linux-kernel - Re: [PATCH 4/4] i2o: Use pci_bus_alloc_resource(), not allocate

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Message-ID: <CAErSpo7=vbbNck6Ua+-5ycHVCuby0OnxHMGmhSw3Qb-iXOsaeA@mail.gmail.com>
Date:	Wed, 26 Feb 2014 16:47:58 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
Cc:	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Markus Lidel <Markus.Lidel@...dowconnect.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] i2o: Use pci_bus_alloc_resource(), not
 allocate_resource() directly

On Wed, Feb 26, 2014 at 3:48 PM, One Thousand Gnomes
<gnomes@...rguk.ukuu.org.uk> wrote:
> On Wed, 26 Feb 2014 12:09:27 -0700
> Bjorn Helgaas <bhelgaas@...gle.com> wrote:
>
>> Convert i2o_res_alloc() to use pci_bus_alloc_resource() rather than
>> pci_find_parent_resource() and allocate_resource().  We don't have a
>> resource to start with, so pci_find_parent_resource() can't do anything
>> useful: a bus may have several memory resources available, so there might
>> be several possible parents.  This is more likely on root buses because
>> host bridges may have any number of apertures.
>>
>> I'm pretty sure this didn't work in the first place because it passed
>> size == min == max to allocate_resource().  The min and max parameters are
>> constraints on the *addresses* of the resource, not on its size, so I think
>> it was impossible for allocate_resource() to succeed.
>
> I don't think many i2o controllers ever used that path, and I doubt any
> in normal use did as the vision of offloading for devices on the host bus
> basically never happened (it happened even less than i2o)
>
> A rather more sensible question might be "If i2o went away is there
> anyone who would even notice". About the only devices that ever used i2o
> in the real world (AMI MegaRAID and some FC stuff) had native firmware or
> modes that worked better anyway.

I don't know anything about i2o, so I have no idea whether it could be
completely removed.  I just want to remove its usage of
pci_find_parent_resource() so I can change the semantics of that a bit
(see [1]).

Bjorn

[1] https://lkml.kernel.org/r/20140226193723.10125.15799.stgit@bhelgaas-glaptop.roam.corp.google.com
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