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Thu, 12 Nov 2026 03:08:54 +0000 Date: Thu, 12 Nov 2026 11:13:49 +0800 From: Peng Fan To: Frank Li Cc: Frank Li , Vinod Koul , "Joerg Roedel (AMD)" , Will Deacon , Robin Murphy , Laxman Dewangan , Jon Hunter , Thierry Reding , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Frank Li , Larisa IIeana Grigore , imx@lists.linux.dev, dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, linux-tegra@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Peng Fan Subject: Re: [PATCH v5 2/7] dmaengine: add a bus for DMA channel devices Message-ID: References: <20261111-edma-iommu-v3-v5-0-2537cebe6ca2@nxp.com> <20261111-edma-iommu-v3-v5-2-2537cebe6ca2@nxp.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: JH0PR01CA0186.apcprd01.prod.exchangelabs.com (2603:1096:990:75::11) To AM8PR04MB7874.eurprd04.prod.outlook.com (2603:10a6:20b:24d::9) X-Archived-By: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: AM8PR04MB7874:EE_|DBBPR04MB7658:EE_ X-MS-Office365-Filtering-Correlation-Id: ebe6d7a9-4838-4a8f-1e59-08df406a4868 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|19092799006|376014|7416014|366016|23010399003|1800799024|22082099003|18002099003|6133799003|261009223027099003|5023799004|261102123227099003|56012099006|11063799006|4143699003|261026121527099003|261021121427099003|261022075727099003|261021123027099003|10067099003; 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Maybe already block for >> >long time. >> >> In drivers/dma/tegra186-gpc-dma.c: >> 1543 if (use_iommu_map) { >> 1544 chdev->bus = pdev->dev.bus; >> >> I used similar method, but Sashiko spotted issue for v1 [1], we have to >> add a new bus to handle it. >> >> " >> Does this illegally modify the bus type of an already-registered device? >> >> This is executed after dmaenginem_async_device_register() has already called >> device_add(). Since bus_add_device() is never executed, won't device_del() >> invoke bus_remove_device() during driver unbinding or removal, causing a fatal >> reference count underflow and use-after-free on the global platform_bus_type >> subsystem? >> " >> >> [1] https://lore.kernel.org/dmaengine/20260916160608.099201F000FF@smtp.kernel.org/ > >Can you add it to commit message to know why need add new bus type ok. Update in V6. Thanks Peng > >Frank > >> >> Thanks >> Peng >> >> > >> >Frank >> > >> >> +#endif >> >> + >> >> /** >> >> * enum dma_slave_buswidth - defines bus width of the DMA slave >> >> * device, source or target buses >> >> >> >> -- >> >> 2.34.1 >> >> >> > > >