config

CONFIG_ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE

功能介绍

atomic64自我测试代码用它来检查atomic64_dec_if_positive()函数是否可用。
The atomic64 self-test code uses CONFIG_ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE to check whether atomic64_dec_if_positive() is available.It seems it was needed when not every arch defined it. However as of current code the Kconfig option seems needless.

在kernel-fusion/config-4.10.0-25-generic中是否打开

无

代码位置

arch/parisc/Kconfig
lib/atomic64_test.c

相关代码分析

kernel-huawei/arch/parisc/Kconfig里没有此配置，kernel-android/arch/parisc/Kconfig中如下：

config ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
             def_bool y if GENERIC_ATOMIC64

而GENERIC_ATOMIC64在lib/Kconfig中，kernel-android与kernel-huawei下面两者一致，如下：

config GENERIC_ATOMIC64
       bool

lib/atomic64_test.c，kernel-android中的如下：

#ifdef CONFIG_ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
    INIT(onestwos);
    BUG_ON(atomic64_dec_if_positive(&v) != (onestwos - 1));
    r -= one;
    BUG_ON(v.counter != r);
    INIT(0);
    BUG_ON(atomic64_dec_if_positive(&v) != -one);
    BUG_ON(v.counter != r);
    INIT(-one);
    BUG_ON(atomic64_dec_if_positive(&v) != (-one - one));
    BUG_ON(v.counter != r);
#else
    #warning Please implement atomic64_dec_if_positive for your architecture and select the above Kconfig symbol
#endif

而kernel-huawei的则是去掉了第一行和最后三行。

修改建议

无需修改

CONFIG_BLK_DEV_RAM

功能介绍

设置为y意味着允许系统把一部分内存当作块设备(block device)使用，可以像使用块设备（比如硬盘）一样在上面建立文件系统、读写等操作。它一般在初次安装Linux时用于从软盘(floppy)上加载并存储一份最小根文件系统的拷贝。大部分用户不需要此功能，因此可以设置成“N”。（Saying Y here will allow you to use a portion of your RAM memory as a block device, so that you can make file systems on it, read and write to it and do all the other things that you can do with normal block devices (such as hard drives). It is usually used to load and store a copy of a minimal root file system off of a floppy into RAM during the initial install of Linux. ）

在kernel-fusion/config-4.10-25-generic中是否打开

无

代码位置

drivers/block/Kconfig

相关代码分析

kenel-andorid与kernel-huawei中一致，如下：

config BLK_DEV_RAM
    tristate "RAM block device support"
config BLK_DEV_RAM_COUNT
    int "Default number of RAM disks"
    default "16"
    depends on BLK_DEV_RAM
config BLK_DEV_RAM_SIZE
    int "Default RAM disk size (kbytes)"
    depends on BLK_DEV_RAM
    default "4096"
config BLK_DEV_RAM_DAX
    bool "Support Direct Access (DAX) to RAM block devices"
    depends on BLK_DEV_RAM && FS_DAX
    default n

修改建议

无需修改