Re: [Outreachy kernel] [PATCH] Staging: rtl8188eu: core: Use list_entry instead of container_of

[Julia Lawall]

On Sat, 30 Sep 2017, Srishti Sharma wrote:

> On Sat, Sep 30, 2017 at 10:35 AM, Julia Lawall <julia.lawall@xxxxxxx> 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.

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@xxxxxxxxx>
> >> ---
> >>  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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>