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Date: Mon, 20 Sep 2010 22:40:56 +0200
From: Micha Nelissen <micha@neli.hopto.org>
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To: "Bounine, Alexandre" <Alexandre.Bounine@idt.com>
Subject: Re: [PATCH v2 03/10] RapidIO: Use stored ingress port number instead
	of register read
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Hi Alex,

Bounine, Alexandre wrote:
> struct rio_dev {
>     struct list_head global_list;
>     struct list_head net_list;
>     .....
>     ..... rest of rio_dev
>     .....
>     struct rio_switch switch[0];
> }

It makes sense to let rio_dev structures point to the switch they are 
attached to. That can be useful in various situations, but is not 
possible with this setup.

If a rio_dev is a switch then rdev->rswitch->rdev == rdev holds.

> This will remove extra memory allocation, remove overlapping structure
> members and clean code sections like one shown below:
> 
> 	u8 hopcount = 0xff;
> 	u16 destid = rdev->destid;
> 
> 	if (rdev->rswitch) {
> 		destid = rdev->rswitch->destid;
> 		hopcount = rdev->rswitch->hopcount;
> 	}    

Note that it is possible for rdev->destid to differ from 
rdev->rswitch->destid even if rswitch->rdev == rdev (for non-hosts i.e. 
agents). rswitch->destid is the destid by which we discovered the switch 
(and can reach it) but rdev->destid is the actual id given to the switch.

Micha