netdev - Re: [PATCH 2/3][V2] rtlwifi: rtl8192de: make arrays static const, makes object smaller

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Date:   Tue, 03 Aug 2021 08:23:51 -0700
From:   Joe Perches <joe@...ches.com>
To:     Colin Ian King <colin.king@...onical.com>,
        Ping-Ke Shih <pkshih@...ltek.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3][V2] rtlwifi: rtl8192de: make arrays static const,
 makes object smaller

On Tue, 2021-08-03 at 16:15 +0100, Colin Ian King wrote:
> On 03/08/2021 16:09, Joe Perches wrote:
> > On Tue, 2021-08-03 at 15:49 +0100, Colin King wrote:
> > > Don't populate arrays the stack but instead make them static const. Replace
> > > array channel_info with channel_all since it contains the same data as
> > > channel_all. Makes object code smaller by 961 bytes.
> > []
> > > diff --git a/drivers/net/wireless/realtek/rtlwifi/rtl8192de/phy.c b/drivers/net/wireless/realtek/rtlwifi/rtl8192de/phy.c
> > []
> > > @@ -160,6 +160,15 @@ static u32 targetchnl_2g[TARGET_CHNL_NUM_2G] = {
> > >  	25711, 25658, 25606, 25554, 25502, 25451, 25328
> > >  };
> > > 
> > > +static const u8 channel_all[59] = {
> > 
> > I don't believe there is a significant value in sizing the array
> > as 59 instead of letting the compiler count the elements.
> 
> I was reluctant to remove this as I supposed the original had it in for
> a purpose, e.g. to ensure that the array was not populated with more
> data than intended. Does it make much of a difference?
> 
> > 
> > > +	1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
> > > +	36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58,
> > > +	60, 62, 64, 100, 102, 104, 106, 108, 110, 112,
> > > +	114, 116, 118, 120, 122, 124, 126, 128,	130,
> > > +	132, 134, 136, 138, 140, 149, 151, 153, 155,
> > > +	157, 159, 161, 163, 165
> > > +};

Dunno.

Maybe not, but I did have to count the elements to see if
it really was 59 or the compiler was adding trailing 0's.

OK I really did a grep to count the commas and added 1...