linux-kernel - Re: [PATCH v2 2/7] kernel/resource: move and rename IORESOURCE_MEM_DRIVER

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Date:   Wed, 9 Sep 2020 09:16:46 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, linux-mm@...ck.org,
        linux-hyperv@...r.kernel.org, xen-devel@...ts.xenproject.org,
        linux-acpi@...r.kernel.org, linux-nvdimm@...ts.01.org,
        linux-s390@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Kees Cook <keescook@...omium.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Pankaj Gupta <pankaj.gupta.linux@...il.com>,
        Baoquan He <bhe@...hat.com>,
        Wei Yang <richardw.yang@...ux.intel.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Thomas Gleixner <tglx@...utronix.de>, kexec@...ts.infradead.org
Subject: Re: [PATCH v2 2/7] kernel/resource: move and rename
 IORESOURCE_MEM_DRIVER_MANAGED

On Tue, Sep 08, 2020 at 10:10:07PM +0200, David Hildenbrand wrote:
> IORESOURCE_MEM_DRIVER_MANAGED currently uses an unused PnP bit, which is
> always set to 0 by hardware. This is far from beautiful (and confusing),
> and the bit only applies to SYSRAM. So let's move it out of the
> bus-specific (PnP) defined bits.
> 
> We'll add another SYSRAM specific bit soon. If we ever need more bits for
> other purposes, we can steal some from "desc", or reshuffle/regroup what we
> have.
> 
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Jason Gunthorpe <jgg@...pe.ca>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Ard Biesheuvel <ardb@...nel.org>
> Cc: Pankaj Gupta <pankaj.gupta.linux@...il.com>
> Cc: Baoquan He <bhe@...hat.com>
> Cc: Wei Yang <richardw.yang@...ux.intel.com>
> Cc: Eric Biederman <ebiederm@...ssion.com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: kexec@...ts.infradead.org
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  include/linux/ioport.h | 4 +++-
>  kernel/kexec_file.c    | 2 +-
>  mm/memory_hotplug.c    | 4 ++--
>  3 files changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index 52a91f5fa1a36..d7620d7c941a0 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -58,6 +58,9 @@ struct resource {
>  #define IORESOURCE_EXT_TYPE_BITS 0x01000000	/* Resource extended types */
>  #define IORESOURCE_SYSRAM	0x01000000	/* System RAM (modifier) */
>  
> +/* IORESOURCE_SYSRAM specific bits. */
> +#define IORESOURCE_SYSRAM_DRIVER_MANAGED	0x02000000 /* Always detected via a driver. */
> +

Can't you use BIT() here?

thanks,

greg k-h