Android / Anonymous Shared Memory Subsystem, ashmem <-> mm/ashmem.c

drivers/android/(alarm.c binder.c logger.c power.c ram_console.c timed_gpio.c)


From android-emulator boot log
goldfish_add_device: goldfish_interrupt_controller, base ff000000 1000, irq 0 0
goldfish_add_device: goldfish_device_bus, base ff001000 1000, irq 1 1
goldfish_add_device: goldfish_timer, base ff003000 1000, irq 3 1
goldfish_add_device: goldfish_rtc, base ff010000 1000, irq 10 1
goldfish_add_device: goldfish_tty, base ff002000 1000, irq 4 1
goldfish_add_device: goldfish_tty, base ff011000 1000, irq 11 1
goldfish_add_device: smc91x, base ff012000 1000, irq 12 1
goldfish_add_device: goldfish_fb, base ff013000 1000, irq 13 1
goldfish_add_device: goldfish_memlog, base ff006000 1000, irq 0 0
goldfish_add_device: goldfish-battery, base ff014000 1000, irq 14 1
goldfish_add_device: goldfish_events, base ff015000 1000, irq 15 1
goldfish_add_device: goldfish_nand, base ff016000 1000, irq 0 0
goldfish_add_device: goldfish-switch, base ff017000 1000, irq 16 1
goldfish_add_device: goldfish-switch, base ff018000 1000, irq 17 1

In the end the Google Android use YAFFS2 file system which is a NAND file system, more info is here (http://discuz-android.blogspot.com/2008/01/yaffsyaffs2-and-jffs2-comparison.html)


drivers/char/goldfish_tty.c
drivers/char/Kconfig
config GOLDFISH_TTY
        tristate "Goldfish TTY Driver"
        default n
        help
                TTY driver for Goldfish Virtual Platform.

drivers/mmc/host/goldfish.c
drivers/mmc/host/Kconfig
config MMC_GOLDFISH
        tristate "goldfish qemu Multimedia Card Interface support"
        depends on ARCH_ANDROIDSIM
        help
                This selects the Goldfish Multimedia card Interface emulation.

                If unsure, say N.

drivers/input/keyboard/goldfish_events.c
drivers/input/keyboard/Kconfig
config KEYBOARD_GOLDFISH_EVENTS
        tristate "Generic Input Event device for Goldfish"
        help
                no help
                
drivers/mtd/devices/goldfish_nand.c
drivers/mtd/devices/goldfish_nand_reg.h
drivers/mtd/devices/Kconfig
config MTD_GOLDFISH_NAND
        tristate "Goldfish NAND device"
        help
                none

drivers/power/goldfish_battery.c
drivers/power/Kconfig
config BATTERY_GOLDFISH
        tristate "Goldfish battery driver"
        help
                Say Y to enable support for the battery and AC power in the Goldfish emulator.
                
drivers/rtc/rtc-goldfish.c
drivers/rtc/Kconfig
config RTC_DRV_GOLDFISH
        tristate "GOLDFISH"
        depends on RTC_CLASS
        help
          RTC driver for Goldfish Virtual Platform
          
drivers/video/goldfishfb.c 
drivers/video/Kconfig
config FB_GOLDFISH
        tristate "Goldfish Framebuffer
        depends on FB
        select FB_CFB_FILLRECT
        select FB_CFB_COPYAREA
        select FB_CFB_IMAGEBLIT
        ---help---
                Framebuffer driver for Goldfish Virtual Platform
                
mm/ashmem.c
mm/Makefile
        obj-$(CONFIG_ASHMEM) += ashmem.o

drivers/android/(alarm.c binder.c logger.c power.c ram_console.c timed_gpio.c)
drivers/Kconfig
source "drivers/android/Kconfig"
drivers/Makefile
obj-y                           += android/

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