linux-kernel - Re: [PATCH 3/4] cdx: create sysfs resource files

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Message-ID: <2023071231-drinking-unskilled-3c00@gregkh>
Date:   Wed, 12 Jul 2023 17:11:06 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     "Gangurde, Abhijit" <abhijit.gangurde@....com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Gupta, Nipun" <Nipun.Gupta@....com>,
        "Agarwal, Nikhil" <nikhil.agarwal@....com>,
        "Gupta, Puneet (DCG-ENG)" <puneet.gupta@....com>,
        "git (AMD-Xilinx)" <git@....com>,
        "Simek, Michal" <michal.simek@....com>,
        "Jansen Van Vuuren, Pieter" <pieter.jansen-van-vuuren@....com>
Subject: Re: [PATCH 3/4] cdx: create sysfs resource files

On Wed, Jul 12, 2023 at 01:23:28PM +0000, Gangurde, Abhijit wrote:
> [AMD Official Use Only - General]
> 
> > > Resource files provides the basic MMIO regions info to the
> > > user-space. Also, resources<x> devices can be used to mmap the
> > > MMIO regions in the user-space.
> > >
> > > Co-developed-by: Puneet Gupta <puneet.gupta@....com>
> > > Signed-off-by: Puneet Gupta <puneet.gupta@....com>
> > > Co-developed-by: Nipun Gupta <nipun.gupta@....com>
> > > Signed-off-by: Nipun Gupta <nipun.gupta@....com>
> > > Signed-off-by: Abhijit Gangurde <abhijit.gangurde@....com>
> > > Reviewed-by: Pieter Jansen van Vuuren <pieter.jansen-van-
> > vuuren@....com>
> > > Tested-by: Nikhil Agarwal <nikhil.agarwal@....com>
> > > ---
> > >  Documentation/ABI/testing/sysfs-bus-cdx |  15 +++
> > >  drivers/cdx/cdx.c                       | 139 +++++++++++++++++++++++-
> > >  include/linux/cdx/cdx_bus.h             |  10 ++
> > >  3 files changed, 163 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/Documentation/ABI/testing/sysfs-bus-cdx
> > b/Documentation/ABI/testing/sysfs-bus-cdx
> > > index d9e00058471d..6ca47b6442ce 100644
> > > --- a/Documentation/ABI/testing/sysfs-bus-cdx
> > > +++ b/Documentation/ABI/testing/sysfs-bus-cdx
> > > @@ -76,3 +76,18 @@ Description:
> > >             For example::
> > >
> > >               # echo 1 > /sys/bus/cdx/devices/.../remove
> > > +
> > > +What:              /sys/bus/cdx/devices/.../resource
> > > +Date:              July 2023
> > > +Contact:   puneet.gupta@....com
> > > +Description:
> > > +           The resource file contains host addresses of CDX device
> > > +           resources. Each line of the resource file describes a region
> > > +           with start, end, and flag fields.
> >
> > If you documented what this file looked like here, it would be obvious
> > that this is not an acceptable sysfs file in any sense of the word.
> >
> > Please do so, and then fix the patch to not do that at all.
> 
> Similar interface exist for pci and we intended to keep it same way. Could you please elaborate on this.
> 
> # cat /sys/bus/pci/devices/0000\:01\:00.0/resource
> 0x0000000092100000 0x00000000921fffff 0x000000000014220c
> 0x0000000000000000 0x0000000000000000 0x0000000000000000

Please don't propagate incorrect decisions in the past.

Why do you need all of these "resources" in userspace?  What tool is
going to read and parse them and do something with them?

This really violates the "one value per file" sysfs rule, you are going
to have to have a huge reason why this is not applicable here, AND you
are going to have to document it very very well and get everyone to
agree with it.

thanks,

greg k-h