linux串口终端设备驱动分析

 17.内核启动信息分析
      Uncompressing Linux......................................................
      done          
      , booting the kernel.                                             
      [archarmootcompressedmisc.c: decompress_kernel()]
      Linux version 2.6.24.4 (root@localhost.localdomain) (gcc version 4.1.2) #7

      Tue Apr 15 07:50:25 CST 2008                                              
                                             [init/main.c :start_kernel]
      CPU: ARM920T [41129200] revision 0 (ARMv4T), cr=c0007177                  
      [start_kernel->setup_arch->setup_processor]
      Machine: SMDK2410                                                         
                                       [setup_arch->setup_machine]
      Converting old-style param struct to taglist                              
         [setup_arch->convert_to_tag_list->..->build_tag_list]
      ATAG_INITRD is deprecated; please update your bootloader.                 
           [setup_arch->parse_tags->parse_tag_initrd ]
      Memory policy: ECC disabled, Data cache writeback                         
      [setup_arch->paging_init->build_mem_type_table]
      On node 0 totalpages: 16384  
      [setup_arch->paging_init->bootmem_init_node->free_area_init_node->
      calculate_node_totalpages]
         DMA zone: 128 pages used for memmap                       
      [setup_arch->..->free_area_init_node->free_area_init_core]
         DMA zone: 0 pages reserved
         DMA zone: 16256 pages, LIFO batch:3
         Normal zone: 0 pages used for memmap
         Movable zone: 0 pages used for memmap
      CPU S3C2440A (id 0x32440001)
      [setup_arch->paging_init->devicemaps_init->mdesc->smdk2410_map_io->s3c24xx_init_io]
      S3C244X: core 400.000 MHz, memory 100.000 MHz, peripheral 50.000 MHz
      [..smdk2410_map_io->cpu_ids->s3c244x_init_clocks]
      S3C24XX Clocks, (c) 2004 Simtec Electronics                               
             [...s3c244x_init_clocks->s3c24xx_setup_clocks]
      CLOCK: Slow mode (1.500 MHz), fast, MPLL on, UPLL on                      
         [...s3c244x_init_clocks->s3c2410_baseclk_add]
      CPU0: D VIVT write-back cache                                             
                        [setup_arch->cpu_init->dump_cpu_info]
      CPU0: I cache: 16384 bytes, associativity 64, 32 byte lines, 8 sets
      CPU0: D cache: 16384 bytes, associativity 64, 32 byte lines, 8 sets
      Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 16256
                              [start_kernel->build_all_zonelists]
      Kernel command line: root=/dev/ram init=/linuxrc
      initrd=0x30a00000,0x00100000                  [start_kernel, print cmd
      line ]
      console=ttySAC1,115200 mem=65536K devfs=mount
      irq: clearing pending ext status 000dff00         
      [start_kernel->init_IRQ->init_arch_irq(mdesc->init_irq)->s3c24xx_init_irq]
      irq: clearing pending ext status 00001000          [init_arch_irq
      在arm体系下是一个函数指针,setup_arch初始化其为mdesc->init_irq]
      irq: clearing subpending status 0000009a
      irq: clearing subpending status 00000092
      PID hash table entries: 256 (order: 8, 1024 bytes) 
      [start_kernel->pidhash_init]
      timer tcon=00090000, tcnt a2c1, tcfg 00000200,00000000, usec 00001eb8 
      [start_kernel->time_init->system_timer.init->
                                                                                
                             s3c2410_timer_init->s3c2410_timer_setup]
              [setup_arch中初始化全局函数指针 system_timer = mdesc->timer ,既s3c24xx_timer,
      arch/arm/plat-s3c24xx/timer.c]
      Console: colour dummy device 80x30               
      [start_kernel->console_init-> via lds __con_initcall_start ->vt:con_init]
      selected clock c0239b70 (pclk) quot 26, calc 115740
      [console_initcall(s3c24xx_serial_initconsole)->register_console->console.setup->
      s3c24xx_serial_console.setup(s3c24xx_serial_console_setup)->uart_set_options->s3c24xx_serial_set_termios->s3c24xx_serial_getclk]console
      [ttySAC1] enabled                            
      [console_initcall(s3c24xx_serial_initconsole)->register_console]
      Dentry cache hash table entries: 8192 (order: 3, 32768 bytes)             
                                  [start_kernel->vfs_caches_init_early]
      Inode-cache hash table entries: 4096 (order: 2, 16384 bytes)
      Memory: 64MB = 64MB total                                                 
                                                                
      [start_kernel->mem_init]
      Memory: 61440KB available (2060K code, 248K data, 108K init)
      Calibrating delay loop... 199.47 BogoMIPS (lpj=498688)                    
                                             [start_kernel->calibrate_delay]
      Mount-cache hash table entries: 512                                &n bsp;
                                          [start_kernel->
      vfs_caches_init->mnt_init]
      CPU: Testing write buffer coherency: ok                                   
      [start_kernel->check_bugs->check_writebuffer_bugs]
      net_namespace: 64 bytes                  
      [start_kernel->rest_init->kernel_init->do_basic_setup->pure_initcall(net_ns_init)]
      NET: Registered protocol family 16                                        
                  [core_initcall(netlink_proto_init)->sock_register]
      S3C2440: Initialising architecture                         
      [arch_initcall(s3c_arch_init)->(cpu->init())->cpu_ids->s3c2410_init]
      S3C2440: IRQ Support            
      [arch_initcall(s3c2440_irq_init)->sysdev_driver_register->drv.add()->s3c2440_irq_add]
      S3C2440: Clock Support, DVS off                         
      [arch_initcall(s3c24xx_clk_driver)->s3c2440_clk_driver.s3c2440_clk_add]
      S3C24XX DMA Driver, (c) 2003-2004,2006 Simtec Electronics      
      [arch_initcall(s3c2410_dma_drvinit)->sysdev_driver_register->
      DMA channel 0 at c4800000, irq 33             
      c2410_dma_driver.s3c2410_dma_add->s3c2410_dma_init->s3c24xx_dma_init]
      DMA channel 1 at c4800040, irq 34
      DMA channel 2 at c4800080, irq 35
      DMA channel 3 at c48000c0, irq 36
      usbcore: registered new interface driver usbfs  
      [subsys_initcall(usb_init)->usb_register(&usbfs_driver)->usb_register_driver]
      usbcore: registered new interface driver hub   
      [subsys_initcall(usb_init)->usb_hub_init(&hub_driver)->usb_register_driver]
      usbcore: registered new device driver usb       
      [subsys_initcall(usb_init)->usb_register_device_driver(&usb_generic_driver)]
      NET: Registered protocol family 2                                         
                                                   
      [fs_initcall(inet_init)->sock_register]
      IP route cache hash table entries: 1024 (order: 0, 4096 bytes)            
                         [fs_initcall(inet_init)->ip_init->ip_rt_init ]
      TCP established hash table entries: 2048 (order: 2, 16384 bytes)   
      [fs_initcall(inet_init)->ip_init->tcp_init]
      TCP bind hash table entries: 2048 (order: 1, 8192 bytes)               
      [fs_initcall(inet_init)->ip_init->tcp_init]
      TCP: Hash tables configured (established 2048 bind 2048)             
      [fs_initcall(inet_init)->ip_init->tcp_init]
      TCP reno registered                             
      [fs_initcall(inet_init)->ip_init->tcp_init->tcp_register_congestion_control]
      checking if image is initramfs...<5>it isn't (no cpio magic); looks like
      an initrd                  [rootfs_initcall(populate_rootfs)]
      Freeing initrd memory: 1024K             
      [rootfs_initcall(populate_rootfs)->free_initrd->free_initrd_mem->free_area]
      NetWinder Floating Point Emulator V0.97 (extended precision) 
      [module_init(fpe_init);]
      JFFS2 version 2.2. (NAND) 漏 2001-2006 Red Hat, Inc.   
      [module_init(init_jffs2_fs);]
      io scheduler noop registered                           
      [module_init(noop_init)->elv_register]
      io scheduler anticipatory registered (default)                     
      [module_init(as_init)->elv_register]
      io scheduler deadline registered                    
      [module_init(deadline_init)->elv_register]
      io scheduler cfq registered                                             
      [module_init(cfq_init)->elv_register]
      Serial: 8250/16550 driver $Revision: 1.90 $ 4 ports, IRQ sharing enabled  
               [ module_init(serial8250_init)]
      s3c2440-uart.0: s3c2410_serial0 at MMIO 0x50000000 (irq = 70) is a S3C2440
      [module_init(s3c24xx_serial_modinit)->s3c2440_serial_init->
      s3c2440-uart.1: s3c2410_serial1 at MMIO 0x50004000 (irq = 73) is a S3C2440
       s3c2440_serial_probe->uart_add_one_port->
      s3c2440-uart.2: s3c2410_serial2 at MMIO 0x50008000 (irq = 76) is a S3C2440
       uart_configure_port->uart_report_port]
      RAMDISK driver initialized: 2 RAM disks of 4096K size 1024 blocksize      
                                              [module_init(rd_init);]
      loop: module loaded                                                       
                                                            
      [module_init(loop_init);]
      S3C24XX NAND Driver, (c) 2004 Simtec Electronics                          
                     [module_init(s3c2410_nand_init);]
      s3c2440-nand s3c2440-nand: Tacls=3, 30ns Twrph0=7 70ns, Twrph1=3 30ns 
      [s3c2440_nand_probes->3c2410_nand_inithw]
      NAND device: Manufacturer ID: 0xec, Chip ID: 0x76 (Samsung NAND 64MiB 3,3V
      8-bit) [ form above...->nand_scan_ident nand_get_flash_type]
      Scanning device for bad blocks   [s3c24xx_nand_probe->nand_scan
      ->nand_scan_tail->chip->scan_bbt:..->create_bbt]
      Creating 4 MTD partitions on "NAND 64MiB 3,3V 8-bit":                     
       [s3c2410_nand_add_partition->add_mtd_partitions]
      0x00000000-0x00030000 : "Boot Agent"
      0x00030000-0x00200000 : "kernel"
      0x00200000-0x02000000 : "ramfs"
      0x02000000-0x04000000 : "extfs"
      ohci_hcd: 2006 August 04 USB 1.1 'Open' Host Controller (OHCI) Driver
      ohci_hcd: block sizes: ed 64 td 64
      s3c2410-ohci s3c2410-ohci: s3c2410_start_hc:
      s3c2410-ohci s3c2410-ohci: S3C24XX OHCI
      s3c2410-ohci s3c2410-ohci: new USB bus registered, assigned bus number 1
      s3c2410-ohci s3c2410-ohci: irq 42, io mem 0x49000000
      s3c2410-ohci s3c2410-ohci: created debug files
      s3c2410-ohci s3c2410-ohci: OHCI controller state
      s3c2410-ohci s3c2410-ohci: OHCI 1.0, NO legacy support registers
      s3c2410-ohci s3c2410-ohci: control 0x083 HCFS=operational CBSR=3
      s3c2410-ohci s3c2410-ohci: cmdstatus 0x00000 SOC=0
      s3c2410-ohci s3c2410-ohci: intrstatus 0x00000004 SF
      s3c2410-ohci s3c2410-ohci: intrenable 0x8000005a MIE RHSC UE RD WDH
      s3c2410-ohci s3c2410-ohci: hcca frame #001e
      s3c2410-ohci s3c2410-ohci: roothub.a 02001202 POTPGT=2 NOCP NPS NDP=2(2)
      s3c2410-ohci s3c2410-ohci: roothub.b 00000000 PPCM=0000 DR=0000
      s3c2410-ohci s3c2410-ohci: roothub.status 00008000 DRWE
      s3c2410-ohci s3c2410-ohci: roothub.portstatus [0] 0x00000100 PPS
      s3c2410-ohci s3c2410-ohci: roothub.portstatus [1] 0x00000100 PPSu
      sb usb1: default language 0x0409
      usb usb1: uevent
      usb usb1: usb_probe_device
      usb usb1: configuration #1 chosen from 1 choice
      usb usb1: adding 1-0:1.0 (config #1, interface 0)
      usb 1-0:1.0: uevent
      hub 1-0:1.0: usb_probe_interface
      hub 1-0:1.0: usb_probe_interface - got id
      hub 1-0:1.0: USB hub found
      s3c2410-ohci s3c2410-ohci:
      s3c2410_hub_control(c3c2b400,0xa006,0x2900,0x0000,c3c19a84,000f)
      hub 1-0:1.0: 2 ports detected
      hub 1-0:1.0: standalone hub
      hub 1-0:1.0: no power switching (usb 1.0)
      hub 1-0:1.0: no over-current protection
      hub 1-0:1.0: power on to power good time: 4ms
      s3c2410-ohci s3c2410-ohci:
      s3c2410_hub_control(c3c2b400,0xa000,0x0000,0x0000,c3c19a40,0004)
      hub 1-0:1.0: local power source is good
      hub 1-0:1.0: trying to enable port power on non-switchable hub
      s3c2410-ohci s3c2410-ohci:
      s3c2410_hub_control(c3c2b400,0x2303,0x0008,0x0001,c3c19a40,0000)
      s3c2410-ohci s3c2410-ohci:
      s3c2410_hub_control(c3c2b400,0x2303,0x0008,0x0002,c3c19a40,0000)
      hub 1-0:1.0: state 7 ports 2 chg 0000 evt 0000
      usb usb1: new device strings: Mfr=3, Product=2, SerialNumber=1
      usb usb1: Product: S3C24XX OHCI
      usb usb1: Manufacturer: Linux 2.6.24.4 ohci_hcd
      usb usb1: SerialNumber: s3c24xx
      s3c2410_udc: debugfs dir creation failed -19
      s3c2410-ohci s3c2410-ohci:
      s3c2410_hub_control(c3c2b400,0xa300,0x0000,0x0001,c3c6fe30,0004)
      s3c2410-ohci s3c2410-ohci:
      s3c2410_hub_control(c3c2b400,0xa300,0x0000,0x0002,c3c6fe30,0004)
      mice: PS/2 mouse device common for all mice                       
      [module_init(mousedev_init);]
      S3C24XX RTC, (c) 2004,2006 Simtec Electronics                      
      [module_init(s3c_rtc_init);]
      s3c2440-i2c s3c2440-i2c: slave address 0x10   
      [s3c2440_i2c_driver.s3c24xx_i2c_probe->s3c24xx_i2c_init]
      s3c2440-i2c s3c2440-i2c: bus frequency set to 390 KHz   [同上]
      s3c2440-i2c s3c2440-i2c: i2c-0: S3C I2C adapter                          
      [s3c2440_i2c_driver.s3c24xx_i2c_probe]
      S3C2410 Watchdog Timer, (c) 2004 Simtec Electronics  
      [module_init(watchdog_init);]
      s3c2410-wdt s3c2410-wdt: watchdog inactive, reset disabled, irq enabled
      TCP cubic registered         
      [module_init(cubictcp_register)->tcp_register_congestion_control]
      drivers/rtc/hctosys.c: unable to open rtc device (rtc0)  
      [late_initcall(rtc_hctosys)]
      RAMDISK: Compressed image found at block 0 
      [kernel_init->prepare_namespace->initrd_load->rd_load_image->identify_ramdisk_image]
      VFS: Mounted root (ext2 filesystem).     
      [kernel_init->prepare_namespace->mount_root->mount_block_root->do_mount_root]
      Freeing init memory: 108K
      selected clock c0239b70 (pclk) quot 26, calc 115740  /*以下内容为busybox产生*/
      selected clock c0239b70 (pclk) quot 26, calc 115740
      init started: BusyBox v1.10.1 (2008-04-19 15:27:01 CST)
      selected clock c0239b70 (pclk) quot 26, calc 115740
      starting pid 225, tty '': '/etc/init.d/rcS'
      Open ARM AKAE-www.linuxforum.net
      Start mdev...
      mount: mounting sysfs on /sys failed: Device or resource busy
      selected clock c0239b70 (pclk) quot 26, calc 115740
      starting pid 236, tty '/dev/console': '-/bin/sh '
      BusyBox v1.10.1 (2008-04-19 15:27:01 CST) built-in shell (msh)
      Enter 'help' for a list of built-in commands.
      --------------------------------------------------------------------------------
      18 .Uart devices register and driver select

      1.machine和cpu的检测与uart设备名的设置
      CPU S3C2440A (id 0x32440001)
      [setup_arch->paging_init->devicemaps_init->mdesc->smdk2410_map_io->s3c24xx_init_io]
        
      mdesc是SMDK2410,smdk2410_map_io->s3c24xx_init_io根据cpuid设置arm/plat-s3c24xx的全局变量cpu.然后mdk2410_map_io
      调用s3c24xx_init_uarts(smdk2410_uartcfgs,
      ARRAY_SIZE(smdk2410_uartcfgs));通过(cpu->init_uarts)(cfg,
      no);注册cpu特的定的uart资源.
      cpu_ids在arch/arm/plat-s3c24xx/cpu.c中,其中2440a的uart初始化函数是:

      void __init s3c244x_init_uarts(struct s3c2410_uartcfg *cfg, int no)
      {
          s3c24xx_init_uartdevs("s3c2440-uart", s3c2410_uart_resources, cfg,
no);
      }
      void __init s3c24xx_init_uartdevs(char *name,
                        struct s3c24xx_uart_resources *res,
                        struct s3c2410_uartcfg *cfg, int no)
      {
          struct platform_device *platdev;
          struct s3c2410_uartcfg *cfgptr = uart_cfgs;
          struct s3c24xx_uart_resources *resp;
          int uart;
          memcpy(cfgptr, cfg, sizeof(struct s3c2410_uartcfg) * no);
          for (uart = 0; uart < no; uart++, cfg++, cfgptr++) {
              platdev = s3c24xx_uart_src[cfgptr->hwport];
              resp = res + cfgptr->hwport;
              s3c24xx_uart_devs[uart] = platdev;  /*uart的platform设备*/
              platdev->name = name;   /*platform 设备名称初始化为 "s3c2440-uart" */
              platdev->resource = resp->resources;
              platdev->num_resources = resp->nr_resources;
              platdev->dev.platform_data = cfgptr;
          }
          nr_uarts = no;
      }
      然后arch_initcall(s3c_arch_init);-> platform_add_devices(s3c24xx_uart_devs,
      nr_uarts);注册设备到
      platform_bus_type.
      2.console 设备初始化
      selected clock c0239b70 (pclk) quot 26, calc 115740
      [console_initcall(s3c24xx_serial_initconsole)->register_console->console.setup->s3c24xx_serial_console.setup(s3c24xx_serial_console_setup)->uart_set_options->s3c24xx_serial_set_termios->s3c24xx_serial_getclk]console
      [ttySAC1] enabled                            
      [console_initcall(s3c24xx_serial_initconsole)->register_console]
      先是根据内核命令行选择并配置一个uart的驱动:static int s3c24xx_serial_initconsole(void){
          struct s3c24xx_uart_info *info;
          struct platform_device *dev = s3c24xx_uart_devs[0]; /*上面已经初始化了*/
          ......
          } else if (strcmp(dev->name, "s3c2440-uart") == 0) {
              info = s3c2440_uart_inf_at;  /*根据设备名称(通过cpu设这的,见上面第一节分析*/
          }
          ........
          s3c24xx_serial_console.data = &s3c24xx_uart_drv; /*选择uart驱动: ttySACx,
      204,64-66*/
          s3c24xx_serial_init_ports(info);
          register_console(&s3c24xx_serial_console);
          return 0;
      }
      然后再根据命令行参数选择uart端口和波特率:
      void register_console(struct console *console) /*s3c24xx_serial_console*/
      {
          ......
          for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
                  i++) {
              if (strcmp(console_cmdline[i].name, console->name) != 0)
                  continue;
              if (console->index >= 0 &&
                  console->index != console_cmdline[i].index)
                  continue;
              if (console->index < 0)
                  console->index = console_cmdline[i].index;
              if (console->setup &&
                  console->setup(console, console_cmdline[i].options) != 0)
      /*options中存的是波特率*/
                  break;
              console->flags |= CON_ENABLED;
              console->index = console_cmdline[i].index; /*我们的选择是ttySAC1*/
              if (i == selected_console) {
                  console->flags |= CON_CONSDEV;
                  preferred_console = selected_console;
              }
              break;
          }
      .............
      }
      3.uart设备驱动初始化
      Serial: 8250/16550 driver $Revision: 1.90 $ 4 ports, IRQ sharing enabled [
      module_init(serial8250_init)]
      s3c2440-uart.0: s3c2410_serial0 at MMIO 0x50000000 (irq = 70) is a S3C2440

      s3c2440-uart.1: s3c2410_serial1 at MMIO 0x50004000 (irq = 73) is a S3C2440

      s3c2440-uart.2: s3c2410_serial2 at MMIO 0x50008000 (irq = 76) is a S3C2440

      上面三行信息就是uart初始化的信息,具体是在uart_report_port这个函数内打印的.但是通过什么路径确时费了番周折.串口初始化就是
      module_init(s3c24xx_serial_modinit)
      static int __init s3c24xx_serial_modinit(void)
      {
          int ret;
          ret = uart_register_driver(&s3c24xx_uart_drv); /*选择uart驱动: ttySACx,
      204,64-66,设备名称s3c2410_serial*/
          if (ret < 0) {
              printk(KERN_ERR "failed to register UART driver ");
              return -1;
          }
          s3c2400_serial_init();  /*这里有4个cpu的串口初始化函数,到底那个可以成功?*/
          s3c2410_serial_init();  /*这个在配置里选上了*/
          s3c2412_serial_init();
          s3c2440_serial_init();  /*这个也在配置里选上了*/
          return 0;
      }
      只从打印信息看,当然是选择了2440那个,下面从代码里找这个根据:
      static inline int s3c2410_serial_init(void)
      {
          return s3c24xx_serial_init(&s3c2410_serial_drv, &s3c2410_uart_inf);
      }
      static inline int s3c2440_serial_init(void)
      {
          return s3c24xx_serial_init(&s3c2440_serial_drv, &s3c2440_uart_inf);
      }
      static struct platform_driver s3c2410_serial_drv = {
          .probe        = s3c2410_serial_probe,
          .remove        = s3c24xx_serial_remove,
          .suspend    = s3c24xx_serial_suspend,
          .resume        = s3c24xx_serial_resume,
          .driver        = {
              .name    = "s3c2410-uart",
              .owner    = THIS_MODULE,
          },
      };
      static struct platform_driver s3c2440_serial_drv = {
          .probe        = s3c2440_serial_probe,
          .remove        = s3c24xx_serial_remove,
          .suspend    = s3c24xx_serial_suspend,
          .resume        = s3c24xx_serial_resume,
          .driver        = {
              .name    = "s3c2440-uart",
              .owner    = THIS_MODULE,
          },
      };
      上面两个初始化函数其实都是调用:
      static int s3c24xx_serial_init->
      int platform_driver_register(struct platform_driver *drv)
      {
          drv->driver.bus = &platform_bus_type;
          if (drv->probe)
              drv->driver.probe = platform_drv_probe;
          ......
          return driver_register(&drv->driver);
      }
      driver_register->bus_add_driver->
      int bus_add_driver(struct device_driver *drv)
      { 
          ......
          if (drv->bus->drivers_autoprobe) { /*默认是autoprobe*/
              error = driver_attach(drv);
              if (error)
                  goto out_unregister;
          }
        ......
      }
      driver_attach->bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);->
      static int __driver_attach(struct device * dev, void * data)
      {
          struct device_driver * drv = data;
          .......
          if (!dev->driver) /*这里就能找到在第一节中注册的uart dev*/
              driver_probe_device(drv, dev);
          }
          .....
      }
      int driver_probe_device(struct device_driver * drv, struct device * dev)
      {
          int ret = 0;
          if (drv->bus->match && !drv->bus->match(dev, drv))
              goto done;
          ret = really_probe(dev, drv); /* ->
      dev->bus->probe(dev)或者drv->probe(dev),这个bus没有probe*/
          ....
      }
      这里终于找到判定一个设备的驱动的条件:platform_bus_type
      ->platform_match->就是一个字符创的比较,看设备和驱动的名字是否一致:
      strncmp(pdev->name, drv->name, BUS_ID_SIZE)
      翻翻上面注册的名字,当然是2440的驱动胜出. 所以probe就调用了:
      s3c2440_serial_probe->uart_add_one_port->uart_report_port.
      4. uart设备注册后对console设备的影响(register_console只是早期注册给内核printk的)
      第二节谈到console的注册:
      static int s3c24xx_serial_initconsole(void)
      {
          struct platform_device *dev = s3c24xx_uart_devs[0]; /*上面已经初始化了*/
          ......
          s3c24xx_serial_console.data = &s3c24xx_uart_drv; /*选择uart驱动: ttySACx,
      204,64-66*/
          register_console(&s3c24xx_serial_console);
          return 0;
      }
      static struct console s3c24xx_serial_console =
      {
          .name        = S3C24XX_SERIAL_NAME,
          .device        = uart_console_device, /*找到此console对应的tty*/
          .flags        = CON_PRINTBUFFER,
          .index        = -1,
          .write        = s3c24xx_serial_console_write,
          .setup        = s3c24xx_serial_console_setup
          .data =  &s3c24xx_uart_drv;
      };
      static struct uart_driver s3c24xx_uart_drv = {
          .owner        = THIS_MODULE,
          .dev_name    = "s3c2410_serial",
          .nr        = 3,
          .cons        = S3C24XX_SERIAL_CONSOLE,
          .driver_name    = S3C24XX_SERIAL_NAME,
          .major        = S3C24XX_SERIAL_MAJOR,
          .minor        = S3C24XX_SERIAL_MINOR,
      };
      这个console只提供了最少的接口供printk使用.见register_console->release_console_sem.
      然后,在第三节谈到的uart设备初始化中:
      static int __init s3c24xx_serial_modinit(void)
      {
          int ret;
          ret = uart_register_driver(&s3c24xx_uart_drv);
      /*初始化s3c24xx_uart_drv->tty_driver*/
           /*初始化tty_driver后uart_console_device就能找到对应tty设备了*/
         ...
      }
      static inline int
      s3c2440_serial_init->s3c24xx_serial_init(&s3c2440_serial_drv,
      &s3c2440_uart_inf)-> __driver_attach ->...->really_probe内,将注册的uart
      platform_device设备进行进一步初始化:dev->driver =
      drv;要注意s3c2440_serial_drv是platform_driver,而不是uart_driver:s3c24xx_uart_drv().

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