linux-kernel - Re: [PATCH v3 1/3] resource: Add @flags to region

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Message-ID: <CA+55aFy4WQrWexC4u2LxX9Mw2NVoznw7p3Yh=iF4Xtf7zKWnRw@mail.gmail.com>
Date:	Thu, 3 Dec 2015 11:01:08 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Toshi Kani <toshi.kani@....com>,
	Dan Williams <dan.j.williams@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Tony Luck <tony.luck@...el.com>,
	Vishal L Verma <vishal.l.verma@...el.com>,
	Linux MM <linux-mm@...ck.org>,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	Linux ACPI <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/3] resource: Add @flags to region_intersects()

On Thu, Dec 3, 2015 at 10:40 AM, Borislav Petkov <bp@...en8.de> wrote:
> On Thu, Dec 03, 2015 at 11:54:19AM -0700, Toshi Kani wrote:
>> Adding a new type for regular memory will require inspecting the codes
>> using IORESOURCE_MEM currently, and modify them to use the new type if
>> their target ranges are regular memory.  There are many references to this
>> type across multiple architectures and drivers, which make this inspection
>> and testing challenging.
>
> What's wrong with adding a new type_flags to struct resource and not
> touching IORESOURCE_* at all?

Bah. Both of these ideas are bogus.

Just add a new flag. The bits are already modifiers that you can
*combine* to show what kind of resource it is, and we already have
things like IORESOURCE_PREFETCH etc, that are in *addition* to the
normal IORESOURCE_MEM bit.

Just add another modifier: IORESOURCE_RAM.

So it would still show up as IORESOURCE_MEM, but it would have
additional information specifying that it's actually RAM.

If somebody does something like

     if (res->flags == IORESOURCE_MEM)

then they are already completely broken and won't work *anyway*. It's
a bitmask, bit a set of values.

             Linus
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