Re: [PATCH] PCI: Only enable IO window if supported

From	Bjorn Helgaas <bhelgaas@google.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] PCI: Only enable IO window if supported
Date	2015-06-18 22:00 +0200
Message-ID	<pCO8H-1yB-15@gated-at.bofh.it> (permalink)
References	<pt5Xc-6re-1@gated-at.bofh.it> <puQKm-78Z-21@gated-at.bofh.it> <puVK1-61e-13@gated-at.bofh.it> <pv5q3-3FS-27@gated-at.bofh.it> <pCMqf-7Fz-43@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

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.

Bjorn
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

Re: [PATCH] PCI: Only enable IO window if supported Bjorn Helgaas <bhelgaas@google.com> - 2015-06-18 22:00 +0200
  Re: [PATCH] PCI: Only enable IO window if supported Guenter Roeck <linux@roeck-us.net> - 2015-06-18 23:00 +0200

csiph-web