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Received: from AM7PR04MB7046.eurprd04.prod.outlook.com (2603:10a6:20b:113::22) by AS8PR04MB7526.eurprd04.prod.outlook.com (2603:10a6:20b:299::23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9745.22; Thu, 26 Mar 2026 09:35:19 +0000 Received: from AM7PR04MB7046.eurprd04.prod.outlook.com ([fe80::4609:64af:8a4b:fd64]) by AM7PR04MB7046.eurprd04.prod.outlook.com ([fe80::4609:64af:8a4b:fd64%3]) with mapi id 15.20.9745.019; Thu, 26 Mar 2026 09:35:19 +0000 Message-ID: <6d2e9c83-8652-427f-869a-20f7353f126a@nxp.com> Date: Thu, 26 Mar 2026 17:36:30 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RESEND] drm/bridge: drm_bridge_get/put(): document NULL pointer behaviour To: Luca Ceresoli , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter Cc: Hui Pu , Ian Ray , Thomas Petazzoni , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20260324-drm-bridge-alloc-getput-document-null-check-v1-1-fb0877c49d7e@bootlin.com> From: Liu Ying Content-Language: en-US In-Reply-To: <20260324-drm-bridge-alloc-getput-document-null-check-v1-1-fb0877c49d7e@bootlin.com> Content-Type: text/plain; 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However it's not documented, so it's not clear whether it is > part of the API "contract" or just a current implementation detail that > might change in the future. > > There is no visible reason to remove this NULL check, so document it, > making it part of the contract, letting users count on it. > > Signed-off-by: Luca Ceresoli > --- > Historical note: I thought this was documented from the beginning and > realized it's not the case when someone proposed adding a 'if (bridge) > drm_bridge_put(bridge)' to a driver [0]. Let's fix it now. > > [0] https://lore.kernel.org/lkml/DG0CHD0TAH9A.27UW4KKY2O9V7@bootlin.com/ > --- > drivers/gpu/drm/drm_bridge.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c > index 3b165a0d1e77..3108249a63cd 100644 > --- a/drivers/gpu/drm/drm_bridge.c > +++ b/drivers/gpu/drm/drm_bridge.c > @@ -282,7 +282,7 @@ static void __drm_bridge_free(struct kref *kref) > > /** > * drm_bridge_get - Acquire a bridge reference > - * @bridge: DRM bridge > + * @bridge: DRM bridge; if NULL this function does nothing > * > * This function increments the bridge's refcount. > * > @@ -300,7 +300,7 @@ EXPORT_SYMBOL(drm_bridge_get); > > /** > * drm_bridge_put - Release a bridge reference > - * @bridge: DRM bridge > + * @bridge: DRM bridge; if NULL this function does nothing So, we can drop the if(_T) check for cleanup action, right? DEFINE_FREE(drm_bridge_put, struct drm_bridge *, if (_T) drm_bridge_put(_T)) Reviewed-by: Liu Ying > * > * This function decrements the bridge's reference count and frees the > * object if the reference count drops to zero. > > --- > base-commit: a50007089e078a1b7a826559a02277b1601ee189 > change-id: 20260129-drm-bridge-alloc-getput-document-null-check-a551e64b8fc1 > > Best regards, -- Regards, Liu Ying