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Subject: Re: [PATCH] drm/irq: Add irq as false detection
To:     Thomas Zimmermann <tzimmermann@suse.de>,
        Tian Tao <tiantao6@hisilicon.com>,
        <maarten.lankhorst@linux.intel.com>, <mripard@kernel.org>,
        <airlied@linux.ie>, <daniel@ffwll.ch>,
        <dri-devel@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>
References: <1604315990-56787-1-git-send-email-tiantao6@hisilicon.com>
 <8a76d144-f8ba-bbbc-9177-53088f6dc73a@suse.de>
From:   "tiantao (H)" <tiantao6@huawei.com>
Message-ID: <d67b75bd-205b-262b-db07-36497c941731@huawei.com>
Date:   Mon, 2 Nov 2020 20:32:17 +0800
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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@hisilicon.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;
>>   
>>
>