linux-kernel - [RFC PATCH 08/17] gpio: Drop uses of pci_read_config

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Date:   Sat,  1 Aug 2020 13:24:37 +0200
From:   "Saheed O. Bolarinwa" <refactormyself@...il.com>
To:     helgaas@...nel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Linus Walleij <linus.walleij@...aro.org>
Cc:     "Saheed O. Bolarinwa" <refactormyself@...il.com>,
        bjorn@...gaas.com, skhan@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-gpio@...r.kernel.org
Subject: [RFC PATCH 08/17] gpio: Drop uses of pci_read_config_*() return value

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 <bjorn@...gaas.com>
Signed-off-by: Saheed O. Bolarinwa <refactormyself@...il.com>
---
 drivers/gpio/gpio-amd8111.c |  7 +++++--
 drivers/gpio/gpio-rdc321x.c | 21 ++++++++++++---------
 2 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/drivers/gpio/gpio-amd8111.c b/drivers/gpio/gpio-amd8111.c
index fdcebe59510d..7b9882380cbc 100644
--- a/drivers/gpio/gpio-amd8111.c
+++ b/drivers/gpio/gpio-amd8111.c
@@ -198,9 +198,12 @@ static int __init amd_gpio_init(void)
 	goto out;
 
 found:
-	err = pci_read_config_dword(pdev, 0x58, &gp.pmbase);
-	if (err)
+	pci_read_config_dword(pdev, 0x58, &gp.pmbase);
+	if (gp.pmbase == (u32)~0) {
+		err = -ENODEV;
 		goto out;
+	}
+
 	err = -EIO;
 	gp.pmbase &= 0x0000FF00;
 	if (gp.pmbase == 0)
diff --git a/drivers/gpio/gpio-rdc321x.c b/drivers/gpio/gpio-rdc321x.c
index 01ed2517e9fd..03f1ff07b844 100644
--- a/drivers/gpio/gpio-rdc321x.c
+++ b/drivers/gpio/gpio-rdc321x.c
@@ -85,10 +85,13 @@ static int rdc_gpio_config(struct gpio_chip *chip,
 	gpch = gpiochip_get_data(chip);
 
 	spin_lock(&gpch->lock);
-	err = pci_read_config_dword(gpch->sb_pdev, gpio < 32 ?
-			gpch->reg1_ctrl_base : gpch->reg2_ctrl_base, &reg);
-	if (err)
+	pci_read_config_dword(gpch->sb_pdev,
+				(gpio < 32) ? gpch->reg1_ctrl_base
+					: gpch->reg2_ctrl_base, &reg);
+	if (reg == (u32)~0) {
+		err = -ENODEV;
 		goto unlock;
+	}
 
 	reg |= 1 << (gpio & 0x1f);
 
@@ -166,17 +169,17 @@ static int rdc321x_gpio_probe(struct platform_device *pdev)
 	/* This might not be, what others (BIOS, bootloader, etc.)
 	   wrote to these registers before, but it's a good guess. Still
 	   better than just using 0xffffffff. */
-	err = pci_read_config_dword(rdc321x_gpio_dev->sb_pdev,
+	pci_read_config_dword(rdc321x_gpio_dev->sb_pdev,
 					rdc321x_gpio_dev->reg1_data_base,
 					&rdc321x_gpio_dev->data_reg[0]);
-	if (err)
-		return err;
+	if (rdc321x_gpio_dev->data_reg[0] == (u32)~0)
+		return -ENODEV;
 
-	err = pci_read_config_dword(rdc321x_gpio_dev->sb_pdev,
+	pci_read_config_dword(rdc321x_gpio_dev->sb_pdev,
 					rdc321x_gpio_dev->reg2_data_base,
 					&rdc321x_gpio_dev->data_reg[1]);
-	if (err)
-		return err;
+	if (rdc321x_gpio_dev->data_reg[1] == (u32)~0)
+		return -ENODEV;
 
 	dev_info(&pdev->dev, "registering %d GPIOs\n",
 					rdc321x_gpio_dev->chip.ngpio);
-- 
2.18.4