通过sysfs 访问 PCI 设备资源

5. Accessing PCI device resources through sysfs — The Linux Kernel documentation

sysfs 通常挂在到/sys 目录，提供了平台对于 PCI 资源的访问，一个服务器上的 PCI 长这个样子，路径里的10000:01:00.0就是 pci 设备的地址。

[root@TENCENT64 ~]# ll /sys/bus/pci/devices/10000:01:00.0/
total 0
-r--r--r-- 1 root root  4096 May 20 19:26 aer_dev_correctable
-r--r--r-- 1 root root  4096 May 20 19:26 aer_dev_fatal
-r--r--r-- 1 root root  4096 May 20 19:26 aer_dev_nonfatal
-r--r--r-- 1 root root  4096 May 20 19:26 ari_enabled
-rw-r--r-- 1 root root  4096 May 20 19:26 broken_parity_status
-r--r--r-- 1 root root  4096 May 11 16:06 class
-rw-r--r-- 1 root root  4096 May 11 16:06 config
-r--r--r-- 1 root root  4096 May 20 19:26 consistent_dma_mask_bits
-r--r--r-- 1 root root  4096 May 20 19:26 current_link_speed
-r--r--r-- 1 root root  4096 May 20 19:26 current_link_width
-rw-r--r-- 1 root root  4096 May 20 19:26 d3cold_allowed
-r--r--r-- 1 root root  4096 May 11 16:06 device
-r--r--r-- 1 root root  4096 May 20 19:26 dma_mask_bits
lrwxrwxrwx 1 root root     0 May 12 02:04 driver -> ../../../../../../bus/pci/drivers/nvme
-rw-r--r-- 1 root root  4096 May 20 19:26 driver_override
-rw-r--r-- 1 root root  4096 May 20 19:26 enable
-r--r--r-- 1 root root  4096 May 11 16:06 irq
-r--r--r-- 1 root root  4096 May 20 19:26 local_cpulist
-r--r--r-- 1 root root  4096 May 20 19:26 local_cpus
-r--r--r-- 1 root root  4096 May 20 19:26 max_link_speed
-r--r--r-- 1 root root  4096 May 20 19:26 max_link_width
-r--r--r-- 1 root root  4096 May 12 02:04 modalias
-rw-r--r-- 1 root root  4096 May 20 19:26 msi_bus
drwxr-xr-x 2 root root     0 May 20 19:26 msi_irqs
-rw-r--r-- 1 root root  4096 May 12 02:04 numa_node
drwxr-xr-x 3 root root     0 May 11 16:11 nvme
-r--r--r-- 1 root root  4096 May 20 19:26 pools
drwxr-xr-x 2 root root     0 May 20 19:26 power
--w--w---- 1 root root  4096 May 20 19:26 remove
--w------- 1 root root  4096 May 20 19:26 rescan
--w------- 1 root root  4096 May 20 19:26 reset
-r--r--r-- 1 root root  4096 May 11 16:06 resource
-rw------- 1 root root 32768 May 20 14:48 resource0
-r--r--r-- 1 root root  4096 May 20 19:26 revision
-rw------- 1 root root 65536 May 20 19:26 rom
-rw-r--r-- 1 root root  4096 May 20 19:26 sriov_drivers_autoprobe
-rw-r--r-- 1 root root  4096 May 20 19:26 sriov_numvfs
-r--r--r-- 1 root root  4096 May 20 19:26 sriov_offset
-r--r--r-- 1 root root  4096 May 20 19:26 sriov_stride
-r--r--r-- 1 root root  4096 May 20 19:26 sriov_totalvfs
-r--r--r-- 1 root root  4096 May 20 19:26 sriov_vf_device
lrwxrwxrwx 1 root root     0 May 11 16:45 subsystem -> ../../../../../../bus/pci
-r--r--r-- 1 root root  4096 May 20 19:26 subsystem_device
-r--r--r-- 1 root root  4096 May 20 19:26 subsystem_vendor
-rw-r--r-- 1 root root  4096 May 20 19:26 uevent
-r--r--r-- 1 root root  4096 May 11 16:06 vendor

目录里面的每个文件都对应他们自己的 function

file	function
class	PCI class (ascii, ro)
config	PCI config space (binary, rw)
device	PCI device (ascii, ro)
enable	Whether the device is enabled (ascii, rw)
irq	IRQ number (ascii, ro)
local_cpus	nearby CPU mask (cpumask, ro)
remove	remove device from kernel’s list (ascii, wo)
resource	PCI resource host addresses (ascii, ro)
resource0..N	PCI resource N, if present (binary, mmap, rw1)
resource0_wc..N_wc	PCI WC map resource N, if prefetchable (binary, mmap)
revision	PCI revision (ascii, ro)
rom	PCI ROM resource, if present (binary, ro)
subsystem_device	PCI subsystem device (ascii, ro)
subsystem_vendor	PCI subsystem vendor (ascii, ro)
vendor	PCI vendor (ascii, ro)

ro - read only file
rw - file is readable and writable
wo - write only file
mmap - file is mmapable
ascii - file contains ascii text
binary - file contains binary data
cpumask - file contains a cpumask type