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From:   "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
To:     Julia Lawall <julia.lawall@inria.fr>
Cc:     Dan Carpenter <dan.carpenter@oracle.com>,
        outreachy-kernel@googlegroups.com,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [Outreachy kernel] [PATCH] :staging: rtl8723bs: Remove useless led_blink_hdl()
Date:   Tue, 13 Apr 2021 21:16:28 +0200
Message-ID: <2400087.QbMOWSuNhY@linux.local>
In-Reply-To: <alpine.DEB.2.22.394.2104132056470.14108@hadrien>
References: <20210413155908.8691-1-fmdefrancesco@gmail.com> <4666345.5ezhEZ0rgB@linux.local> <alpine.DEB.2.22.394.2104132056470.14108@hadrien>
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On Tuesday, April 13, 2021 8:57:20 PM CEST Julia Lawall wrote:
> On Tue, 13 Apr 2021, Fabio M. De Francesco wrote:
> > On Tuesday, April 13, 2021 8:20:50 PM CEST Dan Carpenter wrote:
> > > On Tue, Apr 13, 2021 at 06:47:06PM +0200, Fabio M. De Francesco 
wrote:
> > > > On Tuesday, April 13, 2021 6:27:17 PM CEST Julia Lawall wrote:
> > > > > On Tue, 13 Apr 2021, Fabio M. De Francesco wrote:
> > > > > > On Tuesday, April 13, 2021 6:04:16 PM CEST Julia Lawall wrote:
> > > > > > > On Tue, 13 Apr 2021, Fabio M. De Francesco wrote:
> > > > > > > > Removed the led_blink_hdl() function (declaration,
> > > > > > > > definition,
> > > > > > > > and
> > > > > > > > caller code) because it's useless. It only seems to check
> > > > > > > > whether
> > > > > > > > or
> > > > > > > > not a given pointer is NULL. There are other (simpler)
> > > > > > > > means
> > > > > > > > for
> > > > > > > > that
> > > > > > > > purpose.
> > > > > > > > 
> > > > > > > > Signed-off-by: Fabio M. De Francesco
> > > > > > > > <fmdefrancesco@gmail.com>
> > > > > > > > ---
> > > > > > > > 
> > > > > > > >  drivers/staging/rtl8723bs/core/rtw_cmd.c         | 1 -
> > > > > > > >  drivers/staging/rtl8723bs/core/rtw_mlme_ext.c    | 9
> > > > > > > >  ---------
> > > > > > > >  drivers/staging/rtl8723bs/include/rtw_mlme_ext.h | 1 -
> > > > > > > >  3 files changed, 11 deletions(-)
> > > > > > > > 
> > > > > > > > diff --git a/drivers/staging/rtl8723bs/core/rtw_cmd.c
> > > > > > > > b/drivers/staging/rtl8723bs/core/rtw_cmd.c index
> > > > > > > > 0297fbad7bce..4c44dfd21514 100644
> > > > > > > > --- a/drivers/staging/rtl8723bs/core/rtw_cmd.c
> > > > > > > > +++ b/drivers/staging/rtl8723bs/core/rtw_cmd.c
> > > > > > > > @@ -150,7 +150,6 @@ static struct cmd_hdl wlancmds[] = {
> > > > > > > > 
> > > > > > > >  	GEN_MLME_EXT_HANDLER(0, h2c_msg_hdl) /*58*/
> > > > > > > >  	GEN_MLME_EXT_HANDLER(sizeof(struct 
SetChannelPlan_param),
> > > > > > > >  	set_chplan_hdl) /*59*/>
> > > > > > > > 
> > > > > > > > -	GEN_MLME_EXT_HANDLER(sizeof(struct 
LedBlink_param),
> > > > > > 
> > > > > > led_blink_hdl)
> > > > > > 
> > > > > > > > /*60*/
> > > > > > > 
> > > > > > > This is worrisome.  Doyou fully understand the impact of
> > > > > > > this?
> > > > > > > If
> > > > > > > not,
> > > > > > > the change is probably not a good idea.
> > > > > > 
> > > > > > This is that macro definition:
> > > > > > 
> > > > > > #define GEN_MLME_EXT_HANDLER(size, cmd) {size, cmd},
> > > > > > 
> > > > > > struct C2HEvent_Header {
> > > > > > 
> > > > > > #ifdef __LITTLE_ENDIAN
> > > > > > 
> > > > > >         unsigned int len:16;
> > > > > >         unsigned int ID:8;
> > > > > >         unsigned int seq:8;
> > > > > > 
> > > > > > #else
> > > > > > 
> > > > > >         unsigned int seq:8;
> > > > > >         unsigned int ID:8;
> > > > > >         unsigned int len:16;
> > > > > > 
> > > > > > #endif
> > > > > > 
> > > > > >         unsigned int rsvd;
> > > > > > 
> > > > > > };
> > > > > > 
> > > > > > It's a bit convoluted with regard to my experience. Probably I
> > > > > > don't
> > > > > > understand it fully, but it seems to me to not having effects
> > > > > > to
> > > > > > the
> > > > > > code where I removed its use within core/rtw_cmd.c.
> > > > > > 
> > > > > > What am I missing?
> > > > > 
> > > > > It seems that the function is being put into an array.  Probably
> > > > > someone
> > > > > expects to find it there.  Probably you have shifted all of the
> > > > > functions that come afterwards back one slot so that they are all
> > > > > in
> > > > > the wrong places.
> > > > > 
> > > > > julia
> > > > 
> > > > Thanks for your explanation. Obviously this implies that the
> > > > function
> > > > cannot be removed, unless one fill the slot that is deleted by to
> > > > not
> > > > calling this macro at the right moment.
> > > > 
> > > > I also suppose that providing a function pointer with a NULL value
> > > > wouldn't work either.
> > > 
> > > It would work.  That array is full of NULL function pointers.
> > 
> > Interesting, thanks.
> > 
> > I'm going to remove that function and replace its name in the macro
> > with a NULL function pointer.
> > 
> > I couldn't believe it would work when I wrote about that.
> 
> Have you checked that a value of NULL in that place is going to have the
> same effect as the function?
>
No, I have not, but perhaps is not relevant.

I want to give to the macro the name of an empty function that I define in 
the same header where there the prototype of led_blink_hdl() is defined 
now: something like "u8 empty_function { return 0; }"

Can it work
What do you think about it?

Fabio
> 
> julia