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

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Date:   Sat, 30 May 2020 23:06:30 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     gregkh@...uxfoundation.org, arnd@...db.de,
        akpm@...ux-foundation.org
Cc:     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: [PATCH] devres: keep both device name and resource name in pretty name

From: Vladimir Oltean <vladimir.oltean@....com>

Some device drivers have many memory regions, and sometimes debugging is
easiest using devmem on its register map. 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 said patch, 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

It is 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>
---
 lib/devres.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/lib/devres.c b/lib/devres.c
index 6ef51f159c54..25b78b0cb5cc 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 +130,16 @@ __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);
+		sprintf(pretty_name, "%s %s", dev_name(dev), res->name);
+	} else {
+		pretty_name = devm_kstrdup(dev, dev_name(dev), GFP_KERNEL);
+	}
+
+	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