linux error note

undefined reference to `wrong_size_cmpxchg'?

reason:gcc 版本不兼容，更换新版试试  

在开发板和LINUX间用NFS挂载已成功，但文件却看不到？

reason：开发板上的NFS 版本与你PC机上的不兼容，挂载时加个OPTION nfsvers=版本号（4，3，2）

man 5 nfs 查看了下nfsvers=n 的说明如下：

nfsvers=n The NFS protocol version number used to  

contact the server's NFS service. If the  

server does not support the requested ver‐  

sion, the mount request fails. If this  

option is not specified, the client negoti‐  

ates a suitable version with the server,  

trying version 4 first, version 3 second,  

and version 2 last.
  

下载自己裁减编译好的内核zImage启动后出现：

    List of all partitions:  

    1f00            1024 mtdblock0 (driver?)  

    1f01            3840 mtdblock1 (driver?)  

    1f02            3072 mtdblock2 (driver?)  

    1f03           61440 mtdblock3 (driver?)  

    1f04           61440 mtdblock4 (driver?)  

    No filesystem could mount root, tried:  ext3 ext2 cramfs vfat msdos iso9660 romfs  

    Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(31,3)  

reason:内核没有添加对YAFFS2的支持，添加。。后来看了看自己的配置其实是添加了的，但还是有问题，我就直接保存成.config 再编译。ok

综上所述得知更改的配置并没有保存在.config中(我是用make s3c2410_defconf 加载的默认配置改的，改好自己保存成一个配置文件 ，后面是用LOAD加载进来的，改后直接 保存了就make zImage,结果怎么都不成功。不知道什么BUG)

写宏遇到的问题：warning: backslash and newline separated by space

reason:'\'符号后面多了空格，删除空格就OK

在编译2440的内核时遇到如下问题：

drivers/net/cs8900.c: In function `cs8900_probe':  

drivers/net/cs8900.c:461: error: `S3C2410_GPGCON' undeclared (first use in this function)  

drivers/net/cs8900.c:461: error: (Each undeclared identifier is reported only once  

drivers/net/cs8900.c:461: error: for each function it appears in.)  

drivers/net/cs8900.c:462: error: `S3C2410_EXTINT1' undeclared (first use in this function)  

drivers/net/cs8900.c:463: error: `S3C2410_BWSCON' undeclared (first use in this function)  

drivers/net/cs8900.c:464: error: `S3C2410_BANKCON3' undeclared (first use in this function)  

drivers/net/cs8900.c:461: warning: statement with no effect  

drivers/net/cs8900.c:462: warning: statement with no effect  

drivers/net/cs8900.c:463: warning: statement with no effect  

drivers/net/cs8900.c:464: warning: statement with no effect  

make[2]: *** [drivers/net/cs8900.o] Error 1  

make[1]: *** [drivers/net] Error 2  

  reason:S3C2410的宏没定义，检查发现编译2440内核时需要选中system type->s3c2410 machines->SMDK2410/A9M2410

编译出的内核    ls /dev下有一堆的tty,pty端口，如何减少这些端口？

u盘无法挂载?

# Warning: could not register server
usb 1-1.2: new full speed USB device using s3c2410-ohci and address 3
usb 1-1.2: configuration #1 chosen from 1 choice
scsi0 : SCSI emulation for USB Mass Storage devices
usb 1-1.2: New USB device found, idVendor=0781, idProduct=5567
usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 1-1.2: Product: Firebird USB Flash Drive
usb 1-1.2: Manufacturer: SanDisk
usb 1-1.2: SerialNumber: 4C532000051130122550
QDir::readDirEntries: Cannot read the directory: /usr/lib/ipkg/externinfo
scsi 0:0:0:0: Direct-Access     SanDisk  Cruzer Blade     1.26 PQ: 0 ANSI: 5
sd 0:0:0:0: [sda] 15633408 512-byte hardware sectors: (8.00 GB/7.45 GiB)
sd 0:0:0:0: [sda] Write Protect is off
sd 0:0:0:0: [sda] Assuming drive cache: write through
sd 0:0:0:0: [sda] 15633408 512-byte hardware sectors: (8.00 GB/7.45 GiB)
sd 0:0:0:0: [sda] Write Protect is off
sd 0:0:0:0: [sda] Assuming drive cache: write through
sda:<7>usb-storage: queuecommand called
   sda1
sd 0:0:0:0: [sda] Attached SCSI removable disk
sd 0:0:0:0: Attached scsi generic sg0 type 0
  

如下命令查询
# cat /proc/partitions
major minor  #blocks  name
  31        0       1024 mtdblock0
  31        1       3840 mtdblock1
  31        2       3072 mtdblock2
  31        3      61440 mtdblock3
  31        4      61440 mtdblock4
   8        0    7816704 sda
   8        1    7816688 sda1
# ls /dev/sda
ls: /dev/sda: No such file or directory
dev/下没有sda设备。。
  

注：检查发现U盘的支持不仅要usb massive storage, scsi, msdos partition/ filesystem，还要加入对应文件系统的language编码支持
(437) Default codepage for FAT                --------------------------必须选中  Codepage 437  (United States,Canada)
(iso8859-1) Default iocharset for FAT    -------------------------必须选中   NLS ISO 8859-1 (Latin 1; Western European Languages
  

打开dev/fb0时老是出错，fd_fb = open("/dev/fb0", O_RDWR);返回-1

VIDIOC_S_FMT failed (-1)

       Capability Informations:
        driver: uvcvideo
        card: USB2.0 PC Camera
        bus_info: usb-0000:02:03.0-1
        version: 3.5.7
        capabilities: 04000001
        VIDIOC_S_FMT failed (-1)
  

在写图片保存文件时遇到错误，总是无法生成正解的BMP格式 ，查看产生的图片文件数据发现总是多了两个字节。

对比相同大小和位色的图片发现在类型属性后面总是多出两字节，正常的BMP格式头部信息应该是14+40=54个字节，结果此处却是56，追查发现是
sizeof（BITMAPFILEHEADER）＝16 但

     typedef unsigned short int WORD;  

     typedef unsigned long int DWORD;  

     typedef long int LONG;  

     /* Header of the bitmap file */  

     typedef struct {  

       WORD bfType;			  

       DWORD bfSize;		  

       WORD bfReserved1;	  

       WORD bfReserved2;		  

       DWORD bfOffBits;	  

     } BITMAPFILEHEADER;  

读出sizeof（WORD）＝2，sizeof（DWORD）＝4   那此处 sizeof（BITMAPFILEHEADER）＝14 才应该是对的，可无论怎样都是16
MSDN:When applied to a structure type or variable, sizeof returns the actual size, which may include padding bytes inserted for alignment.
多出来的是padding bytes，为了对齐出现的，如何解决？

• 使用#pragma pack(n)来设定变量以n字节对齐方式 eg:
  

  <span style="color:#3333FF;">#pragma pack(push,1)</span>
  typedef struct {
  WORD bfType;
  DWORD bfSize;
  WORD bfReserved1;
  WORD bfReserved2;
  DWORD bfOffBits;
  } BITMAPFILEHEADER;
  <span style="color:#3333FF;">#pragma pack(pop)</span>

• 使用__attribute__属性
  

  struct my_align_struct {
    uint32 u0:8;
    uint32 u1:8;
    uint32 u2:8;
    uint32 u3:16;
  }__attribute__((packed, aligned(1)))

nfs挂载错误:wrong fs type, bad option, bad superblock

'mount.nfs: Protocol not supported'

Makefile:492: recipe for target 'menuconfig' failed ,Unable to find the ncurses libraries or the required header files.

make bzImage 时 fatal error: linux/compiler-gcc5.h: No such file or directory

Makefile:1607 *** mixed implicit and nomal rules:depracated syntax

yaffs2移植出错

下载最新版源码git clonegit://www.aleph1.co.uk/yaffs2，打补丁，刚开始时打补丁用的命令是：

./patch-ker.sh c s  /root/linux-test/linux-2.6.32.2，后来出错建议我s 改用m，内核版本太低只能用m,改正好OK，之后配置编译时却出了一堆问题：

fs/yaffs2/yaffs_vfs.c:66:26: error: yaffs_mtdif1.h: No such file or directory
fs/yaffs2/yaffs_vfs.c:67:26: error: yaffs_mtdif2.h: No such file or directory
fs/yaffs2/yaffs_vfs.c: In function 'yaffs_link':
fs/yaffs2/yaffs_vfs.c:309: error: implicit declaration of function 'set_nlink'
fs/yaffs2/yaffs_vfs.c: In function 'yaffs_setattr':

处理方法，删除原来的yaffs2文件，重新打补丁./patch-ker.sh c m  /root/linux-test/linux-2.6.32.2,
错误原因：第一次打补丁时用的s参数，后来虽然改了m，但先前的文件却是保留下来了。

uvc驱动是正常的，在PC机上插入拔出USB camera会自动创建与删除设备结点，但到开发板上却只有在启动时插上才会自动创建/dev/video0，拔掉也不会知道删除？

百度查询得知：要想自动创建设备结点，不仅要驱动中利用udev（mdev）来实现设备文件的自动创建，还要文件系统支持udev(mdev)才行，坑爹的飞凌板子里的文件系统不支持，所以一直不能自动创建 ，还以为是我UVC驱动移植错了。。对busybox配置加入mdev机制，编译自己的文件系统。

经验证直接用飞凌现有的文件系统更改下 /linuxrc 文件重启后就可以了。
#!/bin/sh
#echo "mount /etc as ramfs"
#/bin/mount -n -t ramfs ramfs /etc
#/bin/cp -a /mnt/etc/* /etc

#/bin/mount -n -t ramfs ramfs /var/state/dhcp
#/bin/mount -n -t ramfs ramfs /var/log/boa
#/bin/mount -n -t ramfs ramfs /usr/Setting
#/bin/cp -a /mnt/Setting/* /usr/Setting

#/bin/mount -n -t ramfs ramfs /tmp
#/bin/cp -a /mnt/etc/* /etc

/bin/mount -t proc proc /proc
/bin/mount -t sysfs sysfs /sys
/bin/mount -t tmpfs tmpfs /dev
mkdir /dev/pts
mkdir /dev/shm

/bin/echo /sbin/mdev > /proc/sys/kernel/hotplug
/sbin/mdev -s

exec /sbin/init
可参考：http://blog.csdn.net/geekcome/article/details/6570072

使用servfox做网络视频时老是出“Couldnt set videopict params with VIDIOCSPICT”

查看了下VIDIOCSPICT的定义原来只能在V4L1中支持，在V4L2中是不支持这个定义的原文说明“V4L2 has no equivalent of theVIDIOCGPICT andVIDIOCSPICTioctl and structvideo_picture”，https://linuxtv.org/downloads/v4l-dvb-apis/compat.html#id-1.4.10.3.13   
在驱动中选中兼容v4l1也不行，搜了一堆也没用，只能改servfox的代码，工程太大对于我们这种菜鸟来说就放弃吧，
工作还是要继续的，天不负苦心人呀，找个Mjpg-stream是可以的。mjpg-stream移植请见http://www.embedu.org/column/Column331.htm

正解是：ln -sfn 目标   待更新的旧链接     ，n的意思自己man ln看吧

/libtool: line 950: arm-none-linux-gnueabi-ranlib: command not found
make[1]: *** [install-libLTLIBRARIES] Error 127