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

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Date:   Mon, 1 Jun 2020 21:48:35 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Vladimir Oltean <olteanv@...il.com>, gregkh@...uxfoundation.org,
        arnd@...db.de, akpm@...ux-foundation.org
Cc:     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 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