netdev - Re: [PATCH v3] devres: keep both device name and resource name in pretty name

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Date:   Mon, 1 Jun 2020 13:13:16 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        sergei.shtylyov@...entembedded.com, bgolaszewski@...libre.com,
        mika.westerberg@...ux.intel.com, efremov@...ux.com,
        ztuowen@...il.com, lkml <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH v3] devres: keep both device name and resource name in
 pretty name

Hi Greg,

On Mon, 1 Jun 2020 at 13:04, Greg KH <gregkh@...uxfoundation.org> wrote:
>
> On Mon, Jun 01, 2020 at 12:58:26PM +0300, Vladimir Oltean wrote:
> > From: Vladimir Oltean <vladimir.oltean@....com>
> >
> > 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
>
> As this is changing the format of a user-visable file, what tools just
> broke that are used to parsing the old format?
>

All the same tools that broke after 8d84b18f5678 was merged. I am not
entirely sure why the 'stable ABI' argument was not brought up there
as well.

> And are you sure about this?  That's not how my system looks at all, I
> have fun things like:
>
>    ac000000-da0fffff : PCI Bus 0000:03
>     ac000000-da0fffff : PCI Bus 0000:04
>       ac000000-c3efffff : PCI Bus 0000:06
>       c3f00000-c3ffffff : PCI Bus 0000:39
>         c3f00000-c3f0ffff : 0000:39:00.0
>           c3f00000-c3f0ffff : xhci-hcd
>       c4000000-d9ffffff : PCI Bus 0000:3a
>         c4000000-d9ffffff : PCI Bus 0000:3b
>           c4000000-c40fffff : PCI Bus 0000:3c
>           c4000000-c400ffff : 0000:3c:00.0
>           c4000000-c400ffff : xhci-hcd
>           c4010000-c4010fff : 0000:3c:00.0
>           c4011000-c4011fff : 0000:3c:00.0
>           c4100000-c41fffff : PCI Bus 0000:3d
>           c4100000-c410ffff : 0000:3d:00.0
>           c4100000-c410ffff : xhci-hcd
>           c4110000-c4110fff : 0000:3d:00.0
>           c4111000-c4111fff : 0000:3d:00.0
>           c4200000-c42fffff : PCI Bus 0000:3e
>           c4200000-c4207fff : 0000:3e:00.0
>           c4200000-c4207fff : xhci-hcd
>           c4300000-c43fffff : PCI Bus 0000:3f
>           c4300000-c437ffff : 0000:3f:00.0
>           c4380000-c4383fff : 0000:3f:00.0
>           c4400000-d9ffffff : PCI Bus 0000:40
>       da000000-da0fffff : PCI Bus 0000:05
>         da000000-da03ffff : 0000:05:00.0
>         da040000-da040fff : 0000:05:00.0
>
>
> which is a mix of the resources in some places, and just driver names in
> others.
>
> But, that does imply that your change will not break anything as the
> parsing of this mess is probably just "anything after the ':'
> character...
>
> thanks,
>
> greg k-h

With this patch you'll just have more (potentially redundant)
information. I'm not really sure how to satisfy everyone here. I was
completely fine with pre-8d84b18f5678 behavior.

Thanks,
-Vladimir