Subject: [RFC PATCH 17/17] net: Drop uses of pci_read_config_*() return value

From: "Saheed O. Bolarinwa" <[email-masked]>
Date: Sat, 1 Aug 2020 13:24:46 +0200

The return value of pci_read_config_*() may not indicate a device error.
However, the value read by these functions is more likely to indicate
this kind of error. This presents two overlapping ways of reporting
errors and complicates error checking.

It is possible to move to one single way of checking for error if the
dependency on the return value of these functions is removed, then it
can later be made to return void.

Remove all uses of the return value of pci_read_config_*().
Check the actual value read for ~0. In this case, ~0 is an invalid
value thus it indicates some kind of error.

Suggested-by: Bjorn Helgaas <[email-masked]>
Signed-off-by: Saheed O. Bolarinwa <[email-masked]>
---
 drivers/net/can/peak_canfd/peak_pciefd_main.c     |  6 ++++--
 drivers/net/can/sja1000/peak_pci.c                |  6 ++++--
 drivers/net/ethernet/agere/et131x.c               | 11 +++++++----
 .../net/ethernet/broadcom/bnx2x/bnx2x_ethtool.c   |  5 +++--
 .../ethernet/cavium/liquidio/cn23xx_pf_device.c   |  4 ++--
 drivers/net/ethernet/marvell/sky2.c               |  5 +++--
 drivers/net/ethernet/mellanox/mlx4/catas.c        |  7 +------
 drivers/net/ethernet/mellanox/mlx4/reset.c        | 10 ++++++----
 drivers/net/ethernet/myricom/myri10ge/myri10ge.c  |  4 ++--
 drivers/net/wan/farsync.c                         |  5 +++--
 .../wireless/broadcom/brcm80211/brcmfmac/pcie.c   |  4 ++--
 drivers/net/wireless/intel/iwlwifi/pcie/trans.c   | 15 ++++++++++-----
 12 files changed, 47 insertions(+), 35 deletions(-)

diff --git a/drivers/net/can/peak_canfd/peak_pciefd_main.c b/drivers/net/can/peak_canfd/peak_pciefd_main.c
index 6ad83a881039..484a214fc1f1 100644
--- a/drivers/net/can/peak_canfd/peak_pciefd_main.c
+++ b/drivers/net/can/peak_canfd/peak_pciefd_main.c
@@ -730,9 +730,11 @@ static int peak_pciefd_probe(struct pci_dev *pdev,
 		goto err_disable_pci;
 
 	/* the number of channels depends on sub-system id */
-	err = pci_read_config_word(pdev, PCI_SUBSYSTEM_ID, &sub_sys_id);
-	if (err)
+	pci_read_config_word(pdev, PCI_SUBSYSTEM_ID, &sub_sys_id);
+	if (sub_sys_id == (u16)~0) {
+		err = -ENODEV;
 		goto err_release_regions;
+	}
 
 	dev_dbg(&pdev->dev, "probing device %04x:%04x:%04x\n",
 		pdev->vendor, pdev->device, sub_sys_id);
diff --git a/drivers/net/can/sja1000/peak_pci.c b/drivers/net/can/sja1000/peak_pci.c
index 8c0244f51059..d25a99ad08da 100644
--- a/drivers/net/can/sja1000/peak_pci.c
+++ b/drivers/net/can/sja1000/peak_pci.c
@@ -560,9 +560,11 @@ static int peak_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	if (err)
 		goto failure_disable_pci;
 
-	err = pci_read_config_word(pdev, 0x2e, &sub_sys_id);
-	if (err)
+	pci_read_config_word(pdev, 0x2e, &sub_sys_id);
+	if (sub_sys_id == (u16)~0) {
+		err = -ENODEV;
 		goto failure_release_regions;
+	}
 
 	dev_dbg(&pdev->dev, "probing device %04x:%04x:%04x\n",
 		pdev->vendor, pdev->device, sub_sys_id);
diff --git a/drivers/net/ethernet/agere/et131x.c b/drivers/net/ethernet/agere/et131x.c
index 865892c1f23f..6b0e5f193e73 100644
--- a/drivers/net/ethernet/agere/et131x.c
+++ b/drivers/net/ethernet/agere/et131x.c
@@ -505,7 +505,8 @@ static int eeprom_wait_ready(struct pci_dev *pdev, u32 *status)
 	 *    to 1 prior to starting a single byte read/write
 	 */
 	for (i = 0; i < MAX_NUM_REGISTER_POLLS; i++) {
-		if (pci_read_config_dword(pdev, LBCIF_DWORD1_GROUP, &reg))
+		pci_read_config_dword(pdev, LBCIF_DWORD1_GROUP, &reg);
+		if (reg == (u32)~0)
 			return -EIO;
 
 		/* I2C idle and Phy Queue Avail both true */
@@ -679,7 +680,8 @@ static int et131x_init_eeprom(struct et131x_adapter *adapter)
 	 * function, because I thought there could be some time conditions
 	 * but it didn't work. Call the whole function twice also work.
 	 */
-	if (pci_read_config_byte(pdev, ET1310_PCI_EEPROM_STATUS, &eestatus)) {
+	pci_read_config_byte(pdev, ET1310_PCI_EEPROM_STATUS, &eestatus);
+	if (eestatus == (u8)~0) {
 		dev_err(&pdev->dev,
 			"Could not read PCI config space for EEPROM Status\n");
 		return -EIO;
@@ -3059,8 +3061,9 @@ static int et131x_pci_init(struct et131x_adapter *adapter,
 	}
 
 	for (i = 0; i < ETH_ALEN; i++) {
-		if (pci_read_config_byte(pdev, ET1310_PCI_MAC_ADDRESS + i,
-					 adapter->rom_addr + i)) {
+		pci_read_config_byte(pdev, ET1310_PCI_MAC_ADDRESS + i,
+					 adapter->rom_addr + i);
+		if (*(adapter->rom_addr + i) == (u8)~0) {
 			dev_err(&pdev->dev, "Could not read PCI config space for MAC address\n");
 			goto err_out;
 		}
diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_ethtool.c b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_ethtool.c
index 7cea33803f7f..5962a1d2dffc 100644
--- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_ethtool.c
+++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_ethtool.c
@@ -1463,14 +1463,15 @@ static int bnx2x_nvram_read32(struct bnx2x *bp, u32 offset, u32 *buf,
 
 static bool bnx2x_is_nvm_accessible(struct bnx2x *bp)
 {
-	int rc = 1;
+	bool rc = true;
 	u16 pm = 0;
 	struct net_device *dev = pci_get_drvdata(bp->pdev);
 
 	if (bp->pdev->pm_cap)
-		rc = pci_read_config_word(bp->pdev,
+		pci_read_config_word(bp->pdev,
 					  bp->pdev->pm_cap + PCI_PM_CTRL, &pm);
 
+	rc = (pm == (u16)~0);
 	if ((rc && !netif_running(dev)) ||
 	    (!rc && ((pm & PCI_PM_CTRL_STATE_MASK) != (__force u16)PCI_D0)))
 		return false;
diff --git a/drivers/net/ethernet/cavium/liquidio/cn23xx_pf_device.c b/drivers/net/ethernet/cavium/liquidio/cn23xx_pf_device.c
index 43d11c38b38a..cf52d6cc2a46 100644
--- a/drivers/net/ethernet/cavium/liquidio/cn23xx_pf_device.c
+++ b/drivers/net/ethernet/cavium/liquidio/cn23xx_pf_device.c
@@ -1162,8 +1162,8 @@ static int cn23xx_get_pf_num(struct octeon_device *oct)
 	ret = 0;
 
 	/** Read Function Dependency Link reg to get the function number */
-	if (pci_read_config_dword(oct->pci_dev, CN23XX_PCIE_SRIOV_FDL,
-				  &fdl_bit) == 0) {
+	pci_read_config_dword(oct->pci_dev, CN23XX_PCIE_SRIOV_FDL, &fdl_bit);
+	if (fdl_bit != (u32)~0) {
 		oct->pf_num = ((fdl_bit >> CN23XX_PCIE_SRIOV_FDL_BIT_POS) &
 			       CN23XX_PCIE_SRIOV_FDL_MASK);
 	} else {
diff --git a/drivers/net/ethernet/marvell/sky2.c b/drivers/net/ethernet/marvell/sky2.c
index fe54764caea9..1042bfd0ff70 100644
--- a/drivers/net/ethernet/marvell/sky2.c
+++ b/drivers/net/ethernet/marvell/sky2.c
@@ -4964,8 +4964,9 @@ static int sky2_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	 *       other PCI access through shared memory for speed and to
 	 *	 avoid MMCONFIG problems.
 	 */
-	err = pci_read_config_dword(pdev, PCI_DEV_REG2, &reg);
-	if (err) {
+	pci_read_config_dword(pdev, PCI_DEV_REG2, &reg);
+	if (reg == (u32)~0) {
+		err = -ENODEV;
 		dev_err(&pdev->dev, "PCI read config failed\n");
 		goto err_out_disable;
 	}
diff --git a/drivers/net/ethernet/mellanox/mlx4/catas.c b/drivers/net/ethernet/mellanox/mlx4/catas.c
index 5b11557f1ae4..1e774a181133 100644
--- a/drivers/net/ethernet/mellanox/mlx4/catas.c
+++ b/drivers/net/ethernet/mellanox/mlx4/catas.c
@@ -52,12 +52,7 @@ static int read_vendor_id(struct mlx4_dev *dev)
 	u16 vendor_id = 0;
 	int ret;
 
-	ret = pci_read_config_word(dev->persist->pdev, 0, &vendor_id);
-	if (ret) {
-		mlx4_err(dev, "Failed to read vendor ID, ret=%d\n", ret);
-		return ret;
-	}
-
+	pci_read_config_word(dev->persist->pdev, 0, &vendor_id);
 	if (vendor_id == 0xffff) {
 		mlx4_err(dev, "PCI can't be accessed to read vendor id\n");
 		return -EINVAL;
diff --git a/drivers/net/ethernet/mellanox/mlx4/reset.c b/drivers/net/ethernet/mellanox/mlx4/reset.c
index 0076d88587ca..f0b9af99aa26 100644
--- a/drivers/net/ethernet/mellanox/mlx4/reset.c
+++ b/drivers/net/ethernet/mellanox/mlx4/reset.c
@@ -81,8 +81,9 @@ int mlx4_reset(struct mlx4_dev *dev)
 	for (i = 0; i < 64; ++i) {
 		if (i == 22 || i == 23)
 			continue;
-		if (pci_read_config_dword(dev->persist->pdev, i * 4,
-					  hca_header + i)) {
+		pci_read_config_dword(dev->persist->pdev, i * 4,
+							hca_header + i);
+		if (*(hca_header + i) == (u32)~0) {
 			err = -ENODEV;
 			mlx4_err(dev, "Couldn't save HCA PCI header, aborting\n");
 			goto out;
@@ -124,8 +125,9 @@ int mlx4_reset(struct mlx4_dev *dev)
 
 	end = jiffies + MLX4_RESET_TIMEOUT_JIFFIES;
 	do {
-		if (!pci_read_config_word(dev->persist->pdev, PCI_VENDOR_ID,
-					  &vendor) && vendor != 0xffff)
+		pci_read_config_word(dev->persist->pdev, PCI_VENDOR_ID,
+					&vendor);
+		if (vendor != 0xffff)
 			break;
 
 		msleep(1);
diff --git a/drivers/net/ethernet/myricom/myri10ge/myri10ge.c b/drivers/net/ethernet/myricom/myri10ge/myri10ge.c
index e1e1f4e3639e..b1b055f8ac47 100644
--- a/drivers/net/ethernet/myricom/myri10ge/myri10ge.c
+++ b/drivers/net/ethernet/myricom/myri10ge/myri10ge.c
@@ -3090,8 +3090,8 @@ static void myri10ge_enable_ecrc(struct myri10ge_priv *mgp)
 	if (!cap)
 		return;
 
-	ret = pci_read_config_dword(bridge, cap + PCI_ERR_CAP, &err_cap);
-	if (ret) {
+	pci_read_config_dword(bridge, cap + PCI_ERR_CAP, &err_cap);
+	if (err_cap == (u32)~0) {
 		dev_err(dev, "failed reading ext-conf-space of %s\n",
 			pci_name(bridge));
 		dev_err(dev, "\t pci=nommconf in use? "
diff --git a/drivers/net/wan/farsync.c b/drivers/net/wan/farsync.c
index 7916efce7188..8981334d9f82 100644
--- a/drivers/net/wan/farsync.c
+++ b/drivers/net/wan/farsync.c
@@ -678,8 +678,9 @@ fst_cpureset(struct fst_card_info *card)
 	unsigned int regval;
 
 	if (card->family == FST_FAMILY_TXU) {
-		if (pci_read_config_byte
-		    (card->device, PCI_INTERRUPT_LINE, &interrupt_line_register)) {
+		pci_read_config_byte
+		    (card->device, PCI_INTERRUPT_LINE, &interrupt_line_register);
+		if (interrupt_line_register == (u8)~0) {
 			dbg(DBG_ASS,
 			    "Error in reading interrupt line register\n");
 		}
diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
index 39381cbde89e..f501b4759630 100644
--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.c
@@ -544,8 +544,8 @@ brcmf_pcie_select_core(struct brcmf_pciedev_info *devinfo, u16 coreid)
 	if (core) {
 		bar0_win = core->base;
 		pci_write_config_dword(pdev, BRCMF_PCIE_BAR0_WINDOW, bar0_win);
-		if (pci_read_config_dword(pdev, BRCMF_PCIE_BAR0_WINDOW,
-					  &bar0_win) == 0) {
+		pci_read_config_dword(pdev, BRCMF_PCIE_BAR0_WINDOW, &bar0_win);
+		if (bar0_win != (u32)~0) {
 			if (bar0_win != core->base) {
 				bar0_win = core->base;
 				pci_write_config_dword(pdev,
diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
index e5160d620868..caafad424aa7 100644
--- a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
+++ b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
@@ -122,7 +122,8 @@ void iwl_trans_pcie_dump_regs(struct iwl_trans *trans)
 	sprintf(prefix, "iwlwifi %s: ", pci_name(pdev));
 	IWL_ERR(trans, "iwlwifi device config registers:\n");
 	for (i = 0, ptr = buf; i < PCI_DUMP_SIZE; i += 4, ptr++)
-		if (pci_read_config_dword(pdev, i, ptr))
+		pci_read_config_dword(pdev, i, ptr);
+		if (*ptr == (u32)~0)
 			goto err_read;
 	print_hex_dump(KERN_ERR, prefix, DUMP_PREFIX_OFFSET, 32, 4, buf, i, 0);
 
@@ -135,7 +136,8 @@ void iwl_trans_pcie_dump_regs(struct iwl_trans *trans)
 	if (pos) {
 		IWL_ERR(trans, "iwlwifi device AER capability structure:\n");
 		for (i = 0, ptr = buf; i < PCI_ERR_ROOT_COMMAND; i += 4, ptr++)
-			if (pci_read_config_dword(pdev, pos + i, ptr))
+			pci_read_config_dword(pdev, pos + i, ptr);
+			if (*ptr == (u32)~0)
 				goto err_read;
 		print_hex_dump(KERN_ERR, prefix, DUMP_PREFIX_OFFSET,
 			       32, 4, buf, i, 0);
@@ -151,7 +153,8 @@ void iwl_trans_pcie_dump_regs(struct iwl_trans *trans)
 	IWL_ERR(trans, "iwlwifi parent port (%s) config registers:\n",
 		pci_name(pdev));
 	for (i = 0, ptr = buf; i < PCI_PARENT_DUMP_SIZE; i += 4, ptr++)
-		if (pci_read_config_dword(pdev, i, ptr))
+		pci_read_config_dword(pdev, i, ptr);
+		if (*ptr == (u32)~0)
 			goto err_read;
 	print_hex_dump(KERN_ERR, prefix, DUMP_PREFIX_OFFSET, 32, 4, buf, i, 0);
 
@@ -165,7 +168,8 @@ void iwl_trans_pcie_dump_regs(struct iwl_trans *trans)
 			pci_name(pdev));
 		sprintf(prefix, "iwlwifi %s: ", pci_name(pdev));
 		for (i = 0, ptr = buf; i <= PCI_ERR_ROOT_ERR_SRC; i += 4, ptr++)
-			if (pci_read_config_dword(pdev, pos + i, ptr))
+			pci_read_config_dword(pdev, pos + i, ptr);
+			if (*ptr == (u32)~0)
 				goto err_read;
 		print_hex_dump(KERN_ERR, prefix, DUMP_PREFIX_OFFSET, 32,
 			       4, buf, i, 0);
@@ -2191,8 +2195,9 @@ static int iwl_trans_pcie_write_mem(struct iwl_trans *trans, u32 addr,
 static int iwl_trans_pcie_read_config32(struct iwl_trans *trans, u32 ofs,
 					u32 *val)
 {
-	return pci_read_config_dword(IWL_TRANS_GET_PCIE_TRANS(trans)->pci_dev,
+	pci_read_config_dword(IWL_TRANS_GET_PCIE_TRANS(trans)->pci_dev,
 				     ofs, val);
+	return (*val == (u32)~0) ? -ENODEV : 0;
 }
 
 static void iwl_trans_pcie_freeze_txq_timer(struct iwl_trans *trans,
-- 
2.18.4