linux-kernel - [PATCH] GPIO, Fix bug where the wrong GPIO register is written to

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Message-Id: <20200125221410.8022-1-pthomas8589@gmail.com>
Date:   Sat, 25 Jan 2020 17:14:10 -0500
From:   Paul Thomas <pthomas8589@...il.com>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Michal Simek <michal.simek@...inx.com>,
        linux-gpio@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     Paul Thomas <pthomas8589@...il.com>
Subject: [PATCH] GPIO, Fix bug where the wrong GPIO register is written to

Care is taken with "index", however with the current version
the actual xgpio_writereg is using index for data but
xgpio_regoffset(chip, i) for the offset. And since i is already
incremented it is incorrect. This patch fixes it so that index
is used for the offset too.

Signed-off-by: Paul Thomas <pthomas8589@...il.com>
---
 There are many different ways to correct this, I'd just like it to get
 fixed. I've tested this with a 5.2 kernel, but this patch is against
 5.5rc7.

 drivers/gpio/gpio-xilinx.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpio-xilinx.c b/drivers/gpio/gpio-xilinx.c
index a9748b5198e6..67f9f82e0db0 100644
--- a/drivers/gpio/gpio-xilinx.c
+++ b/drivers/gpio/gpio-xilinx.c
@@ -147,9 +147,10 @@ static void xgpio_set_multiple(struct gpio_chip *gc, unsigned long *mask,
 	for (i = 0; i < gc->ngpio; i++) {
 		if (*mask == 0)
 			break;
+		/* Once finished with an index write it out to the register */
 		if (index !=  xgpio_index(chip, i)) {
 			xgpio_writereg(chip->regs + XGPIO_DATA_OFFSET +
-				       xgpio_regoffset(chip, i),
+				       index * XGPIO_CHANNEL_OFFSET,
 				       chip->gpio_state[index]);
 			spin_unlock_irqrestore(&chip->gpio_lock[index], flags);
 			index =  xgpio_index(chip, i);
@@ -165,7 +166,7 @@ static void xgpio_set_multiple(struct gpio_chip *gc, unsigned long *mask,
 	}
 
 	xgpio_writereg(chip->regs + XGPIO_DATA_OFFSET +
-		       xgpio_regoffset(chip, i), chip->gpio_state[index]);
+		       index * XGPIO_CHANNEL_OFFSET, chip->gpio_state[index]);
 
 	spin_unlock_irqrestore(&chip->gpio_lock[index], flags);
 }
-- 
2.17.1