On 03/16/2017 07:57 PM, David Rivshin wrote:
> From: David Rivshin <DRivshin@xxxxxxxxxxx>
>
> omap_gpio_debounce() does not validate that the requested debounce
> is within a range it can handle. Instead it lets the register value
> wrap silently, and always returns success.
>
> This can lead to all sorts of unexpected behavior, such as gpio_keys
> asking for a too-long debounce, but getting a very short debounce in
> practice.
>
> Fix this by returning -EINVAL if the requested value does not fit into
> the register field. If there is no debounce clock available at all,
> return -ENOTSUPP.
In general this patch looks good, but there is one thing I'm worry about..
>
> Fixes: e85ec6c3047b ("gpio: omap: fix omap2_set_gpio_debounce")
> Cc: <stable@xxxxxxxxxxxxxxx> # 4.3+
> Signed-off-by: David Rivshin <drivshin@xxxxxxxxxxx>
> ---
> drivers/gpio/gpio-omap.c | 16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpio/gpio-omap.c b/drivers/gpio/gpio-omap.c
> index efc85a2..33ec02d 100644
> --- a/drivers/gpio/gpio-omap.c
> +++ b/drivers/gpio/gpio-omap.c
> @@ -208,8 +208,10 @@ static inline void omap_gpio_dbck_disable(struct gpio_bank *bank)
> * OMAP's debounce time is in 31us steps
> * <debounce time> = (GPIO_DEBOUNCINGTIME[7:0].DEBOUNCETIME + 1) x 31
> * so we need to convert and round up to the closest unit.
> + *
> + * Return: 0 on success, negative error otherwise.
> */
> -static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> +static int omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> unsigned debounce)
> {
> void __iomem *reg;
> @@ -218,11 +220,12 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> bool enable = !!debounce;
>
> if (!bank->dbck_flag)
> - return;
> + return -ENOTSUPP;
>
> if (enable) {
> debounce = DIV_ROUND_UP(debounce, 31) - 1;
> - debounce &= OMAP4_GPIO_DEBOUNCINGTIME_MASK;
> + if ((debounce & OMAP4_GPIO_DEBOUNCINGTIME_MASK) != debounce)
> + return -EINVAL;
This might cause boot issues as current drivers may expect this op to succeed even if
configured value is wrong - just think, may be we can do warn here and use max value as
fallback?
> }
>
> l = BIT(offset);
> @@ -255,6 +258,8 @@ static void omap2_set_gpio_debounce(struct gpio_bank *bank, unsigned offset,
> bank->context.debounce = debounce;
> bank->context.debounce_en = val;
> }
> +
> + return 0;
> }
>
> /**
> @@ -964,14 +969,15 @@ static int omap_gpio_debounce(struct gpio_chip *chip, unsigned offset,
> {
> struct gpio_bank *bank;
> unsigned long flags;
> + int ret;
>
> bank = gpiochip_get_data(chip);
>
> raw_spin_lock_irqsave(&bank->lock, flags);
> - omap2_set_gpio_debounce(bank, offset, debounce);
> + ret = omap2_set_gpio_debounce(bank, offset, debounce);
> raw_spin_unlock_irqrestore(&bank->lock, flags);
>
> - return 0;
> + return ret;
> }
>
> static int omap_gpio_set_config(struct gpio_chip *chip, unsigned offset,
>
--
regards,
-grygorii