linux-kernel - Re: [Outreachy kernel] [PATCH] staging: rtl8723bs: Remove useless led_blink

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Date:   Wed, 14 Apr 2021 15:27:03 +0200
From:   "Fabio M. De Francesco" <fmdefrancesco@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     outreachy-kernel@...glegroups.com, linux-staging@...ts.linux.dev,
        linux-kernel@...r.kernel.org, Matthew Wilcox <willy@...radead.org>,
        Julia Lawall <julia.lawall@...ia.fr>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [Outreachy kernel] [PATCH] staging: rtl8723bs: Remove useless led_blink_hdl()

On Wednesday, April 14, 2021 2:18:13 PM CEST Greg Kroah-Hartman wrote:
> On Wed, Apr 14, 2021 at 01:52:43PM +0200, Fabio M. De Francesco wrote:
> > Removed the led_blink_hdl() function (declaration and definition).
> > Declared dummy_function() in include/rtw_mlme_ext.h and defined it in
> > core/rtw_cmd.c. Changed the second parameter of GEN_MLME_EXT_HANDLER
> > macro to make use of dummy_function().
> 
> No no no.
> 
> If you want to remove is function declaration and use, then do it
> properly.
> 
> The code is crazy, I agree, but it should not be difficult to just
> remove this correctly instead of papering over this mess.
> 
> Also note that no one actually calls this function if you look at the
> logic here.  
>
> It might take some good knowledge of C to unwind this crud,
> but once done, you should be able to "prove" it's not called
>
Proving that no one actually calls it it's beyond my 
current knowledge of programming with C.

Matthew W., who is for sure more experienced than I am , 
wrote that that function pointer in the array is used somewhere else. 

Copied and pasted here from his message:

"Here's where the driver calls that function:
$ git grep wlancmds drivers/staging/rtl8723bs/
drivers/staging/rtl8723bs/core/rtw_cmd.c:static struct cmd_hdl wlancmds[] = {
drivers/staging/rtl8723bs/core/rtw_cmd.c:               if (pcmd->cmdcode < ARRAY_SIZE(wlancmds)) {
drivers/staging/rtl8723bs/core/rtw_cmd.c:                       cmd_hdl = wlancmds[pcmd->cmdcode].h2cfuns;
>
> and how to
> remove it correctly.
>
I think that doing it correctly depends on the "prove" which you requested.
Doesn't it?
> 
> And no, I'm not going to say how to do it, that's an exercise best left
> for the reader.
>
It sounds perfectly reasonable and I agree in full.
>
> But I will hint that this was done in the past, in
> 2014, in another driver in the tree with a codebase much like this one,
> so it shouldn't be hard to find an example of it.  Only took me a few
> minutes...
>
I'm sure it took you only a few minutes. If this can be accomplished by using grep 
on git log output I need some time to read this command manual again. I suppose 
that the search should be made by combining "remove", "function", "drivers/staging",
and "2014". At the moment I don't know how to do that.

Notwithstanding I have said all that you read above, you can be sure that I won't give
up so easily even if it will take days :) 
> 
> good luck!
>
Thanks, 

Fabio
> 
> greg k-h