From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id AC8FBCD3430 for ; Mon, 4 May 2026 13:53:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=D4dulbXDAwQBxDOVeAokcoekpEexPLvg83xRvBbR29I=; b=epFHk5XzO+Uk4wVXdqFNmeFK37 CaZU28igP61zZdgHzSqRwDlcsA63H3V2uVUgggz7QmnQ/dap7R3UNsnzVDvdzXTtDDfiOnUPCj6Uc iWk9x1wLjNSZdh1JUrr+M+ElPcKOc/W7IIHvXMknh5Gn1sP929z6QeGaQPi4kS5nca4E5X1auHNh0 q8KduwScrOo3nes7MUQQJ6jxLA2kcvKGT+VOWL8wvww9eve4h0ZuEJB/8cSrJebUbjP6LtIp9AIt3 xO8Z0oyp1DvTIOw9MG9Wk8R29V1IZIedYEpdH3hkwVJQV7/3g57XjJfMW8r0fOihKPuZBZy9y4UOA /aRg/XKg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wJtjS-0000000DMGm-2Dxg; Mon, 04 May 2026 13:53:10 +0000 Received: from perceval.ideasonboard.com ([213.167.242.64]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wJtjP-0000000DMEN-1qsr for linux-arm-kernel@lists.infradead.org; Mon, 04 May 2026 13:53:09 +0000 Received: from killaraus.ideasonboard.com (2001-14ba-703d-e500--2a1.rev.dnainternet.fi [IPv6:2001:14ba:703d:e500::2a1]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id F04A69C; Mon, 4 May 2026 15:52:59 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1777902780; bh=jAmwC7RoNIdGSDJJnfsMWk2C7VRG5k4+P0kWxDw9Xwc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=exN6jme3FnN7ZdO5dMT/84j58aS3PmMfbugbcsP5HQfKmXzQeMcPeaceQi3LUlvYy 14u80HmmnjNDtQbvRSMWvGlbBMYR1/5ISJlmGaTbSIFKRBeISfpeJr4m04M6OyWwT9 tIcGO430tOAc9odmsPTKtdJsFUpSNNMGDC2X6S7Q= Date: Mon, 4 May 2026 16:53:00 +0300 From: Laurent Pinchart To: Luca Ceresoli Cc: Andrzej Hajda , Neil Armstrong , Robert Foss , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Rob Clark , Dmitry Baryshkov , Abhinav Kumar , Jessica Zhang , Sean Paul , Marijn Suijten , Sumit Semwal , John Stultz , Tomi Valkeinen , Michal Simek , Hui Pu , Ian Ray , Thomas Petazzoni , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, Dmitry Baryshkov Subject: Re: [PATCH v4 01/11] drm/bridge: drm_bridge_get/put(): ignore ERR_PTR Message-ID: <20260504135300.GE1344263@killaraus.ideasonboard.com> References: <20260504-drm-bridge-alloc-getput-panel_or_bridge-v4-0-b578c3daaf10@bootlin.com> <20260504-drm-bridge-alloc-getput-panel_or_bridge-v4-1-b578c3daaf10@bootlin.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260504-drm-bridge-alloc-getput-panel_or_bridge-v4-1-b578c3daaf10@bootlin.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260504_065307_618708_1CABBA27 X-CRM114-Status: GOOD ( 20.69 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, May 04, 2026 at 12:45:04PM +0200, Luca Ceresoli wrote: > Most functions returning a struct drm_bridge pointer currently return a > valid pointer or NULL, but this restricts their ability to return an error > code describing the error kind. > > In preparation to have new APIs that can return a struct drm_bridge pointer > holding an ERR_PTR (and for those which already do) make drm_bridge_get() > and drm_bridge_put() ignore ERR_PTR values, just like they ignore NULL > pointers. The change in drm_bridge_put() looks good to me. I'm less sure about drm_bridge_get(), is there a valid use case to call get() on a bridge that is not valid ? Doesn't it indicate a clear error in the caller ? > This will avoid annoying error checking in many places and the risk of > missing error checks. > > Suggested-by: Laurent Pinchart > Link: https://lore.kernel.org/all/20260318152533.GA633439@killaraus.ideasonboard.com/ > Suggested-by: Dmitry Baryshkov > Link: https://lore.kernel.org/all/omlnswxukeqgnatzdvooaashgkfcacjevkvbkm6xt33itgua2k@jcmzll2w6kdq/ > Reviewed-by: Dmitry Baryshkov > Signed-off-by: Luca Ceresoli > --- > > Changes in v4: > - removed incorrect change to drm_bridge_clear_and_put() kdoc > > Patch added in v2 > --- > drivers/gpu/drm/drm_bridge.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c > index d4b3478258ec..6fb71de6d22a 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; if NULL this function does nothing > + * @bridge: DRM bridge; if NULL or an ERR_PTR this function does nothing > * > * This function increments the bridge's refcount. > * > @@ -291,7 +291,7 @@ static void __drm_bridge_free(struct kref *kref) > */ > struct drm_bridge *drm_bridge_get(struct drm_bridge *bridge) > { > - if (bridge) > + if (!IS_ERR_OR_NULL(bridge)) > kref_get(&bridge->refcount); > > return bridge; > @@ -300,7 +300,7 @@ EXPORT_SYMBOL(drm_bridge_get); > > /** > * drm_bridge_put - Release a bridge reference > - * @bridge: DRM bridge; if NULL this function does nothing > + * @bridge: DRM bridge; if NULL or an ERR_PTR this function does nothing > * > * This function decrements the bridge's reference count and frees the > * object if the reference count drops to zero. > @@ -310,7 +310,7 @@ EXPORT_SYMBOL(drm_bridge_get); > */ > void drm_bridge_put(struct drm_bridge *bridge) > { > - if (bridge) > + if (!IS_ERR_OR_NULL(bridge)) > kref_put(&bridge->refcount, __drm_bridge_free); > } > EXPORT_SYMBOL(drm_bridge_put); -- Regards, Laurent Pinchart