Re: [Outreachy kernel] Re: [PATCH v6] staging: xgifb: correct the multiple line dereference

[Julia Lawall <julia.lawall@lip6.fr>]

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On Tue, 28 Feb 2017, Arushi Singhal wrote:

>
>
> On Tue, Feb 28, 2017 at 11:21 AM, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
>       On Tue, Feb 28, 2017 at 10:35:30AM +0530, Arushi Singhal wrote:
>       > Error reported by checkpatch.pl as "avoid multiple line dereference".
>       > Addition of new variables to make the code more readable and also to
>       > correct about mentioned error as by itroducing new variables line is
>       > not exceeding 80 characters.
>       >
>       > Signed-off-by: Arushi Singhal <arushisinghal19971997@gmail.com>
>       > ---
>       > changes in v6
>       >   - changes done such that no other errors can generate.
>       >   - Improve the coding style.
>       >   - Introduced new variables.
>       >   - type of the variable is changed.
>       >
>       >  drivers/staging/xgifb/XGI_main_26.c | 29 ++++++-----------------------
>       >  drivers/staging/xgifb/vb_setmode.c  | 17 +++++++++++------
>       >  2 files changed, 17 insertions(+), 29 deletions(-)
>       >
>       > diff --git a/drivers/staging/xgifb/XGI_main_26.c b/drivers/staging/xgifb/XGI_main_26.c
>       > index 69ed137337ce..9870ea3b76b4 100644
>       > --- a/drivers/staging/xgifb/XGI_main_26.c
>       > +++ b/drivers/staging/xgifb/XGI_main_26.c
>       > @@ -878,30 +878,13 @@ static void XGIfb_post_setmode(struct xgifb_video_info *xgifb_info)
>       >                       }
>       >
>       >                       if ((filter >= 0) && (filter <= 7)) {
>       > +                             const u8 *f = XGI_TV_filter[filter_tb].filter[filter];
>       >                               pr_debug("FilterTable[%d]-%d: %*ph\n",
>       > -                                      filter_tb, filter,
>       > -                                      4, XGI_TV_filter[filter_tb].
>       > -                                                filter[filter]);
>       > -                             xgifb_reg_set(
>       > -                                     XGIPART2,
>       > -                                     0x35,
>       > -                                     (XGI_TV_filter[filter_tb].
>       > -                                             filter[filter][0]));
>       > -                             xgifb_reg_set(
>       > -                                     XGIPART2,
>       > -                                     0x36,
>       > -                                     (XGI_TV_filter[filter_tb].
>       > -                                             filter[filter][1]));
>       > -                             xgifb_reg_set(
>       > -                                     XGIPART2,
>       > -                                     0x37,
>       > -                                     (XGI_TV_filter[filter_tb].
>       > -                                             filter[filter][2]));
>       > -                             xgifb_reg_set(
>       > -                                     XGIPART2,
>       > -                                     0x38,
>       > -                                     (XGI_TV_filter[filter_tb].
>       > -                                             filter[filter][3]));
>       > +                                      filter_tb, filter, 4, f);
>       > +                             xgifb_reg_set(XGIPART2, 0x35, f[0]);
>       > +                             xgifb_reg_set(XGIPART2, 0x36, f[1]);
>       > +                             xgifb_reg_set(XGIPART2, 0x37, f[2]);
>       > +                             xgifb_reg_set(XGIPART2, 0x38, f[3]);
>       >                       }
>       >               }
>       >       }
>       > diff --git a/drivers/staging/xgifb/vb_setmode.c b/drivers/staging/xgifb/vb_setmode.c
>       > index 7c7c8c8f1df3..249a32804c06 100644
>       > --- a/drivers/staging/xgifb/vb_setmode.c
>       > +++ b/drivers/staging/xgifb/vb_setmode.c
>       > @@ -221,8 +221,11 @@ static unsigned char XGI_AjustCRT2Rate(unsigned short ModeIdIndex,
>       >
>       >       for (; XGI330_RefIndex[RefreshRateTableIndex + (*i)].ModeID ==
>       >              tempbx; (*i)--) {
>       > -             infoflag = XGI330_RefIndex[RefreshRateTableIndex + (*i)].
>       > -                             Ext_InfoFlag;
>       > +             unsigned short j;
>       > +
>       > +             j = XGI330_RefIndex[RefreshRateTableIndex + (*i)].Ext_InfoFlag;
>       > +             infoflag = j;
>       > +
>       >               if (infoflag & tempax)
>       >                       return 1;
>
>
> Why are you using a temporary variable 'j' here?  It's not needed at
> all, and just is confusing to read the code now, don't you agree?
>
>
> I am using temporary variable of small size(character) so that when
> I fixed the multiple line dereference then the line number of characters in a line will
> not increase by 80.

I agree with Greg that this is not a readable solution.  Putting the whole
thing on one line would be better, even if it goes over 80 characters.
Having the field on a line by itself is much worse, because then it looks
like a variable name - one doesn't easily see the connection to the
structure.  Hopefully someone will come up with a shorter name for
RefreshRateTableIndex and then the problem will be completely solved.
Maybe ref_table_index?  Although to me ref looks like reference, not
refresh...

julia

>  
>       > @@ -231,8 +234,11 @@ static unsigned char XGI_AjustCRT2Rate(unsigned short ModeIdIndex,
>       >       }0
>       >
>       >       for ((*i) = 0;; (*i)++) {
>       > -             infoflag = XGI330_RefIndex[RefreshRateTableIndex + (*i)].
>       > -                             Ext_InfoFlag;
>       > +             unsigned short m;
>       > +
>       > +             m = XGI330_RefIndex[RefreshRateTableIndex + (*i)].Ext_InfoFlag;
>       > +             infoflag = m;
>       > +
>       >               if (XGI330_RefIndex[RefreshRateTableIndex + (*i)].ModeID
>       >                               != tempbx) {
>       >                       return 0;
>
>       Same here, why add a new variable that isn't used more than once?  You
>       are trying to work around something that doesn't make sense to work
>       around.
>
> Same reason as above.
> Thanks
> Arushi
>  
>       Remember, coding style cleanups are to be done to make the code easier
>       to understand and follow.  Not to blindly follow a perl script that
>       can not think.  Sometimes it is not right...
>
>       thanks,
>
>       greg k-h
>
>
>
>  
>
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