linux-kernel - [PATCH] wifi: rt2x00: use explicitly signed type for clamping

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Date:   Tue, 18 Oct 2022 14:27:34 -0600
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Stanislaw Gruszka <stf_xl@...pl>,
        Helmut Schaa <helmut.schaa@...glemail.com>,
        Kalle Valo <kvalo@...nel.org>
Subject: [PATCH] wifi: rt2x00: use explicitly signed type for clamping

On some platforms, `char` is unsigned, which makes casting -7 to char
overflow, which in turn makes the clamping operation bogus. Instead,
deal with an explicit `s8` type, so that the comparison is always
signed, and return an s8 result from the function as well. Note that
this function's result is assigned to a `short`, which is always signed.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Stanislaw Gruszka <stf_xl@...pl>
Cc: Helmut Schaa <helmut.schaa@...glemail.com>
Cc: Kalle Valo <kvalo@...nel.org>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 drivers/net/wireless/ralink/rt2x00/rt2800lib.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/net/wireless/ralink/rt2x00/rt2800lib.c b/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
index cbbb1a4849cf..e233ef9892b3 100644
--- a/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
+++ b/drivers/net/wireless/ralink/rt2x00/rt2800lib.c
@@ -4035,23 +4035,23 @@ static void rt2800_iq_calibrate(struct rt2x00_dev *rt2x00dev, int channel)
 	rt2800_bbp_write(rt2x00dev, 159, cal != 0xff ? cal : 0);
 }
 
-static char rt2800_txpower_to_dev(struct rt2x00_dev *rt2x00dev,
+static s8 rt2800_txpower_to_dev(struct rt2x00_dev *rt2x00dev,
 				  unsigned int channel,
-				  char txpower)
+				  s8 txpower)
 {
 	if (rt2x00_rt(rt2x00dev, RT3593) ||
 	    rt2x00_rt(rt2x00dev, RT3883))
 		txpower = rt2x00_get_field8(txpower, EEPROM_TXPOWER_ALC);
 
 	if (channel <= 14)
-		return clamp_t(char, txpower, MIN_G_TXPOWER, MAX_G_TXPOWER);
+		return clamp_t(s8, txpower, MIN_G_TXPOWER, MAX_G_TXPOWER);
 
 	if (rt2x00_rt(rt2x00dev, RT3593) ||
 	    rt2x00_rt(rt2x00dev, RT3883))
-		return clamp_t(char, txpower, MIN_A_TXPOWER_3593,
+		return clamp_t(s8, txpower, MIN_A_TXPOWER_3593,
 			       MAX_A_TXPOWER_3593);
 	else
-		return clamp_t(char, txpower, MIN_A_TXPOWER, MAX_A_TXPOWER);
+		return clamp_t(s8, txpower, MIN_A_TXPOWER, MAX_A_TXPOWER);
 }
 
 static void rt3883_bbp_adjust(struct rt2x00_dev *rt2x00dev,
-- 
2.37.3