linux-kernel - Re: [PATCH] drm/irq: Add irq as false detection

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Date:   Mon, 2 Nov 2020 20:32:17 +0800
From:   "tiantao (H)" <tiantao6@...wei.com>
To:     Thomas Zimmermann <tzimmermann@...e.de>,
        Tian Tao <tiantao6@...ilicon.com>,
        <maarten.lankhorst@...ux.intel.com>, <mripard@...nel.org>,
        <airlied@...ux.ie>, <daniel@...ll.ch>,
        <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/irq: Add irq as false detection



在 2020/11/2 20:09, Thomas Zimmermann 写道:
> Hi
> 
> Am 02.11.20 um 12:19 schrieb Tian Tao:
>> Add the detection of false for irq, so that the EINVAL is not
>> returned when dev->irq_enabled is false.
>>
>> Signed-off-by: Tian Tao <tiantao6@...ilicon.com>
>> ---
>>   drivers/gpu/drm/drm_irq.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
>> index 09d6e9e..7537a3d 100644
>> --- a/drivers/gpu/drm/drm_irq.c
>> +++ b/drivers/gpu/drm/drm_irq.c
>> @@ -172,6 +172,9 @@ int drm_irq_uninstall(struct drm_device *dev)
>>   	bool irq_enabled;
>>   	int i;
>>   
>> +	if (!dev->irq_enabled || !dev)
>> +		return 0;
>> +
> 
> Dereferencing a pointer before NULL-checking it, is Yoda programming. :)
> I'd just drop the test for !dev and assume that dev is always valid.
> 
> I suggest to change the int return value to void and return nothing.
> 
> Re-reading the actual implementation of this function, this location
> might be too early. Further below there already is a test for
> irq_enabled. Put a drm_WARN_ON around it and it should be fine. This way
> the vblank handlers will be disabled and erroneous callers will see a
> warning in the kernel's log.
> 
thank you，I will send a new patch to fix that.
> Best regards
> Thomas
> 
>>   	irq_enabled = dev->irq_enabled;
>>   	dev->irq_enabled = false;
>>   
>>
>