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Wed, 15 Apr 2026 10:34:35 -0700 (PDT) X-Received: by 2002:a17:902:6949:b0:2b2:b117:1e16 with SMTP id d9443c01a7336-2b2d5a459ffmr160044375ad.20.1776274475300; Wed, 15 Apr 2026 10:34:35 -0700 (PDT) Received: from [10.206.105.200] ([202.46.23.25]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b47810b70csm25397215ad.23.2026.04.15.10.34.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 15 Apr 2026 10:34:34 -0700 (PDT) Message-ID: Date: Wed, 15 Apr 2026 23:04:26 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.8.0 Subject: Re: [PATCH 1/3] drivers: base: Add generic context device bus Content-Language: en-US To: Greg Kroah-Hartman , ekansh.gupta@oss.qualcomm.com Cc: "Rafael J. Wysocki" , Danilo Krummrich , Thierry Reding , Mikko Perttunen , David Airlie , Simona Vetter , Joerg Roedel , Will Deacon , Robin Murphy , Arnd Bergmann , Srinivas Kandagatla , Dmitry Baryshkov , Bharath Kumar , Chenna Kesava Raju , linux-kernel@vger.kernel.org, driver-core@lists.linux.dev, dri-devel@lists.freedesktop.org, linux-tegra@vger.kernel.org, iommu@lists.linux.dev, linux-arm-msm@vger.kernel.org, Vikash Garodia References: <20260414-computebus-v1-0-4d904d40926a@oss.qualcomm.com> <20260414-computebus-v1-1-4d904d40926a@oss.qualcomm.com> <2026041418-volley-composer-6363@gregkh> From: Vishnu Reddy In-Reply-To: <2026041418-volley-composer-6363@gregkh> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Proofpoint-GUID: oEOn8NcnCRhLszrIsASaNob-gHuySp1E X-Authority-Analysis: v=2.4 cv=eLMjSnp1 c=1 sm=1 tr=0 ts=69dfcc2c cx=c_pps a=IZJwPbhc+fLeJZngyXXI0A==:117 a=ZePRamnt/+rB5gQjfz0u9A==:17 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=yOCtJkima9RkubShWh1s:22 a=EUspDBNiAAAA:8 a=xRG3GzwA0ZaNjhFdG0MA:9 a=QEXdDO2ut3YA:10 a=uG9DUKGECoFWVXl0Dc02:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDE1MDE2MyBTYWx0ZWRfX5K2ZCRnDwmaP bCMumQ05DHkTVsHZ9KRM1AF8TRYd9GzYQv6k76G4gZq48TnyQJ5NUwIKKv+TduvInyUEUtTjGCS rUxS70XhU2ufrRy7RCYk3q7Gz76+d2GIjMvLGa2tgUjh7IrdK5h5oo5ADJ+RCi30KfR+3ac44Rp tjXR2H4Nv3rlyAd3VyCM3k7XgE7xnUGTtQVICuojxBfl87sjMQYWGrCvakYtWUSIoO7jOyUyIIK jUWdKYTqcIe0QVhLsWPjXHtI/criBYMV4SZytw1ZdE83ZsLcsVKVNL6yU8zQmWLgEyOeDuQ6863 P5k1ob/NFUKo5kJn/wdsz3mySM8qWqs1THDPAAsYS3ouxPKXuL1ZL5OuBqK5o4lJMAb4Tx2EMTJ +yMwBqR4zmNy9+ZlvOlYHZttJd7xSwB9wiIaMDfHoLqdGIS/vtEAZDdtTjMTCjTpwVPXwCmFfke 1TNOhudByrQ8cBmQMGA== X-Proofpoint-ORIG-GUID: oEOn8NcnCRhLszrIsASaNob-gHuySp1E 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=2026-04-15_01,2026-04-13_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 clxscore=1015 bulkscore=0 lowpriorityscore=0 impostorscore=0 suspectscore=0 malwarescore=0 priorityscore=1501 spamscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604070000 definitions=main-2604150163 On 4/14/2026 10:19 PM, Greg Kroah-Hartman wrote: > On Tue, Apr 14, 2026 at 10:01:15PM +0530, Ekansh Gupta via B4 Relay wrote: >> From: Ekansh Gupta >> >> Introduce a new generic bus type for synthetic context bank devices >> that require IOMMU context isolation. This bus provides a shared >> infrastructure for accelerator and GPU drivers that create virtual >> devices representing IOMMU context banks. >> >> Currently, drivers like host1x implement their own bus types for >> context devices. This generic implementation allows multiple drivers >> to share the same bus infrastructure, simplifying the IOMMU subsystem >> integration and reducing code duplication. >> >> Signed-off-by: Ekansh Gupta >> --- >> drivers/base/Kconfig | 3 +++ >> drivers/base/Makefile | 1 + >> drivers/base/context_bus.c | 24 ++++++++++++++++++++++++ >> include/linux/context_bus.h | 15 +++++++++++++++ >> 4 files changed, 43 insertions(+) >> >> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig >> index f7d385cbd3ba..479bc4bb442b 100644 >> --- a/drivers/base/Kconfig >> +++ b/drivers/base/Kconfig >> @@ -4,6 +4,9 @@ menu "Generic Driver Options" >> config AUXILIARY_BUS >> bool >> >> +config CONTEXT_DEVICE_BUS >> + bool > > So this is a context-free bus? I.e. no documentation? > > :) > > This feels really odd, this "bus" isn't doing anything at all. So why > do you need it and can't use auxbus or faux? Looks like the device have specific iommu configuration (via of_dma_configure()), then using the auxbus or faux bus types does not have the bus notifier calls to iommu_release_device(). Please correct me if I misunderstood? > > You say something about an iommu, but yet this has no information about > an iommu at all, so why are they somehow special? > > You need to provide a lot more information here, sorry. > > greg k-h > >