linux-kernel - Re: [Outreachy kernel] [PATCH] Staging: rtl8188eu: core: Use list_entry instead of container

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Date:   Sat, 30 Sep 2017 08:21:56 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     Srishti Sharma <srishtishar@...il.com>
cc:     Greg KH <gregkh@...uxfoundation.org>, devel@...verdev.osuosl.org,
        Linux kernel mailing list <linux-kernel@...r.kernel.org>,
        outreachy-kernel <outreachy-kernel@...glegroups.com>
Subject: Re: [Outreachy kernel] [PATCH] Staging: rtl8188eu: core: Use list_entry
 instead of container_of



On Sat, 30 Sep 2017, Srishti Sharma wrote:

> On Sat, Sep 30, 2017 at 11:36 AM, Julia Lawall <julia.lawall@...6.fr> wrote:
> >
> >
> > On Sat, 30 Sep 2017, Srishti Sharma wrote:
> >
> >> On Sat, Sep 30, 2017 at 10:35 AM, Julia Lawall <julia.lawall@...6.fr> wrote:
> >> >
> >> >
> >> > On Sat, 30 Sep 2017, Srishti Sharma wrote:
> >> >
> >> >> For variables of the type struct list_head* use list_entry to access
> >> >> the current list element instead of using container_of.
> >> >> Done using the following semantic patch by coccinelle.
> >> >>
> >> >> @r@
> >> >> identifier e;
> >> >> struct list_head* l;
> >> >> @@
> >> >>
> >> >> <... when != l == NULL
> >> >> l;
> >> >> ...>
> >> > I don't see what is the goal of the above code.  The list_head variable is
> >> > not going to be in a statement by itself.  There is also no need to check
> >> > for l being NULL.  If it is NULL, the original code is incorrect too.
> >>
> >> Since only those container_of are to replaced with list_entry which
> >> have a variable of type list_head*  , I wanted to check if it occurs
> >> anywhere before
> >> container_of ,
> >
> > Why?  If it is a list, then it seems appropriate to access it using
> > list_head.
> >
> >> which it only does in it's declaration , because it
> >> can't be in any
> >> statement by itself . I think it will be better to write .
> >>
> >> @r@
> >> identifier e;
> >> struct list_head* l;
> >> @@
> >>
> >> <...
> >> container_of(l,...);
> >> ...>
> >
> > This doesn't ensure that there is a preceding container_of, if that is
> > what you are trying to do.  The problem is that <... P ...> finds 0 or
> > more occurrences of pattern P, not 1 or more occurrences.  1 or more
> > occurrences is <+... P ...+>.  But it would be simpler if you want an
> > occurrence of container_of before the thing you are transforming to put
> >
> > container_of(l,...);
> > ...
> > e = ...
> >
> > But this doesn't make sense either, partly because the preceding
> > container_of is just not needed, and also because a container_of would not
> > be in a statement by itself.  In Coccinelle, when you put a ; after
> > something is means that the thing is a complete statement, not just the
> > end half of a statement.
>
> So , I guess we can simply write.
>
> e =
> -container_of
> +list_entry
>      (l,...)

Yes.  You don't even need the e =.  As long as there is a call to
container_of on a list_head * value, you can change it.

julia

>
> Regards,
> Srishti
>
> >
> > julia
> >
> >> e =
> >> -container_of
> >> +list_entry
> >>      (
> >>       ....)
> >>
> >> >> (
> >> >> e =
> >> >> -container_of
> >> >> +list_entry
> >> >>      (
> >> >>       ...)
> >> >> )
> >> >
> >> > Here you don't need the outer ( ).  This makes a disjunction with only
> >> > one choice.  Since there is only one choice, you don't need the
> >> > disjunction.
> >>
> >> Thanks a lot , for pointing out the errors .
> >>
> >> Regards,
> >> Srishti
> >> > julia
> >> >
> >> >> Signed-off-by: Srishti Sharma <srishtishar@...il.com>
> >> >> ---
> >> >>  drivers/staging/rtl8188eu/core/rtw_sta_mgt.c | 12 ++++++------
> >> >>  1 file changed, 6 insertions(+), 6 deletions(-)
> >> >>
> >> >> diff --git a/drivers/staging/rtl8188eu/core/rtw_sta_mgt.c b/drivers/staging/rtl8188eu/core/rtw_sta_mgt.c
> >> >> index 22cf362..f9df4ac 100644
> >> >> --- a/drivers/staging/rtl8188eu/core/rtw_sta_mgt.c
> >> >> +++ b/drivers/staging/rtl8188eu/core/rtw_sta_mgt.c
> >> >> @@ -152,8 +152,8 @@ u32       _rtw_free_sta_priv(struct       sta_priv *pstapriv)
> >> >>                       while (phead != plist) {
> >> >>                               int i;
> >> >>
> >> >> -                             psta = container_of(plist, struct sta_info,
> >> >> -                                                 hash_list);
> >> >> +                             psta = list_entry(plist, struct sta_info,
> >> >> +                                               hash_list);
> >> >>                               plist = plist->next;
> >> >>
> >> >>                               for (i = 0; i < 16; i++) {
> >> >> @@ -323,7 +323,7 @@ u32       rtw_free_stainfo(struct adapter *padapter, struct sta_info *psta)
> >> >>               plist = phead->next;
> >> >>
> >> >>               while (!list_empty(phead)) {
> >> >> -                     prframe = container_of(plist, struct recv_frame, list);
> >> >> +                     prframe = list_entry(plist, struct recv_frame, list);
> >> >>
> >> >>                       plist = plist->next;
> >> >>
> >> >> @@ -399,7 +399,7 @@ void rtw_free_all_stainfo(struct adapter *padapter)
> >> >>               plist = phead->next;
> >> >>
> >> >>               while (phead != plist) {
> >> >> -                     psta = container_of(plist, struct sta_info, hash_list);
> >> >> +                     psta = list_entry(plist, struct sta_info, hash_list);
> >> >>
> >> >>                       plist = plist->next;
> >> >>
> >> >> @@ -435,7 +435,7 @@ struct sta_info *rtw_get_stainfo(struct sta_priv *pstapriv, u8 *hwaddr)
> >> >>       plist = phead->next;
> >> >>
> >> >>       while (phead != plist) {
> >> >> -             psta = container_of(plist, struct sta_info, hash_list);
> >> >> +             psta = list_entry(plist, struct sta_info, hash_list);
> >> >>
> >> >>               if ((!memcmp(psta->hwaddr, addr, ETH_ALEN)) == true) {
> >> >>                       /*  if found the matched address */
> >> >> @@ -493,7 +493,7 @@ u8 rtw_access_ctrl(struct adapter *padapter, u8 *mac_addr)
> >> >>       phead = get_list_head(pacl_node_q);
> >> >>       plist = phead->next;
> >> >>       while (phead != plist) {
> >> >> -             paclnode = container_of(plist, struct rtw_wlan_acl_node, list);
> >> >> +             paclnode = list_entry(plist, struct rtw_wlan_acl_node, list);
> >> >>               plist = plist->next;
> >> >>
> >> >>               if (!memcmp(paclnode->addr, mac_addr, ETH_ALEN)) {
> >> >> --
> >> >> 2.7.4
> >> >>
> >> >> --
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> >>
>
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