gpio: Prevent an integer overflow in the pca953x driver

Interrupts were missed if an 8-bit integer overflow occurred. This was
observed when bank0,pin7 and bank1,pin7 changed simultaniously.

As the 8-bit totals were only checked against zero, replace them with
booleans. Name the booleans so that their purpose is clear.

Signed-off-by: Joshua Scott <joshua.scott@alliedtelesis.co.nz>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
index eed4203..d233eb3 100644 (file)
--- a/drivers/gpio/gpio-pca953x.c
+++ b/drivers/gpio/gpio-pca953x.c
@@ -443,12 +443,13 @@ static struct irq_chip pca953x_irq_chip = {
        .irq_set_type           = pca953x_irq_set_type,
 };
 
-static u8 pca953x_irq_pending(struct pca953x_chip *chip, u8 *pending)
+static bool pca953x_irq_pending(struct pca953x_chip *chip, u8 *pending)
 {
        u8 cur_stat[MAX_BANK];
        u8 old_stat[MAX_BANK];
-       u8 pendings = 0;
-       u8 trigger[MAX_BANK], triggers = 0;
+       bool pending_seen = false;
+       bool trigger_seen = false;
+       u8 trigger[MAX_BANK];
        int ret, i, offset = 0;
 
        switch (chip->chip_type) {
@@ -461,7 +462,7 @@ static u8 pca953x_irq_pending(struct pca953x_chip *chip, u8 *pending)
        }
        ret = pca953x_read_regs(chip, offset, cur_stat);
        if (ret)
-               return 0;
+               return false;
 
        /* Remove output pins from the equation */
        for (i = 0; i < NBANK(chip); i++)
@@ -471,11 +472,12 @@ static u8 pca953x_irq_pending(struct pca953x_chip *chip, u8 *pending)
 
        for (i = 0; i < NBANK(chip); i++) {
                trigger[i] = (cur_stat[i] ^ old_stat[i]) & chip->irq_mask[i];
-               triggers += trigger[i];
+               if (trigger[i])
+                       trigger_seen = true;
        }
 
-       if (!triggers)
-               return 0;
+       if (!trigger_seen)
+               return false;
 
        memcpy(chip->irq_stat, cur_stat, NBANK(chip));
 
@@ -483,10 +485,11 @@ static u8 pca953x_irq_pending(struct pca953x_chip *chip, u8 *pending)
                pending[i] = (old_stat[i] & chip->irq_trig_fall[i]) |
                        (cur_stat[i] & chip->irq_trig_raise[i]);
                pending[i] &= trigger[i];
-               pendings += pending[i];
+               if (pending[i])
+                       pending_seen = true;
        }
 
-       return pendings;
+       return pending_seen;
 }
 
 static irqreturn_t pca953x_irq_handler(int irq, void *devid)