linux-kernel - Re: [PATCH 2/4] media: rkisp1: Fix IRQ handler return values

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Date:   Tue, 5 Dec 2023 14:02:44 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To:     Adam Ford <aford173@...il.com>
Cc:     Dafna Hirschfeld <dafna@...tmail.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Paul Elder <paul.elder@...asonboard.com>,
        Alexander Stein <alexander.stein@...tq-group.com>,
        kieran.bingham@...asonboard.com, umang.jain@...asonboard.com,
        linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] media: rkisp1: Fix IRQ handler return values

On 05/12/2023 13:57, Adam Ford wrote:
> On Tue, Dec 5, 2023 at 2:10 AM Tomi Valkeinen
> <tomi.valkeinen@...asonboard.com> wrote:
>>
>> The IRQ handler rkisp1_isr() calls sub-handlers, all of which returns an
>> irqreturn_t value, but rkisp1_isr() ignores those values and always
>> returns IRQ_HANDLED.
>>
>> Fix this by collecting the return values, and returning IRQ_HANDLED or
>> IRQ_NONE as appropriate.
>>
>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
>> ---
>>   drivers/media/platform/rockchip/rkisp1/rkisp1-dev.c | 18 ++++++++++++++----
>>   1 file changed, 14 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/media/platform/rockchip/rkisp1/rkisp1-dev.c b/drivers/media/platform/rockchip/rkisp1/rkisp1-dev.c
>> index 76f93614b4cf..1d60f4b8bd09 100644
>> --- a/drivers/media/platform/rockchip/rkisp1/rkisp1-dev.c
>> +++ b/drivers/media/platform/rockchip/rkisp1/rkisp1-dev.c
>> @@ -445,17 +445,27 @@ static int rkisp1_entities_register(struct rkisp1_device *rkisp1)
>>
>>   static irqreturn_t rkisp1_isr(int irq, void *ctx)
>>   {
>> +       irqreturn_t ret;
>> +
>>          /*
>>           * Call rkisp1_capture_isr() first to handle the frame that
>>           * potentially completed using the current frame_sequence number before
>>           * it is potentially incremented by rkisp1_isp_isr() in the vertical
>>           * sync.
>>           */
>> -       rkisp1_capture_isr(irq, ctx);
>> -       rkisp1_isp_isr(irq, ctx);
>> -       rkisp1_csi_isr(irq, ctx);
>>
>> -       return IRQ_HANDLED;
>> +       ret = IRQ_NONE;
>> +
>> +       if (rkisp1_capture_isr(irq, ctx) == IRQ_HANDLED)
>> +               ret = IRQ_HANDLED;
>> +
>> +       if (rkisp1_isp_isr(irq, ctx) == IRQ_HANDLED)
>> +               ret = IRQ_HANDLED;
>> +
>> +       if (rkisp1_csi_isr(irq, ctx) == IRQ_HANDLED)
>> +               ret = IRQ_HANDLED;
>> +
> 
> It seems like we're throwing away the value of ret each time the
> subsequent if statement is evaluated.  Whether or not they return
> didn't matter before, and the only one that seems using the return
> code is the last one.
> 
> Wouldn't it be simpler to use ret = rkisp1_capture_isr(irq, ctx), ret
> = rkisp1_isp_isr(irq, ctx) and ret = rkisp1_csi_isr(irq, ctx) if we
> care about the return code?
> 
> How do you expect this to return if one of the first two don't return
> IRQ_HANDLED?

I'm sorry, I don't quite follow what you mean. Can you elaborate a bit?

We want the rkisp1_isr() to return IRQ_NONE if none of the sub-handlers 
handled the interrupt. Otherwise, if any of the sub-handlers return 
IRQ_HANDLED, rkisp1_isr() returns IRQ_HANDLED.

  Tomi