linux-kernel - Re: [PATCH] staging: rtl8188eu: Remove an unused variable and some lines of code

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Date:   Fri, 02 Jul 2021 14:14:45 +0200
From:   "Fabio M. De Francesco" <fmdefrancesco@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Larry Finger <Larry.Finger@...inger.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: rtl8188eu: Remove an unused variable and some lines of code

On Friday, July 2, 2021 10:35:21 AM CEST Dan Carpenter wrote:
> On Fri, Jul 02, 2021 at 10:48:40AM +0300, Dan Carpenter wrote:
> > On Thu, Jul 01, 2021 at 04:47:07PM +0200, Fabio M. De Francesco wrote:
> > > Remove set but unused iw_operation_mode[]. Remove all the lines of
> > > code from the function rtw_wx_set_rate, except the "return 0;" line
> > > to not break userland code that somewhat uses this IOCTL.
> > > 
> > > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
> > > [...]
> > 

Dear Dan,

> > Just delete this whole file.  It doesn't do anything now.
> 
> Sorry, I meant function, not file.  *chortle*.  :P

No worries, it is clear it was unintended.

Back to the function... As you may suspect :-) I know practically nothing 
neither of Linux device drivers or of whatever else kernel, so I take your 
words for good. ASAP, I'll send a v2 of this patch.

However, I usually like to understand what I make (just for fun and... more).

That rtw_wx_set_rate() is the implementation of the SIOCSIWRATE IOCTL command. 
I hope that I have not misunderstood it, have I? 

However, we know that this function does practically nothing and then simply 
returns 0 to the user. That's exactly the reason why I deleted all its lines 
(except one). 

If I am a user of that command I get a "success" return code (0) and I don't  
notice that it won't be able to set the bit rate. However everything should 
still keep running (I suppose using the default bit rate of the hardware; who 
really knows?). 

Now it's time for two questions: 

1) what happens if that command is used by some users that (hopelessly) expect 
the function to set the bit rate? I mean: if the function is not anymore in 
the list of the IOCTL commands of the rtw_handlers array will still the user 
program compile, link, and don't crash at runtime? 

2) how should I delete the association of SIOCSIWRATE with rtw_wx_set_rate() 
in the rtw_handlers array?
	- delete the entry and shift the array one position up?
	- set the SIOCSIWRATE entry to NULL?

Regards,

Fabio
> 
> regards,
> dan carpenter