linux-kernel - Re: [PATCH] coccinelle: semantic patch for missing of_node

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Date:   Tue, 7 May 2019 17:27:15 +0200
From:   Markus Elfring <Markus.Elfring@....de>
To:     Wen Yang <wen.yang99@....com.cn>, cocci@...teme.lip6.fr
Cc:     linux-kernel@...r.kernel.org,
        Gilles Muller <Gilles.Muller@...6.fr>,
        Julia Lawall <julia.lawall@...6.fr>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        Yi Wang <wang.yi59@....com.cn>
Subject: Re: [PATCH] coccinelle: semantic patch for missing of_node_put

> The call to of_parse_phandle()/of_find_node_by_name() ... returns a node
> pointer with refcount incremented thus it must be explicitly decremented
> after the last usage.
>
> This SmPL is also looking for places where there is an of_node_put on
> some path but not on others.

I suggest to improve this commit description.

* Possible wording:
  There are functions which increment a reference counter for a device node.
  These functions belong to a programming interface for the management
  of information from device trees.
  The counter must be decremented after the last usage of a device node.

  This SmPL script looks also for places where a of_node_put() call is on
  some paths but not on others.

* Will the word “patch” be replaced by “code search” in the commit subject
  because the operation modes “report” and “org” are supported here?

> +@...tialize:python@
> +@@

Such a SmPL rule would apply to every possible operation mode.
I have noticed then that the two Python variables from here will be needed
only in two SmPL rules which depend on the mode “report”.

* Thus I would prefer to adjust the dependency specification accordingly.

* Please replace these variables by a separate function like
  the following.
  def display1(p1 ,p2):
     if add_if_not_present(p1[0].line, p2[0].line):
        coccilib.report.print_report(p2[0],
                                     "prefix"
                                     + p1[0].line
                                     + "suffix")

* Please move another bit of duplicate code to a separate function like
  the following.
  def display2(p1 ,p2):
     cocci.print_main("Choose info 1", p1)
     cocci.print_secs("Choose info 2", p2)

> +x = @p1\(of_find_compatible_node\|of_find_node_by_name\|of_parse_phandle\|

If you would like to insist to use such a SmPL disjunction, I would prefer
an other code formatting here.
How do you think about to put each function name on a separate line?

Can such a name list be ever automatically determined from an other
information source?
(Are there circumstances to consider under which the application of
a detailed regular expression would become interesting for a SmPL constraint?)

Will it be influenced by any sort criteria?

> +    when != of_node_put(x)
…
> +    when != if (x) { ... of_node_put(x) ... }

I find the second when constraint specification unnecessary because
the previous one should be sufficient to exclude such a function call.

Can the specification “when != \( of_node_put \| of_get_next_parent \) (x)”
be useful?

> +return x;
> +|
> +return of_fwnode_handle(x);

Can it be nicer to merge this bit of code into another SmPL disjunction?

+return \( x \| of_fwnode_handle(x) \);

Regards,
Markus