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Wysocki" , Danilo Krummrich , Thierry Reding , Mikko Perttunen , David Airlie , Simona Vetter , Jonathan Hunter , linux-media@vger.kernel.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, driver-core@lists.linux.dev, dri-devel@lists.freedesktop.org, linux-tegra@vger.kernel.org, Ekansh Gupta , Dmitry Baryshkov References: <20260423-glymur-v2-0-0296bccb9f4e@oss.qualcomm.com> <20260423-glymur-v2-2-0296bccb9f4e@oss.qualcomm.com> <2026042346-trustable-register-095a@gregkh> Content-Language: en-US In-Reply-To: <2026042346-trustable-register-095a@gregkh> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-GUID: j08OWXgkRmoHZn6tEH7fTcaRyXcq_mzN X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDI0MDA5OSBTYWx0ZWRfX+12sQcZdzgxF XgMrIgLLVGZNwwWsXyxiskQvNPTN9RyU29kpTRjmymAzSIhfWcZqDhkFOQsAKVun0EdggewreIi vzi3GZ4cuPifuH4NCLw4qqBpebAjzVlYUnEknIuP8I5y2wWekUVkydANaaCtCgdAFkkOsTnmKVl dYSTy8PiwJVSJyGRPb5QyR8mAcFA8PosMkPimxltkNnwAB57hE8vxEjV7xvJaUDWq0tf/2XG4br IZ7Ej3QPqiL0QXCMJDUXcQZhezhWWj9kilLyj5XIxexxsrOLMM9jyhvESq8t9qaDtRZ0l8y5edZ d6UZnIfuO/CFEayL8PAhdA35/2INHhkHpCias6iWGt7EPaIsQ7KeUi0pEeFynlH7av8aMLpKGZs YiKTLb1RWt/MdAGTffEdLeAGyMK2aTmIvU+OVatX4boQ1wHd57/cMH7uixfWa5TwspbWsXeSuL5 EWIF86AQ4YEBVx2zgPg== X-Proofpoint-ORIG-GUID: j08OWXgkRmoHZn6tEH7fTcaRyXcq_mzN X-Authority-Analysis: v=2.4 cv=QJNYgALL c=1 sm=1 tr=0 ts=69eb4680 cx=c_pps a=mDZGXZTwRPZaeRUbqKGCBw==:117 a=K3jt3zD9TrcZs+Uyli2v9A==:17 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=_glEPmIy2e8OvE2BGh3C:22 a=VwQbUJbxAAAA:8 a=7CQSdrXTAAAA:8 a=EUspDBNiAAAA:8 a=5Qc4mBPHLNQQZN8o19QA:9 a=QEXdDO2ut3YA:10 a=zc0IvFSfCIW2DFIPzwfm:22 a=a-qgeE7W1pNrGK8U0ZQC:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-23_03,2026-04-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 phishscore=0 bulkscore=0 malwarescore=0 adultscore=0 impostorscore=0 priorityscore=1501 spamscore=0 lowpriorityscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604200000 definitions=main-2604240099 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 4/23/2026 7:07 PM, Greg Kroah-Hartman wrote: > On Thu, Apr 23, 2026 at 06:59:31PM +0530, Vishnu Reddy wrote: >> From: Ekansh Gupta >> >> When a driver needs to create virtual device at runtime and map it to >> an IOMMU context for memory isolation, there is no common bus available >> for this purpose. Each driver ends up implementing its own bus type, >> leading to duplicated logic across multiple drivers. >> >> host1x driver implemented its own bus type to attach an IOMMU context to >> a dynamically created device. The Iris VPU driver now has the same >> requirement. Rather than duplicating the same bus logic again, a shared >> bus type is introduced under drivers/base that multiple drivers can use >> directly. >> >> The bus takes care of creating a device and attaching the IOMMU context >> to it based on the client inputs. >> >> Suggested-by: Dmitry Baryshkov >> Signed-off-by: Ekansh Gupta >> Signed-off-by: Vikash Garodia >> Signed-off-by: Vishnu Reddy >> --- >> drivers/base/Kconfig | 3 ++ >> drivers/base/Makefile | 1 + >> drivers/base/dma_context_bus.c | 77 +++++++++++++++++++++++++++++++++++++++++ >> include/linux/dma_context_bus.h | 26 ++++++++++++++ >> 4 files changed, 107 insertions(+) > as you can not have a device on multiple busses at the same time, this > makes no sense to me at all. "dma context" is a bus-specific thing, so > please add it to the bus that you are wanting it for. It can't be a > generic bus as that just doesn't work. > > Or what am I missing here? > > And why is DMA somehow "special" here from any other hardware attribute? Let me give brief information which was discussed, in the initial series, the iris VPU used platform bus for dynamically created devices and we got the comment/suggestion from Robin to implement a proper bus_type with a .dma_configure callback. https://lore.kernel.org/all/02b3d0f5-f94c-43cd-93af-97cfcf7751b1@arm.com/ based on the discussion, implemented the dma_context_bus and used for iris VPU devices instead of platform bus. Here, the device have only one bus (dma_context_bus), not multiple buses. Regarding the "DMA" naming, the core operation of this bus is its .dma_configure callback, which calls of_dma_configure_id() to map the device to a corresponding IOMMU stream ID. The name "dma_context" reflects this purpose. I am open to suggestions from you or Robin or anyone else, if there is a better or preferred way to achieve this, I am happy to consider it and rework the implementation accordingly. Thanks, Vishnu Reddy. > thanks, > > greg k-h