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

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Date:   Mon, 1 Jun 2020 12:04:41 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     arnd@...db.de, akpm@...ux-foundation.org,
        sergei.shtylyov@...entembedded.com, bgolaszewski@...libre.com,
        mika.westerberg@...ux.intel.com, efremov@...ux.com,
        ztuowen@...il.com, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH v3] devres: keep both device name and resource name in
 pretty name

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?

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