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Thu, 17 Oct 2019 10:21:03 +0000 From: "james qian wang (Arm Technology China)" To: Brian Starkey CC: Mihail Atanassov , "dri-devel@lists.freedesktop.org" , David Airlie , Liviu Dudau , Russell King , Maxime Ripard , "linux-kernel@vger.kernel.org" , nd , Sean Paul Subject: Re: [RFC,3/3] drm/komeda: Allow non-component drm_bridge only endpoints Thread-Topic: [RFC,3/3] drm/komeda: Allow non-component drm_bridge only endpoints Thread-Index: AQHVfmX7+sBzYHhR8EiYyRUjNjETp6dddmWAgAAIg4CAALRsAIAAV3gAgAAhhoA= Date: Thu, 17 Oct 2019 10:21:03 +0000 Message-ID: <20191017102055.GA8308@jamwan02-TSP300> References: <20191004143418.53039-4-mihail.atanassov@arm.com> <20191009055407.GA3082@jamwan02-TSP300> <5390495.Gzyn2rW8Nj@e123338-lin> <20191016162206.u2yo37rtqwou4oep@DESKTOP-E1NTVVP.localdomain> <20191017030752.GA3109@jamwan02-TSP300> <20191017082043.bpiuvfr3r4jngxtu@DESKTOP-E1NTVVP.localdomain> In-Reply-To: <20191017082043.bpiuvfr3r4jngxtu@DESKTOP-E1NTVVP.localdomain> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: user-agent: Mutt/1.10.1 (2018-07-13) x-originating-ip: [113.29.88.7] x-clientproxiedby: HK2PR02CA0182.apcprd02.prod.outlook.com (2603:1096:201:21::18) To VE1PR08MB5006.eurprd08.prod.outlook.com (2603:10a6:803:113::31) Authentication-Results-Original: spf=none (sender IP is ) smtp.mailfrom=james.qian.wang@arm.com; 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X-MS-Office365-Filtering-Correlation-Id-Prvs: ae12bc4e-ea00-44a1-5cab-08d752ebb68f NoDisclaimer: True X-Forefront-PRVS: 01930B2BA8 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: GVRBU404rkusf/C2alU4hOPW8I6OYxHWepVZ4KYyUtPVWq3ZiSeR7jLdWF++5K7sencW54O2osEP01ATNO34E9e7HBdJ1g+qmC9QeEPsUAj+CkI+TAq2bbBOCGxmoN3no28bSi/97Cdc/KTxeV3fA51BgJnCeTuU4MWobEuxJ1M96PuyX4p+0TcrcAmUc7X1QXnDcGa4x6TiC18+FDrK75Ei++9apq2OIHcC2U9Qge6T5VTPlyVLNutwj5+qVDpbapA1tMlwtou311SGGAnVIizCdF3+vOFGdluDVS9bFSpcYKyIrzmlYAdG39Tax6fTY0dGzf1Rgk7w4dWMYuOpVaYlEVcWolC7CD9v7/9Ky7RMg3M9wtYizNwT2tarYmhAzZRBDN1UQzmxZSvA6klIL3SGwVd1eaP17/alg5fsYSo= X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Oct 2019 10:21:15.7919 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: db8a6219-6ed8-4069-f3e5-08d752ebbe41 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[63.35.35.123];Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM6PR08MB3624 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 17, 2019 at 08:20:56AM +0000, Brian Starkey wrote: > On Thu, Oct 17, 2019 at 03:07:59AM +0000, james qian wang (Arm Technology= China) wrote: > > On Wed, Oct 16, 2019 at 04:22:07PM +0000, Brian Starkey wrote: > > >=20 > > > If James is strongly against merging this, maybe we just swap > > > wholesale to bridge? But for me, the pragmatic approach would be this > > > stop-gap. > > > > >=20 > > This is a good idea, and I vote +ULONG_MAX :) > >=20 > > and I also checked tda998x driver, it supports bridge. so swap the > > wholesale to brige is perfect. :) > >=20 >=20 > Well, as Mihail wrote, it's definitely not perfect. >=20 > Today, if you rmmod tda998x with the DPU driver still loaded, > everything will be unbound gracefully. >=20 > If we swap to bridge, then rmmod'ing tda998x (or any other bridge > driver the DPU is using) with the DPU driver still loaded will result > in a crash. I haven't read the bridge code, but seems this is a bug of drm_bridge, since if the bridge is still in using by others, the rmmod should fail And personally opinion, if the bridge doesn't handle the dependence. for us: - add such support to bridge or - just do the insmod/rmmod in correct order. > So, there really are proper benefits to sticking with the component > code for tda998x, which is why I'd like to understand why you're so > against this patch? > This change handles two different connectors in komeda internally, compare with one interface, it increases the complexity, more risk of bug and more cost of maintainance. So my suggestion is keeping on one single interface in komeda, no matter it is bridge or component, but I'd like it only one, but not them both in komeda. Thanks James > Thanks, > -Brian