[SOLVED] Cannot register interrupt for a PCI shared interrupt line

Issue

Good night,

I am trying to code some simple linux module that registers an existent shared IRQ line.

By looking at /proc/interrupts, I can see that the line I want to use has the irq_no=17.

For reference here is the output. As we can see the b43 driver module has already registered on the line, but the flags in the linux kernel code indicate that it is a shared line.

           CPU0       CPU1 
  0:     334476     345390   IO-APIC-edge      timer
  1:         28         26   IO-APIC-edge      i8042
  8:          0          1   IO-APIC-edge      rtc0
  9:          0          1   IO-APIC-fasteoi   acpi
 12:       1623        153   IO-APIC-edge      i8042
 14:          0          0   IO-APIC-edge      ata_piix
 15:          0          0   IO-APIC-edge      ata_piix
 16:        152        129   IO-APIC-fasteoi   nouveau
 17:      46543      40167   IO-APIC-fasteoi   b43
 18:       6129       5015   IO-APIC-fasteoi   ata_piix
 19:         48         28   IO-APIC-fasteoi   firewire_ohci, yenta
 20:          1          1   IO-APIC-fasteoi   ehci_hcd:usb2, uhci_hcd:usb3, uhci_hcd:usb5
 21:          0          0   IO-APIC-fasteoi   uhci_hcd:usb4, uhci_hcd:usb6
 22:         47         34   IO-APIC-fasteoi   ehci_hcd:usb1, uhci_hcd:usb7
 44:        129        138   PCI-MSI-edge      hda_intel
 45:          2          1   PCI-MSI-edge      eth0
NMI:          0          0   Non-maskable interrupts
LOC:     227794     229233   Local timer interrupts
SPU:          0          0   Spurious interrupts
PMI:          0          0   Performance monitoring interrupts
IWI:          0          0   IRQ work interrupts
RES:     244428     258417   Rescheduling interrupts
CAL:        340        462   Function call interrupts
TLB:       1056        916   TLB shootdowns
TRM:          0          0   Thermal event interrupts
THR:          0          0   Threshold APIC interrupts
MCE:          0          0   Machine check exceptions
MCP:         15         15   Machine check polls
ERR:          0
MIS:          0

I am trying to do the following:

static int __init ptdk_init(void)
{
     printk(KERN_INFO  "starting the kernel listener to the firmware module.\n"); 
     ptdk_could_not_register = request_threaded_irq(17, (irq_handler_t) ptdk_irq_handler,
                (irq_handler_t) ptdk_threaded_irq_handler, IRQF_SHARED, "ptdk", dummy);
     if (ptdk_could_not_register != 0) {
         printk(KERN_INFO "Could not request an irq for 17. %d", ptdk_could_not_register);
     }
     return 0;
 }

The dummy is a simple dev_id in order to register a cookie so the shared interrupt can free the line with context. (It is required a unique id to request a shared IRQ).

It just follows the following structure:

typedef struct{
    int i;
} ptdk_dummy_device;

So this should in principle work. But when trying to register the IRQ it returns -22 which is -EINVAL.

Am I missing something important? No other guide seems to give me any solutions. Thank you for your time and patience.

Solution

I was able to solve this as I was trying to make the cookie ID not a valid pointer.

Working code:

     ptdk_could_not_register = request_threaded_irq(17, (irq_handler_t) ptdk_irq_handler,
            (irq_handler_t) ptdk_threaded_irq_handler, IRQF_SHARED, "ptdk", &dummy);

Please, see the now &dummy.

Answered By - as43z

Answer Checked By - Marilyn (WPSolving Volunteer)