【65】如何通過sys文件系統remove和probe一個PCI設備

 \-[0000:00]+-01.4-[03]--+-00.0  Intel Corporation I350 Gigabit Network Connection
                   |                   \-00.1  Intel Corporation I350 Gigabit Network Connection

1、手動remove一個pci設備（bus:device.function 3:0.0和3.0.1）

echo 1 > /sys/bus/pci/devices/0000\:03\:00.0/remove 

echo 1 > /sys/bus/pci/devices/0000\:03\:00.1/remove

2、手動掃描pci設備

echo 1 > /sys/bus/pci/rescan 

當然如果想更精確一點，可以使用父設備下的recan來掃描子設備，兩者唯一的區別就是通過bus節點掃描會調用pci_find_next_bus把系統中的所有設備都rescan一遍。

echo 1 >/sys/bus/pci/devices/0000\:00\:01.4/rescan 

3、源碼到底是怎麼實現呢？

https://elixir.bootlin.com/linux/v5.3/source/drivers/pci/pci-sysfs.c     

 sys文件系統的函數裏面有3個節點device的remove、bus的rescan和devcie的rescan，當你往文件系統寫1時就回調attribute的store函數指針：

/* interface for exporting device attributes */
struct device_attribute {
	struct attribute	attr;
	ssize_t (*show)(struct device *dev, struct device_attribute *attr,
			char *buf);
	ssize_t (*store)(struct device *dev, struct device_attribute *attr,
			 const char *buf, size_t count);
};

remove主要是卸載資源和調用driver的remove 

下面是通過kprobe打印出來的remove調用棧

   <...>-4114  [059] .... 73835.573048: myprobe: (pci_remove_bus_device+0x0/0x100)
            bash-4114  [059] .... 73835.573066: <stack trace>
 => pci_remove_bus_device
 => pci_stop_and_remove_bus_device_locked
 => remove_store------------------入口
 => kernfs_fop_write
 => vfs_write
 => ksys_write
 => do_syscall_64
 => entry_SYSCALL_64_after_hwframe

rescan主要幹兩件事

（1）分配資源

（2）調用probe

kprobe打印的分配資源的調用棧
            bash-1596  [026] .... 56128.977294: myprobe: (pci_assign_resource+0x0/0x200)
            bash-1596  [026] .... 56128.977296: <stack trace>
 => pci_assign_resource
 => assign_requested_resources_sorted
 => __assign_resources_sorted
 => __pci_bus_assign_resources
 => __pci_bus_assign_resources
 => pci_assign_unassigned_bus_resources
 => pci_rescan_bus
 => rescan_store--------------------入口
 => kernfs_fop_write
 => vfs_write
 => ksys_write
 => do_syscall_64
 => entry_SYSCALL_64_after_hwframe

pci_assign_resource函數調用_pci_assign_resource分配設備需要的resource

分配完畢打印資源情況：pci_info(dev, "BAR %d: assigned %pR\n", resno, res);打印出就是下面的格式

具體實現原理見

https://blog.csdn.net/tiantao2012/article/details/68483118

[72131.692082] pci 0000:03:00.0: BAR 0: assigned [mem 0xef600000-0xef61ffff]
[72131.692087] pci 0000:03:00.1: BAR 0: assigned [mem 0xef620000-0xef63ffff]
[72131.692092] pci 0000:03:00.0: BAR 3: assigned [mem 0xef640000-0xef643fff]
[72131.692097] pci 0000:03:00.0: BAR 7: assigned [mem 0x323a0000000-0x323a001ffff 64bit pref]
[72131.692103] pci 0000:03:00.0: BAR 10: assigned [mem 0x323a0020000-0x323a003ffff 64bit pref]
[72131.692108] pci 0000:03:00.1: BAR 3: assigned [mem 0xef644000-0xef647fff]
[72131.692112] pci 0000:03:00.1: BAR 7: assigned [mem 0x323a0040000-0x323a005ffff 64bit pref]
[72131.692118] pci 0000:03:00.1: BAR 10: assigned [mem 0x323a0060000-0x323a007ffff 64bit pref]
[72131.692123] pci 0000:03:00.0: BAR 2: assigned [io  0x1000-0x101f]
[72131.692128] pci 0000:03:00.1: BAR 2: assigned [io  0x1020-0x103f]

 

     kworker/0:2-336   [000] ....  4201.787205: myprobe: (pci_enable_resources+0x0/0x170)
     kworker/0:2-336   [000] ....  4201.787228: <stack trace>
 => pci_enable_resources
 => pcibios_enable_device
 => do_pci_enable_device
 => pci_enable_device_flags
 => igb_probe
 => local_pci_probe
 => work_for_cpu_fn
 => process_one_work
 => worker_thread
 => kthread
 => ret_from_fork
     kworker/0:2-336   [000] ....  4201.825660: myprobe: (pci_enable_resources+0x0/0x170)
     kworker/0:2-336   [000] ....  4201.825671: <stack trace>
 => pci_enable_resources
 => pcibios_enable_device
 => do_pci_enable_device
 => pci_enable_device_flags
 => igb_probe
 => local_pci_probe
 => work_for_cpu_fn
 => process_one_work
 => worker_thread
 => kthread
 => ret_from_fork

起worker來調用driver probe。

            bash-4872  [026] .... 90924.365341: myprobe: (pci_device_probe+0x0/0x1c0)
            bash-4872  [026] .... 90924.365355: <stack trace>
 => pci_device_probe
 => really_probe
 => driver_probe_device
 => bus_for_each_drv
 => __device_attach
 => pci_bus_add_device
 => pci_bus_add_devices
 => pci_bus_add_devices
 => pci_rescan_bus
 => rescan_store--------------------入口
 => kernfs_fop_write
 => vfs_write
 => ksys_write
 => do_syscall_64
 => entry_SYSCALL_64_after_hwframe