staging: r8188eu: add error handling of rtw_read8

rtw_read8() reads data from device via USB API which may fail. In case
of any failure previous code returned stack data to callers, which is
wrong.

Fix it by changing rtw_read8() prototype and prevent caller from
touching random stack data
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Link: https://lore.kernel.org/r/c8f8ef4f14db3ba2478a87d5be6eb768a093dfaf.1654629778.git.paskripkin@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/r8188eu/core/rtw_efuse.c

@@ -28,14 +28,21 @@ ReadEFuseByte(
 	u32 value32;
 	u8 readbyte;
 	u16 retry;
+	int res;
 
 	/* Write Address */
 	rtw_write8(Adapter, EFUSE_CTRL + 1, (_offset & 0xff));
-	readbyte = rtw_read8(Adapter, EFUSE_CTRL + 2);
+	res = rtw_read8(Adapter, EFUSE_CTRL + 2, &readbyte);
+	if (res)
+		return;
+
 	rtw_write8(Adapter, EFUSE_CTRL + 2, ((_offset >> 8) & 0x03) | (readbyte & 0xfc));
 
 	/* Write bit 32 0 */
-	readbyte = rtw_read8(Adapter, EFUSE_CTRL + 3);
+	res = rtw_read8(Adapter, EFUSE_CTRL + 3, &readbyte);
+	if (res)
+		return;
+
 	rtw_write8(Adapter, EFUSE_CTRL + 3, (readbyte & 0x7f));
 
 	/* Check bit 32 read-ready */
@@ -54,6 +61,8 @@ ReadEFuseByte(
 	value32 = rtw_read32(Adapter, EFUSE_CTRL);
 
 	*pbuf = (u8)(value32 & 0xff);
+
+	/* FIXME: return an error to caller */
 }
 
 /*-----------------------------------------------------------------------------

drivers/staging/r8188eu/core/rtw_fw.c

@@ -44,18 +44,28 @@ static_assert(sizeof(struct rt_firmware_hdr) == 32);
 static void fw_download_enable(struct adapter *padapter, bool enable)
 {
 	u8 tmp;
+	int res;
 
 	if (enable) {
 		/*  MCU firmware download enable. */
-		tmp = rtw_read8(padapter, REG_MCUFWDL);
+		res = rtw_read8(padapter, REG_MCUFWDL, &tmp);
+		if (res)
+			return;
+
 		rtw_write8(padapter, REG_MCUFWDL, tmp | 0x01);
 
 		/*  8051 reset */
-		tmp = rtw_read8(padapter, REG_MCUFWDL + 2);
+		res = rtw_read8(padapter, REG_MCUFWDL + 2, &tmp);
+		if (res)
+			return;
+
 		rtw_write8(padapter, REG_MCUFWDL + 2, tmp & 0xf7);
 	} else {
 		/*  MCU firmware download disable. */
-		tmp = rtw_read8(padapter, REG_MCUFWDL);
+		res = rtw_read8(padapter, REG_MCUFWDL, &tmp);
+		if (res)
+			return;
+
 		rtw_write8(padapter, REG_MCUFWDL, tmp & 0xfe);
 
 		/*  Reserved for fw extension. */
@@ -125,8 +135,13 @@ static int page_write(struct adapter *padapter, u32 page, u8 *buffer, u32 size)
 {
 	u8 value8;
 	u8 u8Page = (u8)(page & 0x07);
+	int res;
+
+	res = rtw_read8(padapter, REG_MCUFWDL + 2, &value8);
+	if (res)
+		return _FAIL;
 
-	value8 = (rtw_read8(padapter, REG_MCUFWDL + 2) & 0xF8) | u8Page;
+	value8 = (value8 & 0xF8) | u8Page;
 	rtw_write8(padapter, REG_MCUFWDL + 2, value8);
 
 	return block_write(padapter, buffer, size);
@@ -165,8 +180,12 @@ static int write_fw(struct adapter *padapter, u8 *buffer, u32 size)
 void rtw_reset_8051(struct adapter *padapter)
 {
 	u8 val8;
+	int res;
+
+	res = rtw_read8(padapter, REG_SYS_FUNC_EN + 1, &val8);
+	if (res)
+		return;
 
-	val8 = rtw_read8(padapter, REG_SYS_FUNC_EN + 1);
 	rtw_write8(padapter, REG_SYS_FUNC_EN + 1, val8 & (~BIT(2)));
 	rtw_write8(padapter, REG_SYS_FUNC_EN + 1, val8 | (BIT(2)));
 }
@@ -239,7 +258,7 @@ static int load_firmware(struct rt_firmware *rtfw, struct device *device)
 int rtl8188e_firmware_download(struct adapter *padapter)
 {
 	int ret = _SUCCESS;
-	u8 write_fw_retry = 0;
+	u8 reg;
 	unsigned long fwdl_timeout;
 	struct dvobj_priv *dvobj = adapter_to_dvobj(padapter);
 	struct device *device = dvobj_to_dev(dvobj);
@@ -269,23 +288,34 @@ int rtl8188e_firmware_download(struct adapter *padapter)
 
 	/*  Suggested by Filen. If 8051 is running in RAM code, driver should inform Fw to reset by itself, */
 	/*  or it will cause download Fw fail. 2010.02.01. by tynli. */
-	if (rtw_read8(padapter, REG_MCUFWDL) & RAM_DL_SEL) { /* 8051 RAM code */
+	ret = rtw_read8(padapter, REG_MCUFWDL, &reg);
+	if (ret) {
+		ret = _FAIL;
+		goto exit;
+	}
+
+	if (reg & RAM_DL_SEL) { /* 8051 RAM code */
 		rtw_write8(padapter, REG_MCUFWDL, 0x00);
 		rtw_reset_8051(padapter);
 	}
 
 	fw_download_enable(padapter, true);
 	fwdl_timeout = jiffies + msecs_to_jiffies(500);
-	while (1) {
+	do {
 		/* reset the FWDL chksum */
-		rtw_write8(padapter, REG_MCUFWDL, rtw_read8(padapter, REG_MCUFWDL) | FWDL_CHKSUM_RPT);
+		ret = rtw_read8(padapter, REG_MCUFWDL, &reg);
+		if (ret) {
+			ret = _FAIL;
+			continue;
+		}
 
-		ret = write_fw(padapter, fw_data, fw_size);
+		rtw_write8(padapter, REG_MCUFWDL, reg | FWDL_CHKSUM_RPT);
 
-		if (ret == _SUCCESS ||
-		    (time_after(jiffies, fwdl_timeout) && write_fw_retry++ >= 3))
+		ret = write_fw(padapter, fw_data, fw_size);
+		if (ret == _SUCCESS)
 			break;
-	}
+	} while (!time_after(jiffies, fwdl_timeout));
+
 	fw_download_enable(padapter, false);
 	if (ret != _SUCCESS)
 		goto exit;

drivers/staging/r8188eu/core/rtw_led.c

@@ -35,11 +35,15 @@ static void ResetLedStatus(struct LED_871x *pLed)
 static void SwLedOn(struct adapter *padapter, struct LED_871x *pLed)
 {
 	u8	LedCfg;
+	int res;
 
 	if (padapter->bSurpriseRemoved || padapter->bDriverStopped)
 		return;
 
-	LedCfg = rtw_read8(padapter, REG_LEDCFG2);
+	res = rtw_read8(padapter, REG_LEDCFG2, &LedCfg);
+	if (res)
+		return;
+
 	rtw_write8(padapter, REG_LEDCFG2, (LedCfg & 0xf0) | BIT(5) | BIT(6)); /*  SW control led0 on. */
 	pLed->bLedOn = true;
 }
@@ -47,15 +51,21 @@ static void SwLedOn(struct adapter *padapter, struct LED_871x *pLed)
 static void SwLedOff(struct adapter *padapter, struct LED_871x *pLed)
 {
 	u8	LedCfg;
+	int res;
 
 	if (padapter->bSurpriseRemoved || padapter->bDriverStopped)
 		goto exit;
 
-	LedCfg = rtw_read8(padapter, REG_LEDCFG2);/* 0x4E */
+	res = rtw_read8(padapter, REG_LEDCFG2, &LedCfg);/* 0x4E */
+	if (res)
+		goto exit;
 
 	LedCfg &= 0x90; /*  Set to software control. */
 	rtw_write8(padapter, REG_LEDCFG2, (LedCfg | BIT(3)));
-	LedCfg = rtw_read8(padapter, REG_MAC_PINMUX_CFG);
+	res = rtw_read8(padapter, REG_MAC_PINMUX_CFG, &LedCfg);
+	if (res)
+		goto exit;
+
 	LedCfg &= 0xFE;
 	rtw_write8(padapter, REG_MAC_PINMUX_CFG, LedCfg);
 exit:

drivers/staging/r8188eu/core/rtw_mlme_ext.c

@@ -5650,14 +5650,28 @@ unsigned int send_beacon(struct adapter *padapter)
 
 bool get_beacon_valid_bit(struct adapter *adapter)
 {
+	int res;
+	u8 reg;
+
+	res = rtw_read8(adapter, REG_TDECTRL + 2, &reg);
+	if (res)
+		return false;
+
 	/* BIT(16) of REG_TDECTRL = BIT(0) of REG_TDECTRL+2 */
-	return BIT(0) & rtw_read8(adapter, REG_TDECTRL + 2);
+	return BIT(0) & reg;
 }
 
 void clear_beacon_valid_bit(struct adapter *adapter)
 {
+	int res;
+	u8 reg;
+
+	res = rtw_read8(adapter, REG_TDECTRL + 2, &reg);
+	if (res)
+		return;
+
 	/* BIT(16) of REG_TDECTRL = BIT(0) of REG_TDECTRL+2, write 1 to clear, Clear by sw */
-	rtw_write8(adapter, REG_TDECTRL + 2, rtw_read8(adapter, REG_TDECTRL + 2) | BIT(0));
+	rtw_write8(adapter, REG_TDECTRL + 2, reg | BIT(0));
 }
 
 /****************************************************************************
@@ -5985,7 +5999,8 @@ static void rtw_set_bssid(struct adapter *adapter, u8 *bssid)
 static void mlme_join(struct adapter *adapter, int type)
 {
 	struct mlme_priv *mlmepriv = &adapter->mlmepriv;
-	u8 retry_limit = 0x30;
+	u8 retry_limit = 0x30, reg;
+	int res;
 
 	switch (type) {
 	case 0:
@@ -6010,7 +6025,11 @@ static void mlme_join(struct adapter *adapter, int type)
 	case 2:
 		/* sta add event call back */
 		/* enable update TSF */
-		rtw_write8(adapter, REG_BCN_CTRL, rtw_read8(adapter, REG_BCN_CTRL) & (~BIT(4)));
+		res = rtw_read8(adapter, REG_BCN_CTRL, &reg);
+		if (res)
+			return;
+
+		rtw_write8(adapter, REG_BCN_CTRL, reg & (~BIT(4)));
 
 		if (check_fwstate(mlmepriv, WIFI_ADHOC_STATE | WIFI_ADHOC_MASTER_STATE))
 			retry_limit = 0x7;
@@ -6731,6 +6750,9 @@ void mlmeext_sta_add_event_callback(struct adapter *padapter, struct sta_info *p
 
 static void mlme_disconnect(struct adapter *adapter)
 {
+	int res;
+	u8 reg;
+
 	/* Set RCR to not to receive data frame when NO LINK state */
 	/* reject all data frames */
 	rtw_write16(adapter, REG_RXFLTMAP2, 0x00);
@@ -6739,7 +6761,12 @@ static void mlme_disconnect(struct adapter *adapter)
 	rtw_write8(adapter, REG_DUAL_TSF_RST, (BIT(0) | BIT(1)));
 
 	/* disable update TSF */
-	rtw_write8(adapter, REG_BCN_CTRL, rtw_read8(adapter, REG_BCN_CTRL) | BIT(4));
+
+	res = rtw_read8(adapter, REG_BCN_CTRL, &reg);
+	if (res)
+		return;
+
+	rtw_write8(adapter, REG_BCN_CTRL, reg | BIT(4));
 }
 
 void mlmeext_sta_del_event_callback(struct adapter *padapter)
@@ -6793,14 +6820,15 @@ static u8 chk_ap_is_alive(struct sta_info *psta)
 	return ret;
 }
 
-static void rtl8188e_sreset_linked_status_check(struct adapter *padapter)
+static int rtl8188e_sreset_linked_status_check(struct adapter *padapter)
 {
 	u32 rx_dma_status =  rtw_read32(padapter, REG_RXDMA_STATUS);
+	u8 reg;
 
 	if (rx_dma_status != 0x00)
 		rtw_write32(padapter, REG_RXDMA_STATUS, rx_dma_status);
 
-	rtw_read8(padapter, REG_FMETHR);
+	return rtw_read8(padapter, REG_FMETHR, &reg);
 }
 
 void linked_status_chk(struct adapter *padapter)
@@ -7202,6 +7230,7 @@ u8 disconnect_hdl(struct adapter *padapter, unsigned char *pbuf)
 	struct mlme_ext_info	*pmlmeinfo = &pmlmeext->mlmext_info;
 	struct wlan_bssid_ex *pnetwork = (struct wlan_bssid_ex *)(&pmlmeinfo->network);
 	u8 val8;
+	int res;
 
 	if (is_client_associated_to_ap(padapter))
 		issue_deauth_ex(padapter, pnetwork->MacAddress, WLAN_REASON_DEAUTH_LEAVING, param->deauth_timeout_ms / 100, 100);
@@ -7214,7 +7243,10 @@ u8 disconnect_hdl(struct adapter *padapter, unsigned char *pbuf)
 
 	if (((pmlmeinfo->state & 0x03) == WIFI_FW_ADHOC_STATE) || ((pmlmeinfo->state & 0x03) == WIFI_FW_AP_STATE)) {
 		/* Stop BCN */
-		val8 = rtw_read8(padapter, REG_BCN_CTRL);
+		res = rtw_read8(padapter, REG_BCN_CTRL, &val8);
+		if (res)
+			return H2C_DROPPED;
+
 		rtw_write8(padapter, REG_BCN_CTRL, val8 & (~(EN_BCN_FUNCTION | EN_TXBCN_RPT)));
 	}
 

drivers/staging/r8188eu/core/rtw_wlan_util.c

@@ -279,8 +279,13 @@ void Restore_DM_Func_Flag(struct adapter *padapter)
 void Set_MSR(struct adapter *padapter, u8 type)
 {
 	u8 val8;
+	int res;
 
-	val8 = rtw_read8(padapter, MSR) & 0x0c;
+	res = rtw_read8(padapter, MSR, &val8);
+	if (res)
+		return;
+
+	val8 &= 0x0c;
 	val8 |= type;
 	rtw_write8(padapter, MSR, val8);
 }
@@ -505,7 +510,11 @@ int WMM_param_handler(struct adapter *padapter, struct ndis_802_11_var_ie *pIE)
 
 static void set_acm_ctrl(struct adapter *adapter, u8 acm_mask)
 {
-	u8 acmctrl = rtw_read8(adapter, REG_ACMHWCTRL);
+	u8 acmctrl;
+	int res = rtw_read8(adapter, REG_ACMHWCTRL, &acmctrl);
+
+	if (res)
+		return;
 
 	if (acm_mask > 1)
 		acmctrl = acmctrl | 0x1;
@@ -765,6 +774,7 @@ void HT_info_handler(struct adapter *padapter, struct ndis_802_11_var_ie *pIE)
 static void set_min_ampdu_spacing(struct adapter *adapter, u8 spacing)
 {
 	u8 sec_spacing;
+	int res;
 
 	if (spacing <= 7) {
 		switch (adapter->securitypriv.dot11PrivacyAlgrthm) {
@@ -786,8 +796,12 @@ static void set_min_ampdu_spacing(struct adapter *adapter, u8 spacing)
 		if (spacing < sec_spacing)
 			spacing = sec_spacing;
 
+		res = rtw_read8(adapter, REG_AMPDU_MIN_SPACE, &sec_spacing);
+		if (res)
+			return;
+
 		rtw_write8(adapter, REG_AMPDU_MIN_SPACE,
-			   (rtw_read8(adapter, REG_AMPDU_MIN_SPACE) & 0xf8) | spacing);
+			   (sec_spacing & 0xf8) | spacing);
 	}
 }
 

drivers/staging/r8188eu/hal/HalPhyRf_8188e.c

@@ -463,6 +463,7 @@ void _PHY_SaveADDARegisters(struct adapter *adapt, u32 *ADDAReg, u32 *ADDABackup
 	}
 }
 
+/* FIXME: return an error to caller */
 static void _PHY_SaveMACRegisters(
 		struct adapter *adapt,
 		u32 *MACReg,
@@ -470,9 +471,17 @@ static void _PHY_SaveMACRegisters(
 	)
 {
 	u32 i;
+	int res;
 
-	for (i = 0; i < (IQK_MAC_REG_NUM - 1); i++)
-		MACBackup[i] = rtw_read8(adapt, MACReg[i]);
+	for (i = 0; i < (IQK_MAC_REG_NUM - 1); i++) {
+		u8 reg;
+
+		res = rtw_read8(adapt, MACReg[i], &reg);
+		if (res)
+			return;
+
+		MACBackup[i] = reg;
+	}
 
 	MACBackup[i] = rtw_read32(adapt, MACReg[i]);
 }
@@ -739,9 +748,12 @@ static void phy_LCCalibrate_8188E(struct adapter *adapt)
 {
 	u8 tmpreg;
 	u32 RF_Amode = 0, LC_Cal;
+	int res;
 
 	/* Check continuous TX and Packet TX */
-	tmpreg = rtw_read8(adapt, 0xd03);
+	res = rtw_read8(adapt, 0xd03, &tmpreg);
+	if (res)
+		return;
 
 	if ((tmpreg & 0x70) != 0)			/* Deal with contisuous TX case */
 		rtw_write8(adapt, 0xd03, tmpreg & 0x8F);	/* disable all continuous TX */

drivers/staging/r8188eu/hal/HalPwrSeqCmd.c

@@ -12,6 +12,7 @@ u8 HalPwrSeqCmdParsing(struct adapter *padapter, struct wl_pwr_cfg pwrseqcmd[])
 	u32 offset = 0;
 	u32 poll_count = 0; /*  polling autoload done. */
 	u32 max_poll_count = 5000;
+	int res;
 
 	do {
 		pwrcfgcmd = pwrseqcmd[aryidx];
@@ -21,7 +22,9 @@ u8 HalPwrSeqCmdParsing(struct adapter *padapter, struct wl_pwr_cfg pwrseqcmd[])
 			offset = GET_PWR_CFG_OFFSET(pwrcfgcmd);
 
 			/*  Read the value from system register */
-			value = rtw_read8(padapter, offset);
+			res = rtw_read8(padapter, offset, &value);
+			if (res)
+				return false;
 
 			value &= ~(GET_PWR_CFG_MASK(pwrcfgcmd));
 			value |= (GET_PWR_CFG_VALUE(pwrcfgcmd) & GET_PWR_CFG_MASK(pwrcfgcmd));
@@ -33,7 +36,9 @@ u8 HalPwrSeqCmdParsing(struct adapter *padapter, struct wl_pwr_cfg pwrseqcmd[])
 			poll_bit = false;
 			offset = GET_PWR_CFG_OFFSET(pwrcfgcmd);
 			do {
-				value = rtw_read8(padapter, offset);
+				res = rtw_read8(padapter, offset, &value);
+				if (res)
+					return false;
 
 				value &= GET_PWR_CFG_MASK(pwrcfgcmd);
 				if (value == (GET_PWR_CFG_VALUE(pwrcfgcmd) & GET_PWR_CFG_MASK(pwrcfgcmd)))

drivers/staging/r8188eu/hal/hal_com.c

@@ -303,7 +303,9 @@ s32 c2h_evt_read(struct adapter *adapter, u8 *buf)
 	if (!buf)
 		goto exit;
 
-	trigger = rtw_read8(adapter, REG_C2HEVT_CLEAR);
+	ret = rtw_read8(adapter, REG_C2HEVT_CLEAR, &trigger);
+	if (ret)
+		return _FAIL;
 
 	if (trigger == C2H_EVT_HOST_CLOSE)
 		goto exit; /* Not ready */
@@ -314,13 +316,26 @@ s32 c2h_evt_read(struct adapter *adapter, u8 *buf)
 
 	memset(c2h_evt, 0, 16);
 
-	*buf = rtw_read8(adapter, REG_C2HEVT_MSG_NORMAL);
-	*(buf + 1) = rtw_read8(adapter, REG_C2HEVT_MSG_NORMAL + 1);
+	ret = rtw_read8(adapter, REG_C2HEVT_MSG_NORMAL, buf);
+	if (ret) {
+		ret = _FAIL;
+		goto clear_evt;
+	}
 
+	ret = rtw_read8(adapter, REG_C2HEVT_MSG_NORMAL + 1, buf + 1);
+	if (ret) {
+		ret = _FAIL;
+		goto clear_evt;
+	}
 	/* Read the content */
-	for (i = 0; i < c2h_evt->plen; i++)
-		c2h_evt->payload[i] = rtw_read8(adapter, REG_C2HEVT_MSG_NORMAL +
-						sizeof(*c2h_evt) + i);
+	for (i = 0; i < c2h_evt->plen; i++) {
+		ret = rtw_read8(adapter, REG_C2HEVT_MSG_NORMAL +
+						sizeof(*c2h_evt) + i, c2h_evt->payload + i);
+		if (ret) {
+			ret = _FAIL;
+			goto clear_evt;
+		}
+	}
 
 	ret = _SUCCESS;
 

drivers/staging/r8188eu/hal/rtl8188e_cmd.c

@@ -18,13 +18,18 @@
 
 static u8 _is_fw_read_cmd_down(struct adapter *adapt, u8 msgbox_num)
 {
-	u8 read_down = false;
+	u8 read_down = false, reg;
 	int	retry_cnts = 100;
+	int res;
 
 	u8 valid;
 
 	do {
-		valid = rtw_read8(adapt, REG_HMETFR) & BIT(msgbox_num);
+		res = rtw_read8(adapt, REG_HMETFR, &reg);
+		if (res)
+			continue;
+
+		valid = reg & BIT(msgbox_num);
 		if (0 == valid)
 			read_down = true;
 	} while ((!read_down) && (retry_cnts--));
@@ -533,6 +538,8 @@ void rtl8188e_set_FwJoinBssReport_cmd(struct adapter *adapt, u8 mstatus)
 	bool	bcn_valid = false;
 	u8 DLBcnCount = 0;
 	u32 poll = 0;
+	u8 reg;
+	int res;
 
 	if (mstatus == 1) {
 		/*  We should set AID, correct TSF, HW seq enable before set JoinBssReport to Fw in 88/92C. */
@@ -547,8 +554,17 @@ void rtl8188e_set_FwJoinBssReport_cmd(struct adapter *adapt, u8 mstatus)
 		/*  Disable Hw protection for a time which revserd for Hw sending beacon. */
 		/*  Fix download reserved page packet fail that access collision with the protection time. */
 		/*  2010.05.11. Added by tynli. */
-		rtw_write8(adapt, REG_BCN_CTRL, rtw_read8(adapt, REG_BCN_CTRL) & (~BIT(3)));
-		rtw_write8(adapt, REG_BCN_CTRL, rtw_read8(adapt, REG_BCN_CTRL) | BIT(4));
+		res = rtw_read8(adapt, REG_BCN_CTRL, &reg);
+		if (res)
+			return;
+
+		rtw_write8(adapt, REG_BCN_CTRL, reg & (~BIT(3)));
+
+		res = rtw_read8(adapt, REG_BCN_CTRL, &reg);
+		if (res)
+			return;
+
+		rtw_write8(adapt, REG_BCN_CTRL, reg | BIT(4));
 
 		if (haldata->RegFwHwTxQCtrl & BIT(6))
 			bSendBeacon = true;
@@ -581,8 +597,17 @@ void rtl8188e_set_FwJoinBssReport_cmd(struct adapter *adapt, u8 mstatus)
 		/*  */
 
 		/*  Enable Bcn */
-		rtw_write8(adapt, REG_BCN_CTRL, rtw_read8(adapt, REG_BCN_CTRL) | BIT(3));
-		rtw_write8(adapt, REG_BCN_CTRL, rtw_read8(adapt, REG_BCN_CTRL) & (~BIT(4)));
+		res = rtw_read8(adapt, REG_BCN_CTRL, &reg);
+		if (res)
+			return;
+
+		rtw_write8(adapt, REG_BCN_CTRL, reg | BIT(3));
+
+		res = rtw_read8(adapt, REG_BCN_CTRL, &reg);
+		if (res)
+			return;
+
+		rtw_write8(adapt, REG_BCN_CTRL, reg & (~BIT(4)));
 
 		/*  To make sure that if there exists an adapter which would like to send beacon. */
 		/*  If exists, the origianl value of 0x422[6] will be 1, we should check this to */

drivers/staging/r8188eu/hal/rtl8188e_dm.c

@@ -12,8 +12,12 @@
 static void dm_InitGPIOSetting(struct adapter *Adapter)
 {
 	u8	tmp1byte;
+	int res;
+
+	res = rtw_read8(Adapter, REG_GPIO_MUXCFG, &tmp1byte);
+	if (res)
+		return;
 
-	tmp1byte = rtw_read8(Adapter, REG_GPIO_MUXCFG);
 	tmp1byte &= (GPIOSEL_GPIO | ~GPIOSEL_ENBT);
 
 	rtw_write8(Adapter, REG_GPIO_MUXCFG, tmp1byte);

drivers/staging/r8188eu/hal/rtl8188e_hal_init.c

@@ -13,10 +13,14 @@
 static void iol_mode_enable(struct adapter *padapter, u8 enable)
 {
 	u8 reg_0xf0 = 0;
+	int res;
 
 	if (enable) {
 		/* Enable initial offload */
-		reg_0xf0 = rtw_read8(padapter, REG_SYS_CFG);
+		res = rtw_read8(padapter, REG_SYS_CFG, &reg_0xf0);
+		if (res)
+			return;
+
 		rtw_write8(padapter, REG_SYS_CFG, reg_0xf0 | SW_OFFLOAD_EN);
 
 		if (!padapter->bFWReady)
@@ -24,7 +28,10 @@ static void iol_mode_enable(struct adapter *padapter, u8 enable)
 
 	} else {
 		/* disable initial offload */
-		reg_0xf0 = rtw_read8(padapter, REG_SYS_CFG);
+		res = rtw_read8(padapter, REG_SYS_CFG, &reg_0xf0);
+		if (res)
+			return;
+
 		rtw_write8(padapter, REG_SYS_CFG, reg_0xf0 & ~SW_OFFLOAD_EN);
 	}
 }
@@ -34,17 +41,31 @@ static s32 iol_execute(struct adapter *padapter, u8 control)
 	s32 status = _FAIL;
 	u8 reg_0x88 = 0;
 	unsigned long timeout;
+	int res;
 
 	control = control & 0x0f;
-	reg_0x88 = rtw_read8(padapter, REG_HMEBOX_E0);
+	res = rtw_read8(padapter, REG_HMEBOX_E0, &reg_0x88);
+	if (res)
+		return _FAIL;
+
 	rtw_write8(padapter, REG_HMEBOX_E0,  reg_0x88 | control);
 
 	timeout = jiffies + msecs_to_jiffies(1000);
-	while ((reg_0x88 = rtw_read8(padapter, REG_HMEBOX_E0)) & control &&
-		time_before(jiffies, timeout))
-		;
 
-	reg_0x88 = rtw_read8(padapter, REG_HMEBOX_E0);
+	do {
+		res = rtw_read8(padapter, REG_HMEBOX_E0, &reg_0x88);
+		if (res)
+			continue;
+
+		if (!(reg_0x88 & control))
+			break;
+
+	} while (time_before(jiffies, timeout));
+
+	res = rtw_read8(padapter, REG_HMEBOX_E0, &reg_0x88);
+	if (res)
+		return _FAIL;
+
 	status = (reg_0x88 & control) ? _FAIL : _SUCCESS;
 	if (reg_0x88 & control << 4)
 		status = _FAIL;
@@ -190,13 +211,18 @@ static void efuse_read_phymap_from_txpktbuf(
 	u16 dbg_addr = 0;
 	__le32 lo32 = 0, hi32 = 0;
 	u16 len = 0, count = 0;
-	int i = 0;
+	int i = 0, res;
 	u16 limit = *size;
-
+	u8 reg;
 	u8 *pos = content;
 
-	if (bcnhead < 0) /* if not valid */
-		bcnhead = rtw_read8(adapter, REG_TDECTRL + 1);
+	if (bcnhead < 0) { /* if not valid */
+		res = rtw_read8(adapter, REG_TDECTRL + 1, &reg);
+		if (res)
+			return;
+
+		bcnhead = reg;
+	}
 
 	rtw_write8(adapter, REG_PKT_BUFF_ACCESS_CTRL, TXPKT_BUF_SELECT);
 
@@ -207,8 +233,16 @@ static void efuse_read_phymap_from_txpktbuf(
 
 		rtw_write8(adapter, REG_TXPKTBUF_DBG, 0);
 		timeout = jiffies + msecs_to_jiffies(1000);
-		while (!rtw_read8(adapter, REG_TXPKTBUF_DBG) && time_before(jiffies, timeout))
+		do {
+			res = rtw_read8(adapter, REG_TXPKTBUF_DBG, &reg);
+			if (res)
+				continue;
+
+			if (reg)
+				break;
+
 			rtw_usleep_os(100);
+		} while (time_before(jiffies, timeout));
 
 		/* data from EEPROM needs to be in LE */
 		lo32 = cpu_to_le32(rtw_read32(adapter, REG_PKTBUF_DBG_DATA_L));
@@ -525,10 +559,17 @@ void rtl8188e_SetHalODMVar(struct adapter *Adapter, void *pValue1, bool bSet)
 
 void hal_notch_filter_8188e(struct adapter *adapter, bool enable)
 {
+	int res;
+	u8 reg;
+
+	res = rtw_read8(adapter, rOFDM0_RxDSP + 1, &reg);
+	if (res)
+		return;
+
 	if (enable)
-		rtw_write8(adapter, rOFDM0_RxDSP + 1, rtw_read8(adapter, rOFDM0_RxDSP + 1) | BIT(1));
+		rtw_write8(adapter, rOFDM0_RxDSP + 1, reg | BIT(1));
 	else
-		rtw_write8(adapter, rOFDM0_RxDSP + 1, rtw_read8(adapter, rOFDM0_RxDSP + 1) & ~BIT(1));
+		rtw_write8(adapter, rOFDM0_RxDSP + 1, reg & ~BIT(1));
 }
 
 /*  */

drivers/staging/r8188eu/hal/rtl8188e_phycfg.c

@@ -594,6 +594,7 @@ _PHY_SetBWMode92C(
 	struct hal_data_8188e *pHalData = &Adapter->haldata;
 	u8 regBwOpMode;
 	u8 regRRSR_RSC;
+	int res;
 
 	if (Adapter->bDriverStopped)
 		return;
@@ -602,8 +603,13 @@ _PHY_SetBWMode92C(
 	/* 3<1>Set MAC register */
 	/* 3 */
 
-	regBwOpMode = rtw_read8(Adapter, REG_BWOPMODE);
-	regRRSR_RSC = rtw_read8(Adapter, REG_RRSR + 2);
+	res = rtw_read8(Adapter, REG_BWOPMODE, &regBwOpMode);
+	if (res)
+		return;
+
+	res = rtw_read8(Adapter, REG_RRSR + 2, &regRRSR_RSC);
+	if (res)
+		return;
 
 	switch (pHalData->CurrentChannelBW) {
 	case HT_CHANNEL_WIDTH_20:

drivers/staging/r8188eu/hal/usb_halinit.c

@@ -81,6 +81,7 @@ static void _InitInterrupt(struct adapter *Adapter)
 {
 	u32 imr, imr_ex;
 	u8  usb_opt;
+	int res;
 
 	/* HISR write one to clear */
 	rtw_write32(Adapter, REG_HISR_88E, 0xFFFFFFFF);
@@ -94,7 +95,9 @@ static void _InitInterrupt(struct adapter *Adapter)
 	/*  REG_USB_SPECIAL_OPTION - BIT(4) */
 	/*  0; Use interrupt endpoint to upload interrupt pkt */
 	/*  1; Use bulk endpoint to upload interrupt pkt, */
-	usb_opt = rtw_read8(Adapter, REG_USB_SPECIAL_OPTION);
+	res = rtw_read8(Adapter, REG_USB_SPECIAL_OPTION, &usb_opt);
+	if (res)
+		return;
 
 	if (adapter_to_dvobj(Adapter)->pusbdev->speed == USB_SPEED_HIGH)
 		usb_opt = usb_opt | (INT_BULK_SEL);
@@ -363,8 +366,12 @@ static void _InitEDCA(struct adapter *Adapter)
 static void _InitRetryFunction(struct adapter *Adapter)
 {
 	u8 value8;
+	int res;
+
+	res = rtw_read8(Adapter, REG_FWHW_TXQ_CTRL, &value8);
+	if (res)
+		return;
 
-	value8 = rtw_read8(Adapter, REG_FWHW_TXQ_CTRL);
 	value8 |= EN_AMPDU_RTY_NEW;
 	rtw_write8(Adapter, REG_FWHW_TXQ_CTRL, value8);
 
@@ -423,9 +430,15 @@ usb_AggSettingRxUpdate(
 {
 	u8 valueDMA;
 	u8 valueUSB;
+	int res;
 
-	valueDMA = rtw_read8(Adapter, REG_TRXDMA_CTRL);
-	valueUSB = rtw_read8(Adapter, REG_USB_SPECIAL_OPTION);
+	res = rtw_read8(Adapter, REG_TRXDMA_CTRL, &valueDMA);
+	if (res)
+		return;
+
+	res = rtw_read8(Adapter, REG_USB_SPECIAL_OPTION, &valueUSB);
+	if (res)
+		return;
 
 	valueDMA |= RXDMA_AGG_EN;
 	valueUSB &= ~USB_AGG_EN;
@@ -446,9 +459,11 @@ static void InitUsbAggregationSetting(struct adapter *Adapter)
 	usb_AggSettingRxUpdate(Adapter);
 }
 
-static void _InitBeaconParameters(struct adapter *Adapter)
+/* FIXME: add error handling in callers */
+static int _InitBeaconParameters(struct adapter *Adapter)
 {
 	struct hal_data_8188e *haldata = &Adapter->haldata;
+	int res;
 
 	rtw_write16(Adapter, REG_BCN_CTRL, 0x1010);
 
@@ -461,9 +476,19 @@ static void _InitBeaconParameters(struct adapter *Adapter)
 	/*  beacause test chip does not contension before sending beacon. by tynli. 2009.11.03 */
 	rtw_write16(Adapter, REG_BCNTCFG, 0x660F);
 
-	haldata->RegFwHwTxQCtrl = rtw_read8(Adapter, REG_FWHW_TXQ_CTRL + 2);
-	haldata->RegReg542 = rtw_read8(Adapter, REG_TBTT_PROHIBIT + 2);
-	haldata->RegCR_1 = rtw_read8(Adapter, REG_CR + 1);
+	res = rtw_read8(Adapter, REG_FWHW_TXQ_CTRL + 2, &haldata->RegFwHwTxQCtrl);
+	if (res)
+		return res;
+
+	res = rtw_read8(Adapter, REG_TBTT_PROHIBIT + 2, &haldata->RegReg542);
+	if (res)
+		return res;
+
+	res = rtw_read8(Adapter, REG_CR + 1, &haldata->RegCR_1);
+	if (res)
+		return res;
+
+	return 0;
 }
 
 static void _BeaconFunctionEnable(struct adapter *Adapter,
@@ -514,6 +539,7 @@ u32 rtl8188eu_hal_init(struct adapter *Adapter)
 	u16  value16;
 	u8 txpktbuf_bndy;
 	u32 status = _SUCCESS;
+	int res;
 	struct hal_data_8188e *haldata = &Adapter->haldata;
 	struct pwrctrl_priv		*pwrctrlpriv = &Adapter->pwrctrlpriv;
 	struct registry_priv	*pregistrypriv = &Adapter->registrypriv;
@@ -620,7 +646,10 @@ u32 rtl8188eu_hal_init(struct adapter *Adapter)
 
 	/* Enable TX Report */
 	/* Enable Tx Report Timer */
-	value8 = rtw_read8(Adapter, REG_TX_RPT_CTRL);
+	res = rtw_read8(Adapter, REG_TX_RPT_CTRL, &value8);
+	if (res)
+		return _FAIL;
+
 	rtw_write8(Adapter,  REG_TX_RPT_CTRL, (value8 | BIT(1) | BIT(0)));
 	/* Set MAX RPT MACID */
 	rtw_write8(Adapter,  REG_TX_RPT_CTRL + 1, 2);/* FOR sta mode ,0: bc/mc ,1:AP */
@@ -714,9 +743,13 @@ static void CardDisableRTL8188EU(struct adapter *Adapter)
 {
 	u8 val8;
 	struct hal_data_8188e *haldata = &Adapter->haldata;
+	int res;
 
 	/* Stop Tx Report Timer. 0x4EC[Bit1]=b'0 */
-	val8 = rtw_read8(Adapter, REG_TX_RPT_CTRL);
+	res = rtw_read8(Adapter, REG_TX_RPT_CTRL, &val8);
+	if (res)
+		return;
+
 	rtw_write8(Adapter, REG_TX_RPT_CTRL, val8 & (~BIT(1)));
 
 	/*  stop rx */
@@ -727,10 +760,16 @@ static void CardDisableRTL8188EU(struct adapter *Adapter)
 
 	/*  2. 0x1F[7:0] = 0		turn off RF */
 
-	val8 = rtw_read8(Adapter, REG_MCUFWDL);
+	res = rtw_read8(Adapter, REG_MCUFWDL, &val8);
+	if (res)
+		return;
+
 	if ((val8 & RAM_DL_SEL) && Adapter->bFWReady) { /* 8051 RAM code */
 		/*  Reset MCU 0x2[10]=0. */
-		val8 = rtw_read8(Adapter, REG_SYS_FUNC_EN + 1);
+		res = rtw_read8(Adapter, REG_SYS_FUNC_EN + 1, &val8);
+		if (res)
+			return;
+
 		val8 &= ~BIT(2);	/*  0x2[10], FEN_CPUEN */
 		rtw_write8(Adapter, REG_SYS_FUNC_EN + 1, val8);
 	}
@@ -740,26 +779,45 @@ static void CardDisableRTL8188EU(struct adapter *Adapter)
 
 	/* YJ,add,111212 */
 	/* Disable 32k */
-	val8 = rtw_read8(Adapter, REG_32K_CTRL);
+	res = rtw_read8(Adapter, REG_32K_CTRL, &val8);
+	if (res)
+		return;
+
 	rtw_write8(Adapter, REG_32K_CTRL, val8 & (~BIT(0)));
 
 	/*  Card disable power action flow */
 	HalPwrSeqCmdParsing(Adapter, Rtl8188E_NIC_DISABLE_FLOW);
 
 	/*  Reset MCU IO Wrapper */
-	val8 = rtw_read8(Adapter, REG_RSV_CTRL + 1);
+	res = rtw_read8(Adapter, REG_RSV_CTRL + 1, &val8);
+	if (res)
+		return;
+
 	rtw_write8(Adapter, REG_RSV_CTRL + 1, (val8 & (~BIT(3))));
-	val8 = rtw_read8(Adapter, REG_RSV_CTRL + 1);
+
+	res = rtw_read8(Adapter, REG_RSV_CTRL + 1, &val8);
+	if (res)
+		return;
+
 	rtw_write8(Adapter, REG_RSV_CTRL + 1, val8 | BIT(3));
 
 	/* YJ,test add, 111207. For Power Consumption. */
-	val8 = rtw_read8(Adapter, GPIO_IN);
+	res = rtw_read8(Adapter, GPIO_IN, &val8);
+	if (res)
+		return;
+
 	rtw_write8(Adapter, GPIO_OUT, val8);
 	rtw_write8(Adapter, GPIO_IO_SEL, 0xFF);/* Reg0x46 */
 
-	val8 = rtw_read8(Adapter, REG_GPIO_IO_SEL);
+	res = rtw_read8(Adapter, REG_GPIO_IO_SEL, &val8);
+	if (res)
+		return;
+
 	rtw_write8(Adapter, REG_GPIO_IO_SEL, (val8 << 4));
-	val8 = rtw_read8(Adapter, REG_GPIO_IO_SEL + 1);
+	res = rtw_read8(Adapter, REG_GPIO_IO_SEL + 1, &val8);
+	if (res)
+		return;
+
 	rtw_write8(Adapter, REG_GPIO_IO_SEL + 1, val8 | 0x0F);/* Reg0x43 */
 	rtw_write32(Adapter, REG_BB_PAD_CTRL, 0x00080808);/* set LNA ,TRSW,EX_PA Pin to output mode */
 	haldata->bMacPwrCtrlOn = false;
@@ -830,9 +888,13 @@ void ReadAdapterInfo8188EU(struct adapter *Adapter)
 	struct eeprom_priv *eeprom = &Adapter->eeprompriv;
 	struct led_priv *ledpriv = &Adapter->ledpriv;
 	u8 eeValue;
+	int res;
 
 	/* check system boot selection */
-	eeValue = rtw_read8(Adapter, REG_9346CR);
+	res = rtw_read8(Adapter, REG_9346CR, &eeValue);
+	if (res)
+		return;
+
 	eeprom->EepromOrEfuse		= (eeValue & BOOT_FROM_EEPROM);
 	eeprom->bautoload_fail_flag	= !(eeValue & EEPROM_EN);
 
@@ -887,12 +949,21 @@ static void hw_var_set_opmode(struct adapter *Adapter, u8 *val)
 {
 	u8 val8;
 	u8 mode = *((u8 *)val);
+	int res;
 
 	/*  disable Port0 TSF update */
-	rtw_write8(Adapter, REG_BCN_CTRL, rtw_read8(Adapter, REG_BCN_CTRL) | BIT(4));
+	res = rtw_read8(Adapter, REG_BCN_CTRL, &val8);
+	if (res)
+		return;
+
+	rtw_write8(Adapter, REG_BCN_CTRL, val8 | BIT(4));
 
 	/*  set net_type */
-	val8 = rtw_read8(Adapter, MSR) & 0x0c;
+	res = rtw_read8(Adapter, MSR, &val8);
+	if (res)
+		return;
+
+	val8 &= 0x0c;
 	val8 |= mode;
 	rtw_write8(Adapter, MSR, val8);
 
@@ -927,14 +998,22 @@ static void hw_var_set_opmode(struct adapter *Adapter, u8 *val)
 		rtw_write8(Adapter, REG_DUAL_TSF_RST, BIT(0));
 
 		/* BIT(3) - If set 0, hw will clr bcnq when tx becon ok/fail or port 0 */
-		rtw_write8(Adapter, REG_MBID_NUM, rtw_read8(Adapter, REG_MBID_NUM) | BIT(3) | BIT(4));
+		res = rtw_read8(Adapter, REG_MBID_NUM, &val8);
+		if (res)
+			return;
+
+		rtw_write8(Adapter, REG_MBID_NUM, val8 | BIT(3) | BIT(4));
 
 		/* enable BCN0 Function for if1 */
 		/* don't enable update TSF0 for if1 (due to TSF update when beacon/probe rsp are received) */
 		rtw_write8(Adapter, REG_BCN_CTRL, (DIS_TSF_UDT0_NORMAL_CHIP | EN_BCN_FUNCTION | BIT(1)));
 
 		/* dis BCN1 ATIM  WND if if2 is station */
-		rtw_write8(Adapter, REG_BCN_CTRL_1, rtw_read8(Adapter, REG_BCN_CTRL_1) | BIT(0));
+		res = rtw_read8(Adapter, REG_BCN_CTRL_1, &val8);
+		if (res)
+			return;
+
+		rtw_write8(Adapter, REG_BCN_CTRL_1, val8 | BIT(0));
 	}
 }
 
@@ -943,6 +1022,8 @@ void SetHwReg8188EU(struct adapter *Adapter, u8 variable, u8 *val)
 	struct hal_data_8188e *haldata = &Adapter->haldata;
 	struct dm_priv	*pdmpriv = &haldata->dmpriv;
 	struct odm_dm_struct *podmpriv = &haldata->odmpriv;
+	u8 reg;
+	int res;
 
 	switch (variable) {
 	case HW_VAR_SET_OPMODE:
@@ -970,7 +1051,11 @@ void SetHwReg8188EU(struct adapter *Adapter, u8 variable, u8 *val)
 			/*  Set RRSR rate table. */
 			rtw_write8(Adapter, REG_RRSR, BrateCfg & 0xff);
 			rtw_write8(Adapter, REG_RRSR + 1, (BrateCfg >> 8) & 0xff);
-			rtw_write8(Adapter, REG_RRSR + 2, rtw_read8(Adapter, REG_RRSR + 2) & 0xf0);
+			res = rtw_read8(Adapter, REG_RRSR + 2, &reg);
+			if (res)
+				return;
+
+			rtw_write8(Adapter, REG_RRSR + 2, reg & 0xf0);
 
 			/*  Set RTS initial rate */
 			while (BrateCfg > 0x1) {
@@ -994,13 +1079,21 @@ void SetHwReg8188EU(struct adapter *Adapter, u8 variable, u8 *val)
 				StopTxBeacon(Adapter);
 
 			/* disable related TSF function */
-			rtw_write8(Adapter, REG_BCN_CTRL, rtw_read8(Adapter, REG_BCN_CTRL) & (~BIT(3)));
+			res = rtw_read8(Adapter, REG_BCN_CTRL, &reg);
+			if (res)
+				return;
+
+			rtw_write8(Adapter, REG_BCN_CTRL, reg & (~BIT(3)));
 
 			rtw_write32(Adapter, REG_TSFTR, tsf);
 			rtw_write32(Adapter, REG_TSFTR + 4, tsf >> 32);
 
 			/* enable related TSF function */
-			rtw_write8(Adapter, REG_BCN_CTRL, rtw_read8(Adapter, REG_BCN_CTRL) | BIT(3));
+			res = rtw_read8(Adapter, REG_BCN_CTRL, &reg);
+			if (res)
+				return;
+
+			rtw_write8(Adapter, REG_BCN_CTRL, reg | BIT(3));
 
 			if (((pmlmeinfo->state & 0x03) == WIFI_FW_ADHOC_STATE) || ((pmlmeinfo->state & 0x03) == WIFI_FW_AP_STATE))
 				ResumeTxBeacon(Adapter);
@@ -1016,7 +1109,11 @@ void SetHwReg8188EU(struct adapter *Adapter, u8 variable, u8 *val)
 			rtw_write16(Adapter, REG_RXFLTMAP2, 0x00);
 
 			/* disable update TSF */
-			rtw_write8(Adapter, REG_BCN_CTRL, rtw_read8(Adapter, REG_BCN_CTRL) | BIT(4));
+			res = rtw_read8(Adapter, REG_BCN_CTRL, &reg);
+			if (res)
+				return;
+
+			rtw_write8(Adapter, REG_BCN_CTRL, reg | BIT(4));
 		} else { /* sitesurvey done */
 			struct mlme_ext_priv	*pmlmeext = &Adapter->mlmeextpriv;
 			struct mlme_ext_info	*pmlmeinfo = &pmlmeext->mlmext_info;
@@ -1027,11 +1124,19 @@ void SetHwReg8188EU(struct adapter *Adapter, u8 variable, u8 *val)
 				rtw_write16(Adapter, REG_RXFLTMAP2, 0xFFFF);
 
 				/* enable update TSF */
-				rtw_write8(Adapter, REG_BCN_CTRL, rtw_read8(Adapter, REG_BCN_CTRL) & (~BIT(4)));
+				res = rtw_read8(Adapter, REG_BCN_CTRL, &reg);
+				if (res)
+					return;
+
+				rtw_write8(Adapter, REG_BCN_CTRL, reg & (~BIT(4)));
 			} else if ((pmlmeinfo->state & 0x03) == WIFI_FW_AP_STATE) {
 				rtw_write16(Adapter, REG_RXFLTMAP2, 0xFFFF);
 				/* enable update TSF */
-				rtw_write8(Adapter, REG_BCN_CTRL, rtw_read8(Adapter, REG_BCN_CTRL) & (~BIT(4)));
+				res = rtw_read8(Adapter, REG_BCN_CTRL, &reg);
+				if (res)
+					return;
+
+				rtw_write8(Adapter, REG_BCN_CTRL, reg & (~BIT(4)));
 			}
 			rtw_write32(Adapter, REG_RCR, rtw_read32(Adapter, REG_RCR) | RCR_CBSSID_BCN);
 		}
@@ -1166,6 +1271,8 @@ void SetBeaconRelatedRegisters8188EUsb(struct adapter *adapt)
 	struct mlme_ext_priv	*pmlmeext = &adapt->mlmeextpriv;
 	struct mlme_ext_info	*pmlmeinfo = &pmlmeext->mlmext_info;
 	u32 bcn_ctrl_reg			= REG_BCN_CTRL;
+	int res;
+	u8 reg;
 	/* reset TSF, enable update TSF, correcting TSF On Beacon */
 
 	/* BCN interval */
@@ -1191,7 +1298,11 @@ void SetBeaconRelatedRegisters8188EUsb(struct adapter *adapt)
 
 	ResumeTxBeacon(adapt);
 
-	rtw_write8(adapt, bcn_ctrl_reg, rtw_read8(adapt, bcn_ctrl_reg) | BIT(1));
+	res = rtw_read8(adapt, bcn_ctrl_reg, &reg);
+	if (res)
+		return;
+
+	rtw_write8(adapt, bcn_ctrl_reg, reg | BIT(1));
 }
 
 void rtl8188eu_init_default_value(struct adapter *adapt)

drivers/staging/r8188eu/hal/usb_ops_linux.c

@@ -94,16 +94,13 @@ static int usb_write(struct intf_hdl *intf, u16 value, void *data, u8 size)
 	return status;
 }
 
-u8 rtw_read8(struct adapter *adapter, u32 addr)
+int __must_check rtw_read8(struct adapter *adapter, u32 addr, u8 *data)
 {
 	struct io_priv *io_priv = &adapter->iopriv;
 	struct intf_hdl *intf = &io_priv->intf;
 	u16 value = addr & 0xffff;
-	u8 data;
 
-	usb_read(intf, value, &data, 1);
-
-	return data;
+	return usb_read(intf, value, data, 1);
 }
 
 u16 rtw_read16(struct adapter *adapter, u32 addr)

drivers/staging/r8188eu/include/rtw_io.h

@@ -220,7 +220,7 @@ void unregister_intf_hdl(struct intf_hdl *pintfhdl);
 void _rtw_attrib_read(struct adapter *adapter, u32 addr, u32 cnt, u8 *pmem);
 void _rtw_attrib_write(struct adapter *adapter, u32 addr, u32 cnt, u8 *pmem);
 
-u8 rtw_read8(struct adapter *adapter, u32 addr);
+int __must_check rtw_read8(struct adapter *adapter, u32 addr, u8 *data);
 u16 rtw_read16(struct adapter *adapter, u32 addr);
 u32 rtw_read32(struct adapter *adapter, u32 addr);
 void _rtw_read_mem(struct adapter *adapter, u32 addr, u32 cnt, u8 *pmem);

drivers/staging/r8188eu/os_dep/ioctl_linux.c

@@ -3178,6 +3178,7 @@ static void rtw_set_dynamic_functions(struct adapter *adapter, u8 dm_func)
 {
 	struct hal_data_8188e *haldata = &adapter->haldata;
 	struct odm_dm_struct *odmpriv = &haldata->odmpriv;
+	int res;
 
 	switch (dm_func) {
 	case 0:
@@ -3193,7 +3194,9 @@ static void rtw_set_dynamic_functions(struct adapter *adapter, u8 dm_func)
 		if (!(odmpriv->SupportAbility & DYNAMIC_BB_DIG)) {
 			struct rtw_dig *digtable = &odmpriv->DM_DigTable;
 
-			digtable->CurIGValue = rtw_read8(adapter, 0xc50);
+			res = rtw_read8(adapter, 0xc50, &digtable->CurIGValue);
+			(void)res;
+			/* FIXME: return an error to caller */
 		}
 		odmpriv->SupportAbility = DYNAMIC_ALL_FUNC_ENABLE;
 		break;
@@ -3329,8 +3332,9 @@ static int rtw_dbg_port(struct net_device *dev,
 			u16 reg = arg;
 			u16 start_value = 0;
 			u32 write_num = extra_arg;
-			int i;
+			int i, res;
 			struct xmit_frame	*xmit_frame;
+			u8 val8;
 
 			xmit_frame = rtw_IOL_accquire_xmit_frame(padapter);
 			if (!xmit_frame) {
@@ -3343,7 +3347,8 @@ static int rtw_dbg_port(struct net_device *dev,
 			if (rtl8188e_IOL_exec_cmds_sync(padapter, xmit_frame, 5000, 0) != _SUCCESS)
 				ret = -EPERM;
 
-			rtw_read8(padapter, reg);
+			/* FIXME: is this read necessary? */
+			res = rtw_read8(padapter, reg, &val8);
 		}
 			break;