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To:     "tiantao (H)" <tiantao6@huawei.com>,
        Tian Tao <tiantao6@hisilicon.com>, airlied@linux.ie,
        daniel@ffwll.ch, kraxel@redhat.com, alexander.deucher@amd.com,
        tglx@linutronix.de, dri-devel@lists.freedesktop.org,
        xinliang.liu@linaro.org, linux-kernel@vger.kernel.org
References: <1604050046-64539-1-git-send-email-tiantao6@hisilicon.com>
 <2dbbbad0-53cf-52cc-3b6b-0d1547f7e085@suse.de>
 <f41cbcb3-d08a-7d3f-530c-a0cb3f9e3801@huawei.com>
From:   Thomas Zimmermann <tzimmermann@suse.de>
Subject: Re: [PATCH] drm/hisilicon: Remove redundant null check
Message-ID: <b3656895-42a5-ff20-a695-dccaf1992938@suse.de>
Date:   Mon, 2 Nov 2020 10:03:39 +0100
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From: Thomas Zimmermann <tzimmermann@suse.de>
To: "tiantao (H)" <tiantao6@huawei.com>, Tian Tao <tiantao6@hisilicon.com>,
 airlied@linux.ie, daniel@ffwll.ch, kraxel@redhat.com,
 alexander.deucher@amd.com, tglx@linutronix.de,
 dri-devel@lists.freedesktop.org, xinliang.liu@linaro.org,
 linux-kernel@vger.kernel.org
Message-ID: <b3656895-42a5-ff20-a695-dccaf1992938@suse.de>
Subject: Re: [PATCH] drm/hisilicon: Remove redundant null check
References: <1604050046-64539-1-git-send-email-tiantao6@hisilicon.com>
 <2dbbbad0-53cf-52cc-3b6b-0d1547f7e085@suse.de>
 <f41cbcb3-d08a-7d3f-530c-a0cb3f9e3801@huawei.com>
In-Reply-To: <f41cbcb3-d08a-7d3f-530c-a0cb3f9e3801@huawei.com>

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Hi

Am 02.11.20 um 09:46 schrieb tiantao (H):
>=20
>=20
> =E5=9C=A8 2020/11/2 16:32, Thomas Zimmermann =E5=86=99=E9=81=93:
>> Hi
>>
>> Am 30.10.20 um 10:27 schrieb Tian Tao:
>>> drm_irq_uninstall can handle the case where dev->irq_enable is false,=

>>> so Remove redundant null check.
>>>
>>> Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
>>> ---
>>> =C2=A0 drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c | 6 +++---
>>> =C2=A0 1 file changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
>>> b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
>>> index 0c1b40d..b71589b1 100644
>>> --- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
>>> +++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c
>>> @@ -246,13 +246,13 @@ static int hibmc_unload(struct drm_device *dev)=

>>> =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 drm_atomic_helper_shutdown(dev)=
;
>>> =C2=A0 -=C2=A0=C2=A0=C2=A0 if (dev->irq_enabled)
>>> -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 drm_irq_uninstall(dev);
>>> -
>>> +=C2=A0=C2=A0=C2=A0 drm_irq_uninstall(dev);
>>
>> Removing this check would at least result in an error, [1] so rather
>> leave it in for now.
>>
> Now there seems to be no driver to check the return value of
> drm_irq_uninstall

True. No clean-up code should ever fail. But currently, it's not handled
by drm_irq_uninstall().

A better fix would be to have drm_irq_uninstall() return early with a
warning if IRQs are disabled. And for most drivers, a managed version of
drm_irq_install() would be useful.

Best regards
Thomas

>> Instead, we could discuss if drm_irq_install() should become a managed=

>> interface.
>=20
> Codes like the following
> diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> index 09d6e9e..572357c 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)
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 bool irq_enabled;
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 int i;
>=20
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if(!dev->irq_enabled || !dev)
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0 return 0;
>=20
>>
>> Best regards
>> Thomas
>>
>> [1]
>> https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/drm_irq=
=2Ec#L201
>>
>>
>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 pci_disable_msi(dev->pdev);
>>> +
>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 hibmc_kms_fini(priv);
>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 hibmc_mm_fini(priv);
>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 dev->dev_private =3D NULL;
>>> +
>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return 0;
>>> =C2=A0 }
>>> =C2=A0
>>
>=20

--=20
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 N=C3=BCrnberg, Germany
(HRB 36809, AG N=C3=BCrnberg)
Gesch=C3=A4ftsf=C3=BChrer: Felix Imend=C3=B6rffer

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