linux-kernel - Re: [PATCH] pinctrl: st: Fix Sparse error

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Date:	Mon, 29 Sep 2014 20:35:42 +0530
From:	Pramod Gurav <pramod.gurav.etc@...il.com>
To:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:	Pramod Gurav <pramod.gurav@...rtplayin.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Maxime Coquelin <maxime.coquelin@...com>,
	Patrice Chotard <patrice.chotard@...com>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH] pinctrl: st: Fix Sparse error

Hi Srini,

Thanks for review.

On Mon, Sep 29, 2014 at 8:16 PM, Srinivas Kandagatla
<srinivas.kandagatla@...aro.org> wrote:
> On 29/09/14 14:48, Pramod Gurav wrote:
>>
>> This change fixes below sparse error,
>> drivers/pinctrl/pinctrl-st.c:1515:31: error: incompatible types for
>> operation (>)
>> drivers/pinctrl/pinctrl-st.c:1515:31:    left side has type void [noderef]
>> <asn:2>*irqmux_base
>> drivers/pinctrl/pinctrl-st.c:1515:31:    right side has type int
>>
>> The fix is done by removing a check on info->irqmux_base as
>> info->irqmux_base has already been checked  for error when allocating it.
>> Hence there is no need to redo the check.
>>
>> Cc: Maxime Coquelin <maxime.coquelin@...com>
>> Cc: Patrice Chotard <patrice.chotard@...com>
>> CC: Linus Walleij <linus.walleij@...aro.org>
>> Cc: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
>> Signed-off-by: Pramod Gurav <pramod.gurav@...rtplayin.com>
>> ---
>>   drivers/pinctrl/pinctrl-st.c |    2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/pinctrl/pinctrl-st.c b/drivers/pinctrl/pinctrl-st.c
>> index 5475374..ddeaeda 100644
>> --- a/drivers/pinctrl/pinctrl-st.c
>> +++ b/drivers/pinctrl/pinctrl-st.c
>> @@ -1512,7 +1512,7 @@ static int st_gpiolib_register_bank(struct
>> st_pinctrl *info,
>>                                              gpio_irq,
>> st_gpio_irq_handler);
>>         }
>>
>> -       if (info->irqmux_base > 0 || gpio_irq > 0) {
>> +       if (gpio_irq > 0) {
>>                 err = gpiochip_irqchip_add(&bank->gpio_chip,
>> &st_gpio_irqchip,
>>                                            0, handle_simple_irq,
>>                                            IRQ_TYPE_LEVEL_LOW);
>
>
> This is not the correct fix. Please see why irqmux_base and gpio_irq are
> used in the driver.
> You are breaking the logic here...
>
> please read the below comment from the code.
>
>         /**
>          * GPIO bank can have one of the two possible types of
>          * interrupt-wirings.
>          *
>          * First type is via irqmux, single interrupt is used by multiple
>          * gpio banks. This reduces number of overall interrupts numbers
>          * required. All these banks belong to a single pincontroller.
>          *                _________
>          *               |         |----> [gpio-bank (n)    ]
>          *               |         |----> [gpio-bank (n + 1)]
>          *      [irqN]-- | irq-mux |----> [gpio-bank (n + 2)]
>          *               |         |----> [gpio-bank (...  )]
>          *               |_________|----> [gpio-bank (n + 7)]
>          *
>          * Second type has a dedicated interrupt per each gpio bank.
>          *
>          *      [irqN]----> [gpio-bank (n)]
>          */
>
>
> so irqmux_base is first type and gpio_irq is second type.
> if you remove check for irqmux_base here you would end up NOT adding irqchip
> the gpiochip in first type so you break the existing logic here.
>
>
Thanks for this nice explanation.

> I think the correct fix is:
>
> diff --git a/drivers/pinctrl/pinctrl-st.c b/drivers/pinctrl/pinctrl-st.c
> index 5475374..4060c30 100644
> --- a/drivers/pinctrl/pinctrl-st.c
> +++ b/drivers/pinctrl/pinctrl-st.c
> @@ -1512,7 +1512,7 @@ static int st_gpiolib_register_bank(struct st_pinctrl
> *info,
>                                              gpio_irq, st_gpio_irq_handler);
>         }
>
> -       if (info->irqmux_base > 0 || gpio_irq > 0) {
> +       if (!IS_ERR(info->irqmux_base) || gpio_irq > 0) {
>                 err = gpiochip_irqchip_add(&bank->gpio_chip,
But if I am not wrong in function st_pctl_probe_dt, This is already done:

if (IS_ERR(info->irqmux_base))
            return PTR_ERR(info->irqmux_base);

That is the reason I thought there is no need to recheck the pointer
info->irqmux_base.
Am I misunderstanding something?
> &st_gpio_irqchip,
>                                            0, handle_simple_irq,
>                                            IRQ_TYPE_LEVEL_LOW);
>
>
> Thanks,
> srini
>
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-- 
Thanks and Regards
Pramod
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