Date:   Mon, 1 Jun 2020 00:13:21 +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 00:05, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
>
>
>
> On Sunday, May 31, 2020, Vladimir Oltean <olteanv@...il.com> 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
>>
>
> All of this seems an ABI change.
> But also see below.
>

Yes, indeed. What should I understand from your comment though?

>>
>> Fixes: 8d84b18f5678 ("devres: always use dev_name() in devm_ioremap_resource()")
>> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
>> ---
>>  lib/devres.c | 17 ++++++++++++++++-
>>  1 file changed, 16 insertions(+), 1 deletion(-)
>>
>> diff --git a/lib/devres.c b/lib/devres.c
>> index 6ef51f159c54..3d67588c15a7 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 +130,21 @@ __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) {
>> +               int len = strlen(dev_name(dev)) + strlen(res->name) + 2;
>> +
>> +               pretty_name = devm_kzalloc(dev, len, GFP_KERNEL);
>> +               if (!pretty_name)
>> +                       return IOMEM_ERR_PTR(-ENOMEM);
>> +
>> +               sprintf(pretty_name, "%s %s", dev_name(dev), res->name);
>
>
> Reimplementing devm_kasprintf(), why?
>

Mostly because I didn't remember how it was called, thanks for pointing it out.

>>
>> +       } else {
>> +               pretty_name = devm_kstrdup(dev, dev_name(dev), GFP_KERNEL);
>> +               if (!pretty_name)
>> +                       return IOMEM_ERR_PTR(-ENOMEM);
>> +       }
>> +
>> +       if (!devm_request_mem_region(dev, res->start, size, pretty_name)) {
>>                 dev_err(dev, "can't request region for resource %pR\n", res);
>>                 return IOMEM_ERR_PTR(-EBUSY);
>>         }
>> --
>> 2.25.1
>>
>
>
> --
> With Best Regards,
> Andy Shevchenko
>
>

Thanks,
-Vladimir

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