Re: [Xenomai] x86 MSI support

[Philippe Gerum <rpm@xenomai.org>]

On 06/15/2012 08:44 PM, Jeff Weber wrote:
> Is the FAQ line:
>
> "The I-pipe patch currently does not support MSI interrupts."
>
> still true?  This FAQ is dated to 2008.
>

In retrospect, this FAQ entry is somewhat misleading. As Jan pointed out 
a couple of times already, the I-pipe does handle MSI interrupts 
properly, but doesn't allow non-root domains to call the IRQ 
masking/unmasking code for MSI. Since unmasking is usually paired with 
requesting an IRQ, and masking is paired with releasing it, the 
restriction should include the request/free calls as well.

There is no reason to mask MSI in the pre-handling code due to their 
semantics, and therefore no reason to unmask them upon return from the 
handler, so the restriction turns out to be a non-issue for most use 
cases. If a primary domain handler really wants to prevent more MSI to 
come from a given source, then it should quiesce the issuing device.

> I've been using MSIs and adeos-ipipe-2.6.38.8-x86-2.10-01.patch and haven't
> seen a problem yet.
>

-- 
Philippe.