linux-kernel - Re: [PATCH] [v2] iwlegacy: don't warn for unused variables with DEBUG

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Message-Id: <7e472cbe-bf29-432b-93da-d1fc87630939@app.fastmail.com>
Date: Sat, 01 Mar 2025 14:49:38 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "Stanislaw Gruszka" <stf_xl@...pl>
Cc: "Arnd Bergmann" <arnd@...nel.org>,
 "Johannes Berg" <johannes@...solutions.net>, "Kalle Valo" <kvalo@...nel.org>,
 "Ben Hutchings" <ben@...adent.org.uk>, linux <linux@...blig.org>,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [v2] iwlegacy: don't warn for unused variables with DEBUG_FS=n

On Sat, Mar 1, 2025, at 14:36, Stanislaw Gruszka wrote:
> On Sat, Mar 01, 2025 at 01:38:16PM +0100, Arnd Bergmann wrote:
>> On Sat, Mar 1, 2025, at 13:28, Stanislaw Gruszka wrote:
>> > On Tue, Feb 25, 2025 at 03:53:53PM +0100, Arnd Bergmann wrote:
>> >
>> > But then the code will be compiled for !CONFIG_MAC80211_DEBUGFS
>> > case, it does compile for me:
>> >
>> > -  22475	   1160	      0	  23635	   
>> > 5c53	drivers/net/wireless/intel/iwlegacy/4965-rs.o
>> > +  23008	   1168	      0	  24176	   
>> > 5e70	drivers/net/wireless/intel/iwlegacy/4965-rs.o
>> 
>> Very strange, this really shouldn't happen. Which symbols
>> exactly do you see the compiler fail to drop with my patch,
>
> nm 4965-rs.o diffrence before and after patch:

>  00000000000000dd t il4965_rs_alloc_sta.cold
> -0000000000001810 t il4965_rs_collect_tx_data.isra.0
> -00000000000012b0 t il4965_rs_fill_link_cmd
> -0000000000000495 t il4965_rs_fill_link_cmd.cold
> +0000000000001850 t il4965_rs_collect_tx_data.isra.0
> +0000000000000e90 t il4965_rs_dbgfs_set_mcs.isra.0
> +00000000000002f6 t il4965_rs_dbgfs_set_mcs.isra.0.cold
> +0000000000001340 t il4965_rs_fill_link_cmd
> +0000000000000518 t il4965_rs_fill_link_cmd.cold
>  00000000000002a0 t il4965_rs_free

Ah, so the debugfs files get eliminated, but
il4965_rs_dbgfs_set_mcs() does not.

I think this should do it:

--- a/drivers/net/wireless/intel/iwlegacy/4965-rs.c
+++ b/drivers/net/wireless/intel/iwlegacy/4965-rs.c
@@ -2495,6 +2495,9 @@ il4965_rs_dbgfs_set_mcs(struct il_lq_sta *lq_sta, u32 * rate_n_flags, int idx)
        u8 valid_tx_ant;
        u8 ant_sel_tx;

+       if (!IS_ENABLED(CONFIG_MAC80211_DEBUGFS))
+               return;
+
        il = lq_sta->drv;
        valid_tx_ant = il->hw_params.valid_tx_ant;
        if (lq_sta->dbg_fixed_rate) {

or possibly il4965_rs_dbgfs_set_mcs() can stay in the #ifdef
if you prefer.

      Arnd