linux-kernel - Re: [PATCH v2] devres: keep both device name and resource name in pretty name

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Date:   Mon, 1 Jun 2020 13:43:57 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "arnd@...db.de" <arnd@...db.de>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "sergei.shtylyov@...entembedded.com" 
        <sergei.shtylyov@...entembedded.com>,
        "bgolaszewski@...libre.com" <bgolaszewski@...libre.com>,
        "mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>,
        "efremov@...ux.com" <efremov@...ux.com>,
        "ztuowen@...il.com" <ztuowen@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH v2] devres: keep both device name and resource name in
 pretty name

On Mon, 1 Jun 2020 at 13:39, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
>
> On Mon, Jun 1, 2020 at 12:13 AM Vladimir Oltean <olteanv@...il.com> wrote:
> > On Mon, 1 Jun 2020 at 00:05, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
> > > On Sunday, May 31, 2020, Vladimir Oltean <olteanv@...il.com> wrote:
>
> > >> Sometimes debugging a device is easiest using devmem on its register
> > >> map, and that can be seen with /proc/iomem. But some device drivers have
> > >> many memory regions. Take for example a networking switch. Its memory
> > >> map used to look like this in /proc/iomem:
> > >>
> > >> 1fc000000-1fc3fffff : pcie@...000000
> > >>   1fc000000-1fc3fffff : 0000:00:00.5
> > >>     1fc010000-1fc01ffff : sys
> > >>     1fc030000-1fc03ffff : rew
> > >>     1fc060000-1fc0603ff : s2
> > >>     1fc070000-1fc0701ff : devcpu_gcb
> > >>     1fc080000-1fc0800ff : qs
> > >>     1fc090000-1fc0900cb : ptp
> > >>     1fc100000-1fc10ffff : port0
> > >>     1fc110000-1fc11ffff : port1
> > >>     1fc120000-1fc12ffff : port2
> > >>     1fc130000-1fc13ffff : port3
> > >>     1fc140000-1fc14ffff : port4
> > >>     1fc150000-1fc15ffff : port5
> > >>     1fc200000-1fc21ffff : qsys
> > >>     1fc280000-1fc28ffff : ana
> > >>
> > >> But after the patch in Fixes: was applied, the information is now
> > >> presented in a much more opaque way:
> > >>
> > >> 1fc000000-1fc3fffff : pcie@...000000
> > >>   1fc000000-1fc3fffff : 0000:00:00.5
> > >>     1fc010000-1fc01ffff : 0000:00:00.5
> > >>     1fc030000-1fc03ffff : 0000:00:00.5
> > >>     1fc060000-1fc0603ff : 0000:00:00.5
> > >>     1fc070000-1fc0701ff : 0000:00:00.5
> > >>     1fc080000-1fc0800ff : 0000:00:00.5
> > >>     1fc090000-1fc0900cb : 0000:00:00.5
> > >>     1fc100000-1fc10ffff : 0000:00:00.5
> > >>     1fc110000-1fc11ffff : 0000:00:00.5
> > >>     1fc120000-1fc12ffff : 0000:00:00.5
> > >>     1fc130000-1fc13ffff : 0000:00:00.5
> > >>     1fc140000-1fc14ffff : 0000:00:00.5
> > >>     1fc150000-1fc15ffff : 0000:00:00.5
> > >>     1fc200000-1fc21ffff : 0000:00:00.5
> > >>     1fc280000-1fc28ffff : 0000:00:00.5
> > >>
> > >> That patch made a fair comment that /proc/iomem might be confusing when
> > >> it shows resources without an associated device, but we can do better
> > >> than just hide the resource name altogether. Namely, we can print the
> > >> device name _and_ the resource name. Like this:
> > >>
> > >> 1fc000000-1fc3fffff : pcie@...000000
> > >>   1fc000000-1fc3fffff : 0000:00:00.5
> > >>     1fc010000-1fc01ffff : 0000:00:00.5 sys
> > >>     1fc030000-1fc03ffff : 0000:00:00.5 rew
> > >>     1fc060000-1fc0603ff : 0000:00:00.5 s2
> > >>     1fc070000-1fc0701ff : 0000:00:00.5 devcpu_gcb
> > >>     1fc080000-1fc0800ff : 0000:00:00.5 qs
> > >>     1fc090000-1fc0900cb : 0000:00:00.5 ptp
> > >>     1fc100000-1fc10ffff : 0000:00:00.5 port0
> > >>     1fc110000-1fc11ffff : 0000:00:00.5 port1
> > >>     1fc120000-1fc12ffff : 0000:00:00.5 port2
> > >>     1fc130000-1fc13ffff : 0000:00:00.5 port3
> > >>     1fc140000-1fc14ffff : 0000:00:00.5 port4
> > >>     1fc150000-1fc15ffff : 0000:00:00.5 port5
> > >>     1fc200000-1fc21ffff : 0000:00:00.5 qsys
> > >>     1fc280000-1fc28ffff : 0000:00:00.5 ana
>
> > > All of this seems an ABI change.
>
> > Yes, indeed. What should I understand from your comment though?
>
> You effectively break an ABI.
>
> --
> With Best Regards,
> Andy Shevchenko

I've replied to Greg about this in the v3 patch.

Regards,
-Vladimir