如果我们添加一个不支持 PNP（即插即用）的设备，制造商有望提供有关如何为其分配 IRQ 值的明确指示。
但是，如果我们不知道要指定什么 IRQ 值，应该使用什么命令行来检查 IRQ 值是否空闲？
lsdev显示有关设备的信息：
$lsdev
Device DMA IRQ I/O Ports
------------------------------------------------
0000:00:02.0 7000-703f
0000:00:1f.2 7060-707f 7080-7087 7088-708f 7090-7093 7094-7097
0000:00:1f.3 efa0-efbf
0000:01:00.0 6000-607f
0000:04:00.0 4000-40ff
0000:05:00.0 3000-30ff
acpi 9
ACPI 1800-1803 1804-1805 1808-180b 1810-1815 1820-182f 1850-1850
ahci 43 7060-707f 7080-7087 7088-708f 7090-7093 7094-7097
cascade 4
这个 cmd 怎么样lsdev，足以完成这个任务吗？例如，如果我们想知道 1233 是否空闲，我们可以运行以下命令：
lsdev | awk '{print $3}'|grep 1233
笔记： $3使用上面的方法是因为 IRQ 值打印在输出的第三列中lsdev。
那么如果没有输出，就代表可以免费给我们使用了？
答案1
查看手册页，lsdev有这样的评论：
该程序仅显示内核对存在的硬件的想法，而不是实际物理上可用的硬件。
的输出lsdev实际上只是文件的内容/proc/interrupts：
摘自man proc
/proc/interrupts
This is used to record the number of interrupts per CPU per IO
device. Since Linux 2.6.24, for the i386 and x86_64 architectures,
at least, this also includes interrupts internal to the system (that
is, not associated with a device as such), such as NMI (non‐
maskable interrupt), LOC (local timer interrupt), and for SMP
systems, TLB (TLB flush interrupt), RES (rescheduling interrupt),
CAL (remote function call interrupt), and possibly others. Very
easy to read formatting, done in ASCII.
所以我可能会放弃以下内容/proc/interrupts：
$ cat /proc/interrupts
CPU0 CPU1 CPU2 CPU3
0: 157 0 0 0 IO-APIC-edge timer
1: 114046 13823 22163 22418 IO-APIC-edge i8042
8: 0 0 0 1 IO-APIC-edge rtc0
9: 863103 151734 155913 156348 IO-APIC-fasteoi acpi
12: 2401994 396391 512623 477252 IO-APIC-edge i8042
16: 555 593 598 626 IO-APIC-fasteoi mmc0
19: 127 31 83 71 IO-APIC-fasteoi ehci_hcd:usb2, firewire_ohci, ips
23: 32 8 21 16 IO-APIC-fasteoi ehci_hcd:usb1, i801_smbus
40: 5467 4735 1518263 1230227 PCI-MSI-edge ahci
41: 1206772 1363618 2193180 1477903 PCI-MSI-edge i915
42: 267 5142231 817 590 PCI-MSI-edge iwlwifi
43: 5 8 6 4 PCI-MSI-edge mei_me
44: 0 2 2 23405 PCI-MSI-edge em1
45: 19 66 39 23 PCI-MSI-edge snd_hda_intel
NMI: 12126 25353 28874 26600 Non-maskable interrupts
LOC: 29927091 27300830 30247245 26674337 Local timer interrupts
SPU: 0 0 0 0 Spurious interrupts
PMI: 12126 25353 28874 26600 Performance monitoring interrupts
IWI: 634179 806528 600811 632305 IRQ work interrupts
RTR: 5 1 1 0 APIC ICR read retries
RES: 4083290 3763061 3806592 3539082 Rescheduling interrupts
CAL: 16375 624 25561 737 Function call interrupts
TLB: 806653 778539 828520 806776 TLB shootdowns
TRM: 0 0 0 0 Thermal event interrupts
THR: 0 0 0 0 Threshold APIC interrupts
MCE: 0 0 0 0 Machine check exceptions
MCP: 416 416 416 416 Machine check polls
ERR: 0
MIS: 0