bitops: Provide generic sign_extend32 function

This patch moves code out from wireless drivers where two different
functions are defined in three code locations for the same purpose and
provides a common function to sign extend a 32-bit value.

Signed-off-by: Andreas Herrmann <[e-mail]>
Signed-off-by: John W. Linville <[e-mail]>

drivers/net/wireless/ath/ath5k/phy.c

···
   PHY calibration
 \*****************/
 
-static int sign_extend(int val, const int nbits)
-{
-	int order = BIT(nbits-1);
-	return (val ^ order) - order;
-}
-
 static s32 ath5k_hw_read_measured_noise_floor(struct ath5k_hw *ah)
 {
 	s32 val;
 
 	val = ath5k_hw_reg_read(ah, AR5K_PHY_NF);
-	return sign_extend(AR5K_REG_MS(val, AR5K_PHY_NF_MINCCA_PWR), 9);
+	return sign_extend32(AR5K_REG_MS(val, AR5K_PHY_NF_MINCCA_PWR), 8);
 }
 
 void ath5k_hw_init_nfcal_hist(struct ath5k_hw *ah)

drivers/net/wireless/ath/ath9k/ar5008_phy.c

···
 	int16_t nf;
 
 	nf = MS(REG_READ(ah, AR_PHY_CCA), AR_PHY_MINCCA_PWR);
-	nfarray[0] = sign_extend(nf, 9);
+	nfarray[0] = sign_extend32(nf, 8);
 
 	nf = MS(REG_READ(ah, AR_PHY_CH1_CCA), AR_PHY_CH1_MINCCA_PWR);
-	nfarray[1] = sign_extend(nf, 9);
+	nfarray[1] = sign_extend32(nf, 8);
 
 	nf = MS(REG_READ(ah, AR_PHY_CH2_CCA), AR_PHY_CH2_MINCCA_PWR);
-	nfarray[2] = sign_extend(nf, 9);
+	nfarray[2] = sign_extend32(nf, 8);
 
 	if (!IS_CHAN_HT40(ah->curchan))
 		return;
 
 	nf = MS(REG_READ(ah, AR_PHY_EXT_CCA), AR_PHY_EXT_MINCCA_PWR);
-	nfarray[3] = sign_extend(nf, 9);
+	nfarray[3] = sign_extend32(nf, 8);
 
 	nf = MS(REG_READ(ah, AR_PHY_CH1_EXT_CCA), AR_PHY_CH1_EXT_MINCCA_PWR);
-	nfarray[4] = sign_extend(nf, 9);
+	nfarray[4] = sign_extend32(nf, 8);
 
 	nf = MS(REG_READ(ah, AR_PHY_CH2_EXT_CCA), AR_PHY_CH2_EXT_MINCCA_PWR);
-	nfarray[5] = sign_extend(nf, 9);
+	nfarray[5] = sign_extend32(nf, 8);
 }
 
 /*

drivers/net/wireless/ath/ath9k/ar9002_phy.c

···
 	int16_t nf;
 
 	nf = MS(REG_READ(ah, AR_PHY_CCA), AR9280_PHY_MINCCA_PWR);
-	nfarray[0] = sign_extend(nf, 9);
+	nfarray[0] = sign_extend32(nf, 8);
 
 	nf = MS(REG_READ(ah, AR_PHY_EXT_CCA), AR9280_PHY_EXT_MINCCA_PWR);
 	if (IS_CHAN_HT40(ah->curchan))
-		nfarray[3] = sign_extend(nf, 9);
+		nfarray[3] = sign_extend32(nf, 8);
 
 	if (AR_SREV_9285(ah) || AR_SREV_9271(ah))
 		return;
 
 	nf = MS(REG_READ(ah, AR_PHY_CH1_CCA), AR9280_PHY_CH1_MINCCA_PWR);
-	nfarray[1] = sign_extend(nf, 9);
+	nfarray[1] = sign_extend32(nf, 8);
 
 	nf = MS(REG_READ(ah, AR_PHY_CH1_EXT_CCA), AR9280_PHY_CH1_EXT_MINCCA_PWR);
 	if (IS_CHAN_HT40(ah->curchan))
-		nfarray[4] = sign_extend(nf, 9);
+		nfarray[4] = sign_extend32(nf, 8);
 }
 
 static void ar9002_hw_set_nf_limits(struct ath_hw *ah)

drivers/net/wireless/ath/ath9k/ar9003_phy.c

···
 	int16_t nf;
 
 	nf = MS(REG_READ(ah, AR_PHY_CCA_0), AR_PHY_MINCCA_PWR);
-	nfarray[0] = sign_extend(nf, 9);
+	nfarray[0] = sign_extend32(nf, 8);
 
 	nf = MS(REG_READ(ah, AR_PHY_CCA_1), AR_PHY_CH1_MINCCA_PWR);
-	nfarray[1] = sign_extend(nf, 9);
+	nfarray[1] = sign_extend32(nf, 8);
 
 	nf = MS(REG_READ(ah, AR_PHY_CCA_2), AR_PHY_CH2_MINCCA_PWR);
-	nfarray[2] = sign_extend(nf, 9);
+	nfarray[2] = sign_extend32(nf, 8);
 
 	if (!IS_CHAN_HT40(ah->curchan))
 		return;
 
 	nf = MS(REG_READ(ah, AR_PHY_EXT_CCA), AR_PHY_EXT_MINCCA_PWR);
-	nfarray[3] = sign_extend(nf, 9);
+	nfarray[3] = sign_extend32(nf, 8);
 
 	nf = MS(REG_READ(ah, AR_PHY_EXT_CCA_1), AR_PHY_CH1_EXT_MINCCA_PWR);
-	nfarray[4] = sign_extend(nf, 9);
+	nfarray[4] = sign_extend32(nf, 8);
 
 	nf = MS(REG_READ(ah, AR_PHY_EXT_CCA_2), AR_PHY_CH2_EXT_MINCCA_PWR);
-	nfarray[5] = sign_extend(nf, 9);
+	nfarray[5] = sign_extend32(nf, 8);
 }
 
 static void ar9003_hw_set_nf_limits(struct ath_hw *ah)

drivers/net/wireless/ath/ath9k/hw.h

···
 	return &ah->ops;
 }
 
-static inline int sign_extend(int val, const int nbits)
-{
-	int order = BIT(nbits-1);
-	return (val ^ order) - order;
-}
-
 /* Initialization, Detach, Reset */
 const char *ath9k_hw_probe(u16 vendorid, u16 devid);
 void ath9k_hw_deinit(struct ath_hw *ah);

drivers/net/wireless/iwlwifi/iwl-4965.c

···
 }
 
 /**
- * sign_extend - Sign extend a value using specified bit as sign-bit
- *
- * Example: sign_extend(9, 3) would return -7 as bit3 of 1001b is 1
- * and bit0..2 is 001b which when sign extended to 1111111111111001b is -7.
- *
- * @param oper value to sign extend
- * @param index 0 based bit index (0<=index<32) to sign bit
- */
-static s32 sign_extend(u32 oper, int index)
-{
-	u8 shift = 31 - index;
-
-	return (s32)(oper << shift) >> shift;
-}
-
-/**
  * iwl4965_hw_get_temperature - return the calibrated temperature (in Kelvin)
  * @statistics: Provides the temperature reading from the uCode
  *
···
 	 * "initialize" ALIVE response.
 	 */
 	if (!test_bit(STATUS_TEMPERATURE, &priv->status))
-		vt = sign_extend(R4, 23);
+		vt = sign_extend32(R4, 23);
 	else
-		vt = sign_extend(le32_to_cpu(priv->_agn.statistics.
+		vt = sign_extend32(le32_to_cpu(priv->_agn.statistics.
 				 general.common.temperature), 23);
 
 	IWL_DEBUG_TEMP(priv, "Calib values R[1-3]: %d %d %d R4: %d\n", R1, R2, R3, vt);

include/linux/bitops.h

···
 	return (word >> shift) | (word << (8 - shift));
 }
 
+/**
+ * sign_extend32 - sign extend a 32-bit value using specified bit as sign-bit
+ * @value: value to sign extend
+ * @index: 0 based bit index (0<=index<32) to sign bit
+ */
+static inline __s32 sign_extend32(__u32 value, int index)
+{
+	__u8 shift = 31 - index;
+	return (__s32)(value << shift) >> shift;
+}
+
 static inline unsigned fls_long(unsigned long l)
 {
 	if (sizeof(l) == 4)