目的：
1. 为我们自己的watchdog写一个驱动
步骤：
通过之前的介绍，我们很容易猜想到写我们基于PCI的watchdog驱动，可以分2个步骤。
1. 探测加载PCI设备
这部分代码跟我们的设备本身没有任何关系。
我们通过这部分代码，找到 厂商ID为 0x1af4， 设备ID为0x0101的设备。这个设备是我们用qemu中定义我们的watchdog中指定的。
#define PCI_VENDOR_ID_REDHAT 0x1af4
#define PCI_DEVICE_ID_CWD 0x0101
很自然的可以先到我们需要一个probe的函数来探测PCI设备。 事实确实如此。
我们通过一个pci_driver定义这部分。
static struct pci_driver cwd_driver = {
.name = ESB_MODULE_NAME,
.id_table = cwd_pci_tbl,
.probe = cwd_probe,
.remove = cwd_remove,
.shutdown = cwd_shutdown,
};
我们可以直接参考一下其他的PCI设备驱代码来实现这部分代码，比如： drivers/watchdog/i6300esb.c
代码如下。
cwd_demo.c
![[虚拟化/云][全栈demo] 为qemu增加一个PCI的watchdog外设（六）第1张](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
![[虚拟化/云][全栈demo] 为qemu增加一个PCI的watchdog外设（六）第2张](https://images.cnblogs.com/OutliningIndicators/ExpandedBlockStart.gif)
1 #include <linux/init.h> //初始换函数 2 #include <linux/kernel.h> //内核头文件 3 #include <linux/module.h> //模块的头文件 4 #include <linux/pci.h> 5 #include <linux/miscdevice.h> 6 #include <linux/types.h> 7 #include <linux/fs.h> 8 #include <linux/mm.h> 9 #include <linux/watchdog.h> 10 #include <linux/ioport.h> 11 #include <linux/uaccess.h> 12 #include <linux/io.h> 13 14 15 16 #define ESB_MODULE_NAME "cstl watchdog" 17 18 /* We only use 1 card for cwd_demo */ 19 static int cards_found; 20 static struct pci_dev *cwd_pci; 21 22 MODULE_LICENSE("GPL"); 23 24 #define CWD_VERSION "0.1" 25 #define PCI_VENDOR_ID_REDHAT 0x1af4 26 #define PCI_DEVICE_ID_CWD 0x0101 27 /* internal variables */ 28 static void __iomem *BASEADDR; 29 30 31 /* 32 * Data for PCI driver interface 33 */ 34 static DEFINE_PCI_DEVICE_TABLE(cwd_pci_tbl) = { 35 { PCI_DEVICE(PCI_VENDOR_ID_REDHAT, PCI_DEVICE_ID_CWD), }, 36 { 0, }, /* End of list */ 37 }; 38 MODULE_DEVICE_TABLE(pci, cwd_pci_tbl); 39 40 41 static unsigned char cwd_getdevice(struct pci_dev *pdev) 42 { 43 if (pci_enable_device(pdev)) { 44 printk(KERN_ERR "failed to enable device "); 45 goto err_devput; 46 } 47 48 if (pci_request_region(pdev, 0, ESB_MODULE_NAME)) { 49 printk(KERN_ERR "failed to request region "); 50 goto err_disable; 51 } 52 53 BASEADDR = pci_ioremap_bar(pdev, 0); 54 if (BASEADDR == NULL) { 55 /* Something's wrong here, BASEADDR has to be set */ 56 printk(KERN_ERR "failed to get BASEADDR "); 57 goto err_release; 58 } 59 60 /* Done */ 61 cwd_pci = pdev; 62 return 1; 63 64 err_release: 65 pci_release_region(pdev, 0); 66 err_disable: 67 pci_disable_device(pdev); 68 err_devput: 69 return 0; 70 } 71 72 73 static int cwd_probe(struct pci_dev *pdev, 74 const struct pci_device_id *ent) 75 { 76 int ret; 77 78 cards_found++; 79 if (cards_found == 1) 80 printk(KERN_INFO "Cstl WatchDog Timer Driver v%s ", 81 CWD_VERSION); 82 83 if (cards_found > 1) { 84 printk(KERN_ERR "Cstl driver only supports 1 device "); 85 return -ENODEV; 86 } 87 88 /* Check whether or not the hardware watchdog is there */ 89 if (!cwd_getdevice(pdev) || cwd_pci == NULL) 90 return -ENODEV; 91 return 0; 92 } 93 94 static int cwd_timer_stop(void) 95 { 96 /* Returns 0 if the timer was disabled, non-zero otherwise */ 97 return 0; 98 } 99 static void cwd_remove(struct pci_dev *pdev) 100 { 101 /* Stop the timer before we leave */ 102 cwd_timer_stop(); 103 104 /* Deregister */ 105 // misc_deregister(&cwd_miscdev); 106 iounmap(BASEADDR); 107 pci_release_region(cwd_pci, 0); 108 pci_disable_device(cwd_pci); 109 cwd_pci = NULL; 110 } 111 112 static void cwd_shutdown(struct pci_dev *pdev) 113 { 114 cwd_timer_stop(); 115 } 116 117 118 static struct pci_driver cwd_driver = { 119 .name = ESB_MODULE_NAME, 120 .id_table = cwd_pci_tbl, 121 .probe = cwd_probe, 122 .remove = cwd_remove, 123 .shutdown = cwd_shutdown, 124 }; 125 126 static int __init cwd_demo_start(void) 127 { 128 printk(KERN_ALERT "Loading cwd_demo module... "); 129 printk(KERN_ALERT "Hello, I'm cwd_demo "); 130 return pci_register_driver(&cwd_driver); 131 } 132 133 static void __exit cwd_demo_end(void) 134 { 135 pci_unregister_driver(&cwd_driver); 136 printk(KERN_ALERT "cwd demo Module Unloaded, Goodbye! "); 137 138 } 139 140 module_init(cwd_demo_start); 141 module_exit(cwd_demo_end);
Makefile
1 ifeq ($(KERNELRELEASE),) 2 KVERSION = $(shell uname -r) 3 all: 4 make -C /lib/modules/$(KVERSION)/build M=$(shell pwd) modules 5 echo $(shell pwd) 6 clean: 7 make -C /lib/modules/$(KVERSION)/build M=$(shell pwd) clean 8 else 9 obj-m :=cwd_demo.o 10 endif
编译加载：
$ make
$ sudo insmod cwd_demo.ko
查看加载结果：
发现加载失败
$ tail -n 40 -f /var/log/syslog
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759632] Hello, I'm cwd_demo
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759666] Cstl WatchDog Timer Driver v0.1
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759740] ------------[ cut here ]------------
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759749] WARNING: CPU: 0 PID: 15113 at /build/buil
dd/linux-lts-saucy-3.11.0/drivers/pci/pci.c:130 pci_ioremap_bar+0x71/0x80()
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759750] Modules linked in: cwd_demo(OF+) btrfs ra
id6_pq zlib_deflate xor ufs qnx4 hfsplus hfs minix ntfs msdos jfs xfs reiserfs ext2 usblp hello(POF)
rfcomm bnep bluetooth cirrus ttm drm_kms_helper drm sysimgblt sysfillrect syscopyarea ppdev mac_hid p
arport_pc i2c_piix4 psmouse serio_raw lp parport floppy [last unloaded: cwd_demo]
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759775] CPU: 0 PID: 15113 Comm: insmod Tainted: P
F W O 3.11.0-15-generic #25~precise1-Ubuntu
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759777] Hardware name: QEMU Standard PC (i440FX +
PIIX, 1996), BIOS Bochs 01/01/2011
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759778] 0000000000000082 ffff8800367b5b38 ffffff
ff8173bc5e 0000000000000007
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759781] 0000000000000000 ffff8800367b5b78 ffffff
ff810653ac ffff88003dba1098
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759783] ffff88003dba1000 ffff8800367b5c20 ffffff
ffa01e0000 ffff88003dba1098
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759785] Call Trace:
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759792] [<ffffffff8173bc5e>] dump_stack+0x46/0x58
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759797] [<ffffffff810653ac>] warn_slowpath_common+0x8c/0xc0
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759799] [<ffffffff810653fa>] warn_slowpath_null+0x1a/0x20
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759801] [<ffffffff813aaf91>] pci_ioremap_bar+0x71/0x80
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759805] [<ffffffffa01de12f>] cwd_probe+0x6f/0x1d0 [cwd_demo]
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759808] [<ffffffff813acd2b>] local_pci_probe+0x4b/0x80
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759810] [<ffffffff813ae5a9>] __pci_device_probe+0xd9/0xe0
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759813] [<ffffffff813ae5ea>] pci_device_probe+0x3a/0x60
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759817] [<ffffffff814948bc>] really_probe+0x6c/0x330
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759819] [<ffffffff81494d07>] driver_probe_device+0x47/0xa0
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759821] [<ffffffff81494e0b>] __driver_attach+0xab/0xb0
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759823] [<ffffffff81494d60>] ? driver_probe_device+0xa0/0xa0
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759825] [<ffffffff81492aee>] bus_for_each_dev+0x5e/0x90
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759827] [<ffffffff8149447e>] driver_attach+0x1e/0x20
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759829] [<ffffffff81493f0c>] bus_add_driver+0x10c/0x290
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759831] [<ffffffff8149538d>] driver_register+0x7d/0x160
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759834] [<ffffffffa0032000>] ? 0xffffffffa0031fff
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759836] [<ffffffff813ad56c>] __pci_register_driver+0x4c/0x50
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759838] [<ffffffffa003203a>] cwd_demo_start+0x3a/0x1000 [cwd_demo]
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759842] [<ffffffff8100212a>] do_one_initcall+0xfa/0x1b0
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759846] [<ffffffff810578e3>] ? set_memory_nx+0x43/0x50
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759852] [<ffffffff81730257>] do_init_module+0x80/0x1d1
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759857] [<ffffffff810d1af9>] load_module+0x4c9/0x5f0
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759859] [<ffffffff810cf270>] ? show_initstate+0x50/0x50
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759862] [<ffffffff810d1cd4>] SyS_init_module+0xb4/0x100
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759866] [<ffffffff8175099d>] system_call_fastpath+0x1a/0x1f
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759868] ---[ end trace 4d45fe543fa54a73 ]---
Jun 30 15:14:30 fsh-virtual-machine kernel: [612625.759869] failed to get BASEADDR
分析错误：
通过内核栈信息，我们知道，代码在调用 pci_ioremap_bar 出现了问题。
我们之前已经了解到，对PCI设备IO的操作，有两种方式，一种，是IO空间，一种是内存空间。我们这里抄袭了i6300esb的代码，esb采用的是内存空间。
很容易的想到，我们的外设是不支持内存空间的。
查看我们的qemu的代码，发现我们确实没有实现相关的代码。
这个可以通过我们的qemu monitor的 info qtree 来查看。
dev: cstl-watchdog, id ""
expiration-ticks = 10 (0xa)
addr = 05.0
romfile = ""
rombar = 1 (0x1)
multifunction = false
command_serr_enable = true
class Class 0880, addr 00:05.0, pci id 1af4:0101 (sub 1af4:1100)
bar 0: i/o at 0xc090 [0xc09f]
果真是不支持内存空间。
其实在PCI的spec文件中，有说明，如果从baro～bar5寄存器中读出来的地址是奇数，表示这是个IO空间，这是的地址要与～0x03UL做与运算，如果是偶数，则表示是内存空间。
/* here we are testing it is a io space or mem space */
unsigned int addr = 0;
pci_read_config_dword(pdev, 0x10, &addr);
printk(KERN_ERR "get BASEADDR: 0x%x ", addr);
在我们的log中将会输出以下的结果：
Jun 30 16:14:30 fsh-virtual-machine kernel: [612625.759872] failed to get get BASEADDR: 0xc91