On Wed, Sep 07, 2011 at 12:39:09PM +0800, Wen Congyang wrote:
> At 09/06/2011 03:45 PM, Avi Kivity Write:
> > On 09/06/2011 06:06 AM, Wen Congyang wrote:
> >> > Use the uio driver -
> >> > http://docs.blackfin.uclinux.org/kernel/generated/uio-howto/. You
> >> just
> >> > mmap() the BAR from userspace and play with it.
> >>
> >> When I try to bind ivshmem to uio_pci_generic, I get the following
> >> messages:
> >> uio_pci_generic 0000:01:01.0: No IRQ assigned to device: no support
> >> for interrupts?
> >>
> >
> > No idea what this means.
>
> PCI 3.0 6.2.4
> For x86 based PCs, the values in this register correspond to IRQ numbers
> (0-15) of the standard dual
> 8259 configuration. The value 255 is defined as meaning "unknown" or "no
> connection" to the interrupt
> controller. Values between 15 and 254 are reserved.
>
> The register is interrupt line.
>
> I read the config of this device, the interrupt line is 0. It means that it
> uses the IRQ0.
>
> The following is the uio_pci_generic's code:
> static int __devinit probe(struct pci_dev *pdev,
> const struct pci_device_id *id)
> {
> struct uio_pci_generic_dev *gdev;
> int err;
>
> err = pci_enable_device(pdev);
> if (err) {
> dev_err(&pdev->dev, "%s: pci_enable_device failed: %d\n",
> __func__, err);
> return err;
> }
>
> if (!pdev->irq) {
> dev_warn(&pdev->dev, "No IRQ assigned to device: "
> "no support for interrupts?\n");
> pci_disable_device(pdev);
> return -ENODEV;
> }
> ...
> }
>
> This function will be called when we write 'domain:bus:slot.function' to
> /sys/bus/pci/drivers/uio_pci_generic/bind.
> pdev->irq is 0, it means the device uses IRQ0. But we refuse it. I do not why.
>
> To Michael S. Tsirkin
> This code is writen by you. Do you know why you check whether pdev->irq is 0?
>
> Thanks
> Wen Congyang
>
> >
Well I see this in linux:
/*
* Read interrupt line and base address registers.
* The architecture-dependent code can tweak these, of course.
*/
static void pci_read_irq(struct pci_dev *dev)
{
unsigned char irq;
pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &irq);
dev->pin = irq;
if (irq)
pci_read_config_byte(dev, PCI_INTERRUPT_LINE, &irq);
dev->irq = irq;
}
Thus a device without an interrupt pin will get irq set to 0,
and this seems the right way to detect such devices.
I don't think PCI devices really use IRQ0 in practice,
its probably used for PC things. More likely the system is
misconfigured. Try lspci -vv to see what went wrong.
--
MST
