[虚拟化/云][全栈demo] 为qemu增加一个PCI的watchdog外设（六）

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

#include <linux/init.h>  //初始换函数 
#include <linux/kernel.h>  //内核头文件 
#include <linux/module.h>  //模块的头文件 
#include <linux/pci.h> 
#include <linux/miscdevice.h> 
#include <linux/types.h> 
#include <linux/fs.h> 
#include <linux/mm.h> 
#include <linux/watchdog.h> 
#include <linux/ioport.h> 
#include <linux/uaccess.h> 
#include <linux/io.h> 
 
 
 
#define ESB_MODULE_NAME "cstl watchdog" 
 
/* We only use 1 card for cwd_demo */ 
static int cards_found; 
static struct pci_dev *cwd_pci; 
 
MODULE_LICENSE("GPL"); 
 
#define CWD_VERSION "0.1" 
#define PCI_VENDOR_ID_REDHAT 0x1af4 
#define PCI_DEVICE_ID_CWD 0x0101 
/* internal variables */ 
static void __iomem *BASEADDR; 
 
 
/*  
 * Data for PCI driver interface  
 */  
static DEFINE_PCI_DEVICE_TABLE(cwd_pci_tbl) = {  
        { PCI_DEVICE(PCI_VENDOR_ID_REDHAT, PCI_DEVICE_ID_CWD), },
        { 0, },                 /* End of list */
};
MODULE_DEVICE_TABLE(pci, cwd_pci_tbl);


static unsigned char cwd_getdevice(struct pci_dev *pdev)
{
        if (pci_enable_device(pdev)) {
                printk(KERN_ERR "failed to enable device
");
                goto err_devput;
        }

        if (pci_request_region(pdev, 0, ESB_MODULE_NAME)) {
                printk(KERN_ERR "failed to request region
");
                goto err_disable;
        }

        BASEADDR = pci_ioremap_bar(pdev, 0);
        if (BASEADDR == NULL) {
                /* Something's wrong here, BASEADDR has to be set */
                printk(KERN_ERR "failed to get BASEADDR
");
                goto err_release;
        }

        /* Done */
        cwd_pci = pdev;
        return 1;

err_release:
        pci_release_region(pdev, 0);
err_disable:
        pci_disable_device(pdev);
err_devput:
        return 0;
}


static int cwd_probe(struct pci_dev *pdev,
                const struct pci_device_id *ent)
{
        int ret;

        cards_found++;
        if (cards_found == 1)
                printk(KERN_INFO "Cstl WatchDog Timer Driver v%s
",
                        CWD_VERSION);

        if (cards_found > 1) {
                printk(KERN_ERR "Cstl driver only supports 1 device
");
                return -ENODEV;
        }

        /* Check whether or not the hardware watchdog is there */
        if (!cwd_getdevice(pdev) || cwd_pci == NULL)
                return -ENODEV;
        return 0;
}

static int cwd_timer_stop(void)
{
        /* Returns 0 if the timer was disabled, non-zero otherwise */
        return 0;
}
static void cwd_remove(struct pci_dev *pdev)
{
        /* Stop the timer before we leave */
        cwd_timer_stop();

        /* Deregister */
        // misc_deregister(&cwd_miscdev);
        iounmap(BASEADDR);
        pci_release_region(cwd_pci, 0);
        pci_disable_device(cwd_pci);
        cwd_pci = NULL;
}

static void cwd_shutdown(struct pci_dev *pdev)
{
        cwd_timer_stop();
}


static struct pci_driver cwd_driver = {
        .name           = ESB_MODULE_NAME,
        .id_table       = cwd_pci_tbl,
        .probe          = cwd_probe,
        .remove         = cwd_remove,
        .shutdown       = cwd_shutdown,
};

static int __init cwd_demo_start(void)
{
    printk(KERN_ALERT "Loading cwd_demo module...
");
    printk(KERN_ALERT "Hello, I'm cwd_demo
");
    return pci_register_driver(&cwd_driver);
}

static void __exit cwd_demo_end(void)
{
    pci_unregister_driver(&cwd_driver);
    printk(KERN_ALERT "cwd demo Module Unloaded, Goodbye!
");

}

module_init(cwd_demo_start);
module_exit(cwd_demo_end);

Makefile

ifeq ($(KERNELRELEASE),)
        KVERSION = $(shell uname -r)
all:
        make -C /lib/modules/$(KVERSION)/build M=$(shell pwd) modules
        echo $(shell pwd)
clean:
        make -C /lib/modules/$(KVERSION)/build M=$(shell pwd) clean
else
        obj-m :=cwd_demo.o
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