Re: MSI messages

Manu Abraham
2008-12-14T11:15:38Z

Grant Grundler wrote:
> On Sat, Dec 13, 2008 at 01:38:24PM +0400, Manu Abraham wrote:
>> Hi,
>>
>> I am wondering how to handle this:
>>
>> Does the kernel somehow handle MSI message readback from the PCI config space
>> for the MSI message as described in 6.8.1 of the PCI Bus specification 2.3 or
>> does a device specific driver have to read the Message Address and Data ?
>>
>> To put it short: i am wondering how i should read the MSI messages.
>
> The "message" is actually mapped to an the interrupt vector by the core
> generic interrupt handling code in the kernel.
>
> A "GSI" (Generic Sys Interrupt?) is associated with each entry in
> the MSI-X table. Driver then calls request_irq() to bind an interrupt
> handler to each GSI. So the driver never directly sees the "message".

Oh, you mean the array of irq_handlers in the MSI-X table should
correspond to a particular message ?

I remember sometime back somebody stated that one might not get
the requested number of handlers what you requested.

In such a case, if the irq_handlers are mapped in a static fashion, one
might not get any interrupt callbacks for a specific functionality of
the hardware. Or is there something missing in what i understood ?

Regards,
Manu