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

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Message-ID: <CA+h21hotyQhJeMLJz5SaNc+McRF=w2m4m_qAAQV2D6phE6apkA@mail.gmail.com>
Date:   Mon, 1 Jun 2020 23:03:27 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        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 Sergei,

On Mon, 1 Jun 2020 at 21:48, Sergei Shtylyov
<sergei.shtylyov@...entembedded.com> wrote:
>
> On 06/01/2020 12:58 PM, 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
> >
> > Fixes: 8d84b18f5678 ("devres: always use dev_name() in devm_ioremap_resource()")
> > Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
> > ---
> > Changes in v2:
> > Checking for memory allocation errors and returning -ENOMEM.
> >
> > Changes in v3:
> > Using devm_kasprintf instead of open-coding it.
> >
> >  lib/devres.c | 11 ++++++++++-
> >  1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/lib/devres.c b/lib/devres.c
> > index 6ef51f159c54..ca0d28727cce 100644
> > --- a/lib/devres.c
> > +++ b/lib/devres.c
> > @@ -119,6 +119,7 @@ __devm_ioremap_resource(struct device *dev, const struct resource *res,
> >  {
> >       resource_size_t size;
> >       void __iomem *dest_ptr;
> > +     char *pretty_name;
> >
> >       BUG_ON(!dev);
> >
> > @@ -129,7 +130,15 @@ __devm_ioremap_resource(struct device *dev, const struct resource *res,
> >
> >       size = resource_size(res);
> >
> > -     if (!devm_request_mem_region(dev, res->start, size, dev_name(dev))) {
> > +     if (res->name)
> > +             pretty_name = devm_kasprintf(dev, GFP_KERNEL, "%s %s",
>
>    What about "%s:%s"? I suspect it'd be better on the ABI side of things?
>
> [...]
>
> MBR, Sergei

I don't have a particular preference, but out of curiosity, why would
it be better?

Thanks,
-Vladimir