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From:   "Fabio M. De Francesco" <fmdefrancesco@gmail.com>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Julia Lawall <julia.lawall@inria.fr>,
        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 22:08:32 +0200
Message-ID: <3505455.GpAHCVcAZI@linux.local>
In-Reply-To: <20210413194844.GR2531743@casper.infradead.org>
References: <20210413155908.8691-1-fmdefrancesco@gmail.com> <7008359.Jy8utYDuns@linux.local> <20210413194844.GR2531743@casper.infradead.org>
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On Tuesday, April 13, 2021 9:48:44 PM CEST Matthew Wilcox wrote:
> On Tue, Apr 13, 2021 at 09:45:03PM +0200, Fabio M. De Francesco wrote:
> > 1) The driver doesn't call that function from anywhere else than the
> > macro. 2) You have explained that the macro add its symbol to a slot
> > in an array that would shift all the subsequent elements down if that
> > macro is not used exactly in the line where it is.
> > 3) Dan Carpenter said that that array is full of null functions (or
> > empty slots?).
> > 
> > Unless that function is called anonymously dereferencing its address
> > from the position it occupies in the array, I'm not able to see what
> > else means can any caller use.
> > 
> > I know I have much less experience than you with C: what can go wrong?
> 
> 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;
>
OK, I had imagined an anonymous call from its location in the array (as I 
wrote in the last phrase of my message). However, I thought that it could 
have been an improbable possibility, not a real one.

Linux uses a lot of interesting ideas that newcomers like me should learn. 
Things here are trickier than they appear at first sight.

Thanks,

Fabio