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

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Message-ID: <1839b906-2e1a-4340-0da8-04b603a96ca1@cogentembedded.com>
Date:   Mon, 1 Jun 2020 23:11:30 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Vladimir Oltean <olteanv@...il.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

On 06/01/2020 11:03 PM, Vladimir Oltean wrote:
> 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?

   No space amidst the name.

> Thanks,
> -Vladimir

MBR, Sergei