From: Guenter Roeck <linux@roeck-us.net>
To: Bjorn Helgaas <bhelgaas@google.com>
Cc: "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>,
Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH] PCI: Only enable IO window if supported
Date: Thu, 18 Jun 2015 13:53:23 -0700 [thread overview]
Message-ID: <20150618205323.GA527@roeck-us.net> (raw)
In-Reply-To: <CAErSpo5f4cf7cYZ1WxUQd7soEvNWCHowdNnHTbfGmKh16Vdsrg@mail.gmail.com>
On Thu, Jun 18, 2015 at 02:51:52PM -0500, Bjorn Helgaas wrote:
> On Thu, Jun 18, 2015 at 1:01 PM, Guenter Roeck <linux@roeck-us.net> wrote:
> > On Thu, May 28, 2015 at 07:41:12AM -0500, Bjorn Helgaas wrote:
> >>
> >> > > I'd like res->flags to reflect the capabilities of the hardware, not
> >> > > whether the window is currently enabled.
> >> > >
> >> > Flag bits seem to be all taken. Could we use IORESOURCE_DISABLED for that
> >> > purpose, or could that cause conflicts elsewhere ?
> >>
> >> Yes, I think IORESOURCE_DISABLED would be appropriate for any I/O windows
> >> below a host bridge that doesn't support I/O space.
> >>
> > I integrated Lorenzo's patch and tried to get this working.
> >
> > Problem is that the use of a resource is widely checked with "!res->flags"
> > throughout the code. That would have to be changed to something like
> > "(!res->flags || (res->flags & IORESOURCE_DISABLED))" whereever it is used.
> >
> > I tried going with "!res->flags" instead, but have not been able to get it
> > to work realiably; it is just very difficult to distinguish if "!res->flags"
> > means that the resource has not yet been assigned or if it means that it is not
> > supported.
> >
> > The correct approach, in my opinion, would be to go with IORESOURCE_DISABLED
> > and make the necessary changes whereever needed. Effectively this means to
> > replace the "!res->flags" check with something like pci_res_used() [ pick
> > your preferred name ] and define it as
> >
> > #define pci_res_used(res) ((res)->flags && !((res)->flags & IORESOURCE_DISABLED))
>
> I think that makes sense. Maybe "res_valid()"? It's not really
> PCI-specific, and "used" is a little ambiguous. So is "valid", I
> admit.
>
res_valid() sounds good to me. It is also nice and short.
Guenter
next prev parent reply other threads:[~2015-06-18 20:53 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-23 0:52 [PATCH] PCI: Only enable IO window if supported Guenter Roeck
2015-05-27 21:04 ` Bjorn Helgaas
2015-05-28 2:23 ` Guenter Roeck
2015-05-28 12:41 ` Bjorn Helgaas
2015-06-18 18:01 ` Guenter Roeck
2015-06-18 19:51 ` Bjorn Helgaas
2015-06-18 20:53 ` Guenter Roeck [this message]
2015-06-19 16:24 ` Lorenzo Pieralisi
2015-07-07 14:40 ` Lorenzo Pieralisi
2015-07-07 15:01 ` Guenter Roeck
2015-07-07 17:28 ` Lorenzo Pieralisi
2015-07-07 18:13 ` Guenter Roeck
2015-06-02 14:55 ` Lorenzo Pieralisi
2015-06-02 16:32 ` Bjorn Helgaas
2015-06-02 17:02 ` Guenter Roeck
2015-06-02 19:58 ` Bjorn Helgaas
2015-06-03 15:15 ` Guenter Roeck
2015-06-03 10:32 ` Lorenzo Pieralisi
2015-06-03 15:12 ` Guenter Roeck
2015-06-03 16:55 ` Lorenzo Pieralisi
2015-06-03 18:07 ` Guenter Roeck
2015-06-23 22:46 ` Benjamin Herrenschmidt
2015-06-23 23:02 ` Bjorn Helgaas
2015-06-23 23:14 ` Benjamin Herrenschmidt
2015-06-25 11:27 ` Lorenzo Pieralisi
2015-07-08 8:38 ` Lorenzo Pieralisi
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