第5章 Linux文件系統(tǒng)與設(shè)備文件系統(tǒng)

本章導(dǎo)讀

由于字符設(shè)備和塊設(shè)備都良好地體現(xiàn)了“一切都是文件”的設(shè)計(jì)思想，掌握Linux文件系統(tǒng)、設(shè)備文件系統(tǒng)的知識就顯得相當(dāng)重要了。

首先，驅(qū)動工程師編寫的驅(qū)動最終通過操作系統(tǒng)的文件操作系統(tǒng)調(diào)用或C庫函數(shù)（本質(zhì)也基于系統(tǒng)調(diào)用）被訪問，而設(shè)備驅(qū)動的結(jié)構(gòu)最終也是為了迎合提供給應(yīng)用程序員的API。

其次，驅(qū)動工程師在設(shè)備驅(qū)動中不可避免地會與設(shè)備文件系統(tǒng)打交道，從Linux2.4內(nèi)核的devfs文件系統(tǒng)到目前Linux2.6基于sysfs的udev文件系統(tǒng)。

5.1節(jié)講解了通過Linux API和C庫函數(shù)在用戶空間進(jìn)行Linux文件操作的編程方法。

5.2節(jié)分析了Linux文件系統(tǒng)的目錄結(jié)構(gòu)，簡單介紹了Linux內(nèi)核中文件系統(tǒng)的實(shí)現(xiàn)，并給出了文件系統(tǒng)與設(shè)備驅(qū)動的關(guān)系。

5.3節(jié)和5.4節(jié)分別講解Linux2.4內(nèi)核的devfs和Linux2.6所采用的udev設(shè)備文件系統(tǒng)，并分析了兩者的區(qū)別。

5.5節(jié)講解了LDD6410的SD卡和NAND分區(qū)和文件系統(tǒng)的使用情況。

        int creat(const char *filename, mode_t mode);

        int umask(int newmask);

        int open(const char *pathname, int flags);
        int open(const char *pathname, int flags, mode_t mode);

        open("test", O_CREAT, 10 705);

        open("test", O_CREAT, S_IRWXU | S_IROTH | S_IXOTH | S_ISUID );

        int read(int fd, const void *buf, size_t length);
        int write(int fd, const void *buf, size_t length);

        int open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);

        int lseek(int fd, offset_t offset, int whence);

        lseek(fd, -5, SEEK_CUR);

        lseek(fd, 0, SEEK_END);

        int close(int fd);

        1   #include <sys/types.h>
        2   #include <sys/stat.h>
        3   #include <fcntl.h>
        4   #include <stdio.h>
        5   #define LENGTH 100
        6   main()
        7   {
        8     int fd, len;
        9     char str[LENGTH];
        10
        11    fd = open("hello.txt", O_CREAT | O_RDWR, S_IRUSR | S_IWUSR); /*
        12    創(chuàng)建并打開文件 */
        13    if (fd) {
        14         write(fd, "Hello World", strlen("Hello World")); /*
        15         寫入字符串 */
        16         close(fd);
        17    }
        18
        19    fd = open("hello.txt", O_RDWR);
        20    len = read(fd, str, LENGTH); /* 讀取文件內(nèi)容 */
        21    str[len] = '\0';
        22    printf("%s\n", str);
        23    close(fd);
        24  }

        FILE *fopen(const char *path, const char *mode);

        int fgetc(FILE *stream);
        int fputc(int c, FILE *stream);
        char *fgets(char *s, int n, FILE *stream);
        int fputs(const char *s, FILE *stream);
        int fprintf(FILE *stream, const char *format, ...);
        int fscanf (FILE *stream, const char *format, ...);
        size_t fread(void *ptr, size_t size, size_t n, FILE *stream);
        size_t fwrite (const void *ptr, size_t size, size_t n, FILE *stream);

        int fgetpos(FILE *stream, fpos_t *pos);
        int fsetpos(FILE *stream, const fpos_t *pos);
        int fseek(FILE *stream, long offset, int whence);

        int fclose (FILE *stream);

        1   #include <stdio.h>
        2   #define LENGTH 100
        3   main()
        4   {
        5     FILE *fd;
        6     char str[LENGTH];
        7
        8     fd = fopen("hello.txt", "w+"); /* 創(chuàng)建并打開文件 */
        9     if (fd) {
        10        fputs("Hello World", fd); /* 寫入字符串 */
        11        fclose(fd);
        12    }
        13
        14    fd = fopen("hello.txt", "r");
        15    fgets(str, LENGTH, fd); /* 讀取文件內(nèi)容 */
        16    printf("%s\n", str);
        17    fclose(fd);
        18  }

        1  struct file
        2  {
        3    union {
        4     struct list_head fu_list;
        5     struct rcu_head fu_rcuhead;
        6    } f_u;
        7    struct dentry *f_dentry; /*與文件關(guān)聯(lián)的目錄入口(dentry)結(jié)構(gòu)*/
        8    struct vfsmount *f_vfsmnt;
        9    struct file_operations *f_op; /* 和文件關(guān)聯(lián)的操作*/
        10   atomic_t f_count;
        11   unsigned int f_flags;/*文件標(biāo)志，如O_RDONLY、O_NONBLOCK、O_SYNC*/
        12   mode_t f_mode; /*文件讀/寫模式，F(xiàn)MODE_READ和FMODE_WRITE*/
        13   loff_t f_pos; /* 當(dāng)前讀寫位置*/
        14   struct fown_struct f_owner;
        15   unsigned int f_uid, f_gid;
        16   struct file_ra_state f_ra;
        17
        18   unsigned long f_version;
        19   void *f_security;
        20
        21   /* tty驅(qū)動需要，其他的也許需要 */
        22   void *private_data; /*文件私有數(shù)據(jù)*/
        23   ...
        24   struct address_space *f_mapping;
        25 };

        if (file->f_mode & FMODE_WRITE) {/* 用戶要求可寫 */
        }
        if (file->f_mode & FMODE_READ) {/* 用戶要求可讀 */
        }

        if (file->f_flags & O_NONBLOCK)    /* 非阻塞 */
              pr_debug("open: non-blocking\n");
        else                                /* 阻塞 */
              pr_debug("open: blocking\n");

        1  struct inode {
        2     ...
        3     umode_t i_mode; /* inode的權(quán)限 */
        4     uid_t i_uid; /* inode擁有者的id */
        5     gid_t i_gid; /* inode所屬的群組id */
        6     dev_t i_rdev; /* 若是設(shè)備文件，此字段將記錄設(shè)備的設(shè)備號 */
        7     loff_t i_size; /* inode所代表的文件大小 */
        8
        9     struct timespec i_atime; /* inode最近一次的存取時(shí)間 */
        10    struct timespec i_mtime; /* inode最近一次的修改時(shí)間 */
        11    struct timespec i_ctime; /* inode的產(chǎn)生時(shí)間 */
        12
        13    unsigned long i_blksize; /* inode在做I/O時(shí)的區(qū)塊大小 */
        14    unsigned long i_blocks; /* inode所使用的block數(shù)，一個(gè)block為512 byte*/
        15
        16    struct block_device *i_bdev;
        17            /*若是塊設(shè)備，為其對應(yīng)的block_device結(jié)構(gòu)體指針*/
        18    struct cdev *i_cdev;   /*若是字符設(shè)備，為其對應(yīng)的cdev結(jié)構(gòu)體指針*/
        19    ...
        20 };

        unsigned int iminor(struct inode *inode);
        unsigned int imajor(struct inode *inode);

        Character devices:
          1 mem
          2 pty
          3 ttyp
          4 /dev/vc/0
          4 tty
          5 /dev/tty
          5 /dev/console
          5 /dev/ptmx
          7 vcs
          10 misc
          13 input
          21 sg
          29 fb
    128 ptm
    136 pts
    171 ieee1394
    180 usb
    189 usb_device
        Block devices:
          1 ramdisk
          2 fd
          8 sd
          9 md
    22 ide1
    ...

        crw-rw----   1 root    uucp      4,  64 Jan 30  2003 /dev/ttyS0
        brw-rw----   1 root    disk      8,   0 Jan 30  2003 /dev/sda

        /*創(chuàng)建設(shè)備目錄*/
        devfs_handle_t devfs_mk_dir(devfs_handle_t dir, const char *name, void *info);
        /*創(chuàng)建設(shè)備文件*/
        devfs_handle_t devfs_register(devfs_handle_t dir, const char *name, unsigned
          int flags, unsigned int major, unsigned int minor, umode_t mode, void *ops,
          void *info);
        /*撤銷設(shè)備文件*/
        void devfs_unregister(devfs_handle_t de);

        1   static devfs_handle_t devfs_handle;
        2   static int __init xxx_init(void)
        3   {
        4       int ret;
        5       int i;
        6       /*在內(nèi)核中注冊設(shè)備*/
        7       ret = register_chrdev(XXX_MAJOR, DEVICE_NAME, &xxx_fops);
        8       if (ret < 0) {
        9          printk(DEVICE_NAME " can't register major number\n");
        10         return ret;
        11      }
        12      /*創(chuàng)建設(shè)備文件*/
        13      devfs_handle =devfs_register(NULL, DEVICE_NAME, DEVFS_FL_DEFAULT,
        14      XXX_MAJOR, 0, S_IFCHR | S_IRUSR | S_IWUSR, &xxx_fops, NULL);
        15      ...
        16      printk(DEVICE_NAME " initialized\n");
        17      return 0;
        18  }
        19
        20  static void __exit xxx_exit(void)
        21  {
        22      devfs_unregister(devfs_handle); /*撤銷設(shè)備文件*/
        23      unregister_chrdev(XXX_MAJOR, DEVICE_NAME); /*注銷設(shè)備*/
        24  }
        25
        26  module_init(xxx_init);
        27  module_exit(xxx_exit);

        |-- block
        |   |-- fd0
        |   |-- md0
        |   |-- ram0
        |   |-- ram1
        |   |-- ...
        |-- bus
        |   |-- eisa
        |   |   |-- devices
        |   |   '-- drivers
        |   |-- ide
        |   |-- ieee1394
        |   |-- pci
        |   |   |-- devices
        |   |   |   |-- 0000:00:00.0 -> ../../../devices/pci0000:00/0000:00:00.0
        |   |   |   |-- 0000:00:01.0 -> ../../../devices/pci0000:00/0000:00:01.0
        |   |   |   |-- 0000:00:07.0 -> ../../../devices/pci0000:00/0000:00:07.0
        |   |   '-- drivers
        |   |      |-- PCI_IDE
        |   |      |   |-- bind
        |   |      |   |-- new_id
        |   |      |   '-- unbind
        |   |      '-- pcnet32
        |   |          |-- 0000:00:11.0 -> ../../../../devices/pci0000:00/0000:00:11.0
        |   |          |-- bind
        |   |          |-- new_id
        |   |          '-- unbind
        |   |-- platform
        |   |-- pnp
        |   '-- usb
        |      |-- devices
        |      '-- drivers
        |          |-- hub
        |          |-- usb
        |          |-- usb-storage
        |          '-- usbfs
        |-- class
        |   |-- graphics
        |   |-- hwmon
        |   |-- ieee1394
        |   |-- ieee1394_host
        |   |-- ieee1394_node
        |   |-- ieee1394_protocol
        |   |-- input
        |   |-- mem
        |   |-- misc
        |   |-- net
        |   |-- pci_bus
        |   |   |-- 0000:00
        |   |   |   |-- bridge -> ../../../devices/pci0000:00
        |   |   |   |-- cpuaffinity
        |   |   |   '-- uevent
        |   |   '-- 0000:01
        |   |      |-- bridge -> ../../../devices/pci0000:00/0000:00:01.0
        |   |      |-- cpuaffinity
        |   |      '-- uevent
        |   |-- scsi_device
        |   |-- scsi_generic
        |   |-- scsi_host
        |   |-- tty
        |   |-- usb
        |   |-- usb_device
        |   |-- usb_host
        |   '-- vc
        |-- devices
        |   |-- pci0000:00
        |   |   |-- 0000:00:00.0
        |   |   |-- 0000:00:07.0
        |   |   |-- 0000:00:07.1
        |   |   |-- 0000:00:07.2
        |   |   |-- 0000:00:07.3
        |   |-- platform
        |   |   |-- floppy.0
        |   |   |-- host0
        |   |   |-- i8042
        |   |-- pnp0
        |   '-- system
        |-- firmware
        |-- kernel
        |   '-- hotplug_seqnum
        |-- module
        |   |-- apm
        |   |-- autofs
        |   |-- cdrom
        |   |-- eisa_bus
        |   |-- i8042
        |   |-- ide_cd
        |   |-- ide_scsi
        |   |-- ieee1394
        |   |-- md_mod
        |   |-- ohci1394
        |   |-- parport
        |   |-- parport_pc
        |   |-- usb_storage
        |   |-- usbcore
        |   |   |-- parameters
        |   |   |-- refcnt
        |   |   '-- sections
        |   |-- virtual_root
        |   |   '-- parameters
        |   |      '-- force_probe
        |   '-- vmhgfs
        |      |-- refcnt
        |      '-- sections
        |          '-- __versions
        '-- power
            '-- state

        1  struct bus_type {
        2   const char        *name;
        3   struct bus_attribute  *bus_attrs;
        4   struct device_attribute    *dev_attrs;
        5   struct driver_attribute    *drv_attrs;
        6
        7   int (*match)(struct device *dev, struct device_driver *drv);
        8   int (*uevent)(struct device *dev, struct kobj_uevent_env *env);
        9   int (*probe)(struct device *dev);
        10  int (*remove)(struct device *dev);
        11  void (*shutdown)(struct device *dev);
        12
        13  int (*suspend)(struct device *dev, pm_message_t state);
        14  int (*suspend_late)(struct device *dev, pm_message_t state);
        15  int (*resume_early)(struct device *dev);
        16  int (*resume)(struct device *dev);
        17
        18  struct pm_ext_ops *pm;
        19
        20  struct bus_type_private *p;
        21 };
        22
        23 struct device_driver {
        24  const char        *name;
        25  struct bus_type       *bus;
        26
        27  struct module     *owner;
        28  const char        *mod_name;
        29
        30  int (*probe) (struct device *dev);
        31  int (*remove) (struct device *dev);
        32  void (*shutdown) (struct device *dev);
        33  int (*suspend) (struct device *dev, pm_message_t state);
        34  int (*resume) (struct device *dev);
        35  struct attribute_group **groups;
        36
        37  struct pm_ops *pm;
        38
        39  struct driver_private *p;
        40 };
        41
        42 struct device {
        43  struct klist      klist_children;
        44  struct klist_node knode_parent;
        45  struct klist_node knode_driver;
        46  struct klist_node knode_bus;
        47  struct device     *parent;
        48
        49  struct kobject kobj;
        50  char bus_id[BUS_ID_SIZE];  /* 在父總線中的位置 */
        51  const char        *init_name; /* 設(shè)備的初始名 */
        52  struct device_type    *type;
        53  unsigned     uevent_suppress:1;
        54
        55  struct semaphore  sem;
        56
        57  struct bus_type   *bus;         /* 設(shè)備所在的總線類型 */
        58  struct device_driver *driver;  /* 設(shè)備用到的驅(qū)動 */
        59  void     *driver_data;
        60  void     *platform_data;
        61  struct dev_pm_info    power;
        62
        63 #ifdef CONFIG_NUMA
        64  int      numa_node;
        65 #endif
        66  u64      *dma_mask;
        67  u64      coherent_dma_mask;
        68
        69  struct device_dma_parameters *dma_parms;
        70
        71  struct list_head  dma_pools;
        72
        73  struct dma_coherent_mem    *dma_mem;
        74
        75  struct dev_archdata   archdata;
        76
        77  spinlock_t        devres_lock;
        78  struct list_head  devres_head;
        79
        80  struct klist_node knode_class;
        81  struct class      *class;
        82  dev_t             devt;    /* dev_t, 創(chuàng)建sysfs "dev" */
        83  struct attribute_group**groups;
        84
        85  void(*release)(struct device *dev);
        86 };

        1  struct attribute {
        2         const char            *name;
        3         struct module          *owner;
        4         mode_t                mode;
        5  };
        6
        7  struct bus_attribute {
        8   struct attribute  attr;
        9   ssize_t (*show)(struct bus_type *bus, char *buf);
        10  ssize_t (*store)(struct bus_type *bus, const char *buf, size_t count);
        11 };
        12
        13 struct driver_attribute {
        14  struct attribute attr;
        15  ssize_t (*show)(struct device_driver *driver, char *buf);
        16  ssize_t (*store)(struct device_driver *driver, const char *buf,
        17             size_t count);
        18 };
        19
        20 struct device_attribute {
        21  struct attribute  attr;
        22  ssize_t (*show)(struct device *dev, struct device_attribute *attr,
        23            char *buf);
        24  ssize_t (*store)(struct device *dev, struct device_attribute *attr,
        25            const char *buf, size_t count);
        26 };

        1  # USB Epson printer to be called lp_epson
        2  LABEL, BUS="usb", serial="HXOLL0012202323480", NAME="lp_epson"
        3  # USB HP printer to be called lp_hp,
        4  LABEL, BUS="usb", serial="W09090207101241330", NAME="lp_hp"
        5  # sound card with PCI bus id 00:0b.0 to be the first sound card
        6  NUMBER, BUS="pci", id="00:0b.0", NAME="dsp"
        7  # sound card with PCI bus id 00:07.1 to be the second sound card
        8  NUMBER, BUS="pci", id="00:07.1", NAME="dsp1"
        9  # USB mouse plugged into the third port of the first hub to be
        10 # called mouse0
        11 TOPOLOGY, BUS="usb", place="1.3", NAME="mouse0"
        12 # USB tablet plugged into the second port of the second hub to be
        13 # called mouse1
        14 TOPOLOGY, BUS="usb", place="2.2", NAME="mouse1"
        15 # ttyUSB1 should always be called visor
        16 REPLACE, KERNEL="ttyUSB1", NAME="visor"

        SUBSYSTEM=="net", ACTION=="add", SYSFS{address}=="00:0d:87:f6:59:f3", IMPORT="/sbin/
    rename_netiface %k eth0"

        BUS="usb", SYSFS{serial}="HXOLL0012202323480", NAME="lp_epson", SYMLINK="printers/
    epson_stylus"

        Udevinfo starts with the device specified by the devpath and then
        walks up the chain of parent devices. It prints for every device
        found, all possible attributes in the udev rules key format.
        A rule to match, can be composed by the attributes of the device
        and the attributes from one single parent device.
          looking at device '/block/sda':
            KERNEL=="sda"
            SUBSYSTEM=="block"
            DRIVER==""
            ATTR{stat}=="    1 689     3 169    85 746    24 000     2 017     2 095    32 896
    47 292       0    23 188   71 292"
            ATTR{size}=="6 291 456"
            ATTR{removable}=="0"
            ATTR{range}=="16"
            ATTR{dev}=="8:0"
          looking at parent device '/devices/platform/host0/target0:0:0/0:0:0:0':
            KERNELS=="0:0:0:0"
            SUBSYSTEMS=="scsi"
            DRIVERS=="sd"
            ATTRS{ioerr_cnt}=="0x5"
            ATTRS{iodone_cnt}=="0xe86"
            ATTRS{iorequest_cnt}=="0xe86"
            ATTRS{iocounterbits}=="32"
            ATTRS{timeout}=="30"
            ATTRS{state}=="running"
            ATTRS{rev}=="1.0 "
            ATTRS{model}=="VMware Virtual S"
            ATTRS{vendor}=="VMware, "
            ATTRS{scsi_level}=="3"
            ATTRS{type}=="0"
            ATTRS{queue_type}=="none"
            ATTRS{queue_depth}=="3"
            ATTRS{device_blocked}=="0"
          looking at parent device '/devices/platform/host0/target0:0:0':
            KERNELS=="target0:0:0"
            SUBSYSTEMS==""
            DRIVERS==""
    looking at parent device '/devices/platform/host0':
        KERNELS=="host0"
        SUBSYSTEMS==""
        DRIVERS==""
    looking at parent device '/devices/platform':
        KERNELS=="platform"
        SUBSYSTEMS==""
        DRIVERS==""

        /bin/mount -t sysfs sysfs /sys
        /bin/mount -t tmpfs mdev /dev
        echo /bin/mdev > /proc/sys/kernel/hotplug
        mdev -s

        Command (m for help): p
        Disk /dev/sdb: 1 030 MB, 1 030 225 920 bytes
        32 heads, 62 sectors/track, 1 014 cylinders
        Units = cylinders of 1984 * 512 = 1 015 808 bytes
        Disk identifier: 0x6f20736b
            Device Boot     Start        End     Blocks   Id  System
        /dev/sdb1   *          1          20       19 809   83  Linux
        /dev/sdb2            21        1014      98 6048  83  Linux

        Command (m for help): n
        Command action
          e   extended
          p   primary partition (1-4)
        p
        Partition number (1-4): 1
        First cylinder (1-1 014, default 1):
        Using default value 1
        Last cylinder, +cylinders or +size{K,M,G} (1-1 014, default 1 014): 20M

        Command (m for help): n
        Command action
          e   extended
          p   primary partition (1-4)
        p
        Partition number (1-4): 2
        First cylinder (21-1 014, default 21):
        Using default value 21
        Last cylinder, +cylinders or +size{K,M,G} (21-1 014, default 1 014):
        Using default value 1 014
        Command (m for help):

        Command (m for help): a
        Partition number (1-4): 1

        mkfs.vfat /dev/sdb1
        mkfs.ext3 /dev/sdb2
        fsck.ext3 /dev/sdb2

        cp -fa <your-rootfs> <sdb2-mount-point>

        struct mtd_partition s3c_partition_info[] = {
                    {
                                .name        = "Bootloader",
                                .offset      = 0,
                                .size        = (512*SZ_1K),
                    },
                    {
                                .name        = "Kernel",
                                .offset      = (512*SZ_1K),
                                .size        = (4*SZ_1M) - (512*SZ_1K),
                    },
                    {
                                .name        = "File System",
                                .offset      = MTDPART_OFS_APPEND,
                                .size        = MTDPART_SIZ_FULL,
                  }
        };

        # tftp -r u-boot-movi.bin -g 192.168.1.111

        # flashcp u-boot-movi.bin /dev/mtd0

        # tftp -r zImage-fix -g 192.168.1.111

        # flashcp zImage-fix /dev/mtd1

        # flash_eraseall /dev/mtd2

        # mount /dev/mtdblock2 -t yaffs2 /mnt/

        # cp -fa <new_rootfs_dir> /mnt

        # mdev -s

        #1s
        android                    init.rc                    sbin
        bin                        lib                        sqlite_stmt_journals
        cache                           linuxrc                         sys
        data                            lost+found                      system
        demo                            mnt                             tmp
        dev                             opt                             usr
        etc                             proc                            var
        init.goldfish.rc                qtopia

        # cd /demo/
        # jpegview 1.jpg 2.jpg 3.jpg 4.jpg
        480 272 480 544 0 272 16 0 480 272
        framebase = 0x4016c000 err=0
        ImageWidth=362 ImageHeight=272
        read 1.jpg OK
        ImageWidth=362 ImageHeight=272
        read 2.jpg OK
        ImageWidth=362 ImageHeight=272
        read 3.jpg OK
        ImageWidth=362 ImageHeight=272
        read 4.jpg OK