Hi folks, I'm trying to write an input device driver basicaly to play with interrupt handlers. The idea at first was to catch all keys pressed on my keyboard, nothing else, but some doubts rised after I wrote the driver and it didn't work out. The code so far is as follows: https://gist.github.com/bmeneguele/621d4bbbfa28fca200df6ba289cfb3fc Now the questions: 1) from /proc/interrupts I saw the i8042 keyboard+mouse controller on IRQ line 1 and 12: CPU0 CPU1 CPU2 CPU3 0: 55 0 0 0 IR-IO-APIC 2-edge timer 1: 101 5 7 2 IR-IO-APIC 1-edge i8042 8: 0 0 0 1 IR-IO-APIC 8-edge rtc0 9: 7216 3565 16517 3485 IR-IO-APIC 9-fasteoi acpi 12: 212 29 323 51 IR-IO-APIC 12-edge i8042 16: 0 0 0 0 IR-IO-APIC 16-fasteoi i801_smbus 19: 15 0 6 3 IR-IO-APIC 19-fasteoi [...] then I thought I could share the line along with it, once in drivers/input/serio/i8042.c the request_irq() is being called with IRQF_SHARED. Is there a problem here? 2) I'm using a USB keyboard as the testing device, and TBH I got confused if I could actually use the input subsystem for that or I _should_ use HID instead (considering the keyboard is HID compliant). 3) the output I'm receiving is just one message regardless the number of keys I press: [... (make && insmod) ...] $ dmesg | tail [75013.625311] input: Bmeneg's Keyboard as /devices/virtual/input/input25 [75056.682676] [my_kbd] kbd_irq_handler:22:: irq 12 occured! [... (rmmod && make && insmod) ...] [75132.203324] input: Bmeneg's Keyboard as /devices/virtual/input/input26 [75149.669112] [my_kbd] kbd_irq_handler:22:: irq 1 occured! [... (rmmod && make && insmod) ...] [75164.213562] input: Bmeneg's Keyboard as /devices/virtual/input/input27 [75168.720791] [my_kbd] kbd_irq_handler:22:: irq 1 occured! [... (rmmod && make && insmod) ...] [75390.584746] input: Bmeneg's Keyboard as /devices/virtual/input/input28 [75397.149047] [my_kbd] kbd_exit:73:: irq reference counter: 1 [... (rmmod && make && insmod) ...] [79146.583034] input: Bmeneg's Keyboard as /devices/virtual/input/input29 [79159.647871] [my_kbd] kbd_exit:73:: irq reference counter: 1 as you can see I tried with prints inside IRQ handler, that I changed to a ref counter considering a previous knowledge from embedded systems that prints inside IRQs are bad :D (is it still true for linux kernel?), and the output from prints (inside IRQs) just appears after I `rmmod` the driver. Of course something is wrong in my code, but what? (handle kbd as input device? IRQ shared with i8042? wrong way to handle IRQ?) Well, this is my first time trying to accomplish something using real hardware in kernel space, not using just tutorial copy/paste or software-only things like timers. Because of that any info would be really great. What I'm trying to get here is just dive into bottom-helves execution (work queues) to understand how they actually works and of course more advanced things later! Thanks in advance! Note: using kernel 4.12.12 here. -- bmeneg PGP Key: http://bmeneg.com/pubkey.txt