linux-kernel - [PATCH 0/2 v3] drivers: introduce automatic cleanup feature

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Message-Id: <20240501094313.407820-1-vincenzo.mezzela@gmail.com>
Date: Wed,  1 May 2024 11:43:11 +0200
From: Vincenzo Mezzela <vincenzo.mezzela@...il.com>
To: sudeep.holla@....com
Cc: gregkh@...uxfoundation.org,
	javier.carrasco.cruz@...il.com,
	julia.lawall@...ia.fr,
	linux-kernel@...r.kernel.org,
	rafael@...nel.org,
	skhan@...uxfoundation.org,
	vincenzo.mezzela@...il.com
Subject: [PATCH 0/2 v3] drivers: introduce automatic cleanup feature

This patch series introduces the automatic cleanup feature using the __free
attribute. With this modification, resources allocated with __free are 
automatically released at the end of the scope.

In some cases, modifying the structure of loops is necessary to utilize the
__free attribute effectively. For example:

```
struct device_node *t;

do {
    t = of_get_child_by_name(..);
    if (t) {

        // some code here

        of_node_put(t);
    }
    i++;

} while (t);

//       ^
//       |
//  device_node here
```

To use the __free attribute here, we need to move the declaration of the device_node
within the loop, otherwise the automatic cleanup is called only at the end of the
function, and not at end of each iteration of the loop, being it scope-based. 

However, moving the declaration of the device_node within the loop, we can no
longer check the exit condition in the loop statement, being it outside
the loop's scope.

Therefore, this work is split into two patches. The first patch moves the exit
condition of the loop directly within the loop's scope with an explicit break
statement:

```
struct device_node *t;

do {
    t = of_get_child_by_name(..);
    if (!t)
        break;

    // some code here

    of_node_put(t);
    i++;

} while (1);
```
The second patch eliminates all of_node_put() calls, introducing the __free 
attribute to the device_node.

changes in v2:
    - check loop exit condition within the loop
    - add cleanup.h header

changes in v3:
    - split patch in two
    - fix misalignment
    - fix checkpatch warnings
    - replace break with return statement where possible

Vincenzo Mezzela (2):
  drivers: reorganize do-while loops
  drivers: use __free attribute instead of of_node_put()

 drivers/base/arch_topology.c | 140 +++++++++++++++++------------------
 1 file changed, 67 insertions(+), 73 deletions(-)

-- 
2.34.1