Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1168286

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

Show key headers only | View raw

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
--
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 — Previous 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