From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Campbell <ian.campbell@citrix.com>
Subject: Re: [PATCH v4 05/17] xen/arm: ITS: implement
 hw_irq_controller for LPIs
Date: Mon, 20 Jul 2015 13:22:53 +0100
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To: Julien Grall <julien.grall@citrix.com>
Cc: Vijay Kilari <vijay.kilari@gmail.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Prasun Kapoor <Prasun.Kapoor@caviumnetworks.com>, Vijaya Kumar K <vijaya.kumar@caviumnetworks.com>, Tim Deegan <tim@xen.org>, "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>, Stefano Stabellini <stefano.stabellini@citrix.com>, manish.jaggi@caviumnetworks.com
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On Sat, 2015-07-18 at 11:13 +0100, Julien Grall wrote:
> Hi Ian,
> 
> On 15/07/2015 10:32, Ian Campbell wrote:
> >> and save 2 byte if not more with the alignment per irq_desc.
> >
> > If this is a concern then I would say we would either want a separate
> > array of per-pLPI information which we do not want in irq_desc because
> > it is irq specific, or do add a pointer to its_desc which points to an
> > array of per-event information.
> 
> I noticed that we have a field msi_desc in the structure irq_desc. On 
> ARM, the structure msi_desc is not defined at all but still waste a 8 
> byte for the pointer in the irq_desc.
> 
> Given that LPI is an MSI, I'm wondering if we could move all LPI related 
> data in this msi_desc. This would avoid to introduce new field in the 
> irq_desc structure.

Yes, I think I suggested something similar at some point, although I
seemed to think msi_desc was more similar to its_device.

Looking at the content of the struct, alloc_msi_entry and
msi_capability_init makes me less sure, it looks like msi_entry on x86
is allocated as an array (sized for events) stored per device, which
doesn't directly map onto how ARM is structured.

So I think you suggestion may make more sense.

> 
> The msi_desc would look like:
> 
> struct msi_desc
> {
> 	its_device *dev;
> 	unsigned int eventID;
> };
> 
> Regards,
>