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[2001:1c00:c32:7800:5bfa:a036:83f0:f9ec]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b8dbf1847f9sm1064954166b.42.2026.02.03.06.19.13 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 03 Feb 2026 06:19:14 -0800 (PST) Message-ID: Date: Tue, 3 Feb 2026 15:19:13 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: johannes.goede@oss.qualcomm.com Subject: Re: [RFC PATCH v2] media: Virtual camera driver To: Jani Nikula , Jarkko Sakkinen , linux-media@vger.kernel.org Cc: anisse@astier.eu, oleksandr@natalenko.name, linux-integrity@vger.kernel.org, Mauro Carvalho Chehab , Hans Verkuil , Laurent Pinchart , Sakari Ailus , Jacopo Mondi , Ricardo Ribalda , open list References: <20260202204425.2614054-1-jarkko@kernel.org> <6b192c71-c389-4a6e-b7c3-ddcd5cc4aa34@oss.qualcomm.com> <37a0d91c2e78c97f3d956444c4f7a2a2fca9ae06@intel.com> Content-Language: en-US, nl In-Reply-To: <37a0d91c2e78c97f3d956444c4f7a2a2fca9ae06@intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjAzMDExNCBTYWx0ZWRfX35pbJ5vjCHlQ 91GS3A0mG9okvoRZJJqBmQtiWSRN1tSBKzOubKjLZQa7tNkuifXONjcTwCbARlEq7tz+PQfeFoW 7LBie0OGjAouyKvJA+LeVChXNNGIKBuzQ8caK4alRbuyjLuPpjz+lrFmZE2e7kHBbSqP2qnyhxb le1QeDBxICQuVheP8kn78sETqWAjm4tjvIFMmknm9q59GpGNGQ0v2JunNGgBdlKSIq50Yq+ZG/N 7cyJKKgSVJcMMQVNqj9MQRWZapmj0vWQlErktLf0pt+w8W1cdF/HnMTMjUoDlzaRr+JWgCtMcfD GuLGO72GAe+Q2JKV9s2tAqmFOeM0Pr2mbrjdWnTl+KkAnXCRj/6mKEIMPHd1LVbfaB0RWd0XRTE uuNhFTb/oT5SBI26Fxiqjb1lzVYh/sVJDOrtMRIWJ6d6SOPcJyy2/rTbszNxVnKVjSqVp8avwst qX0G7JjaOHjV8R4MvHw== X-Authority-Analysis: v=2.4 cv=XfOEDY55 c=1 sm=1 tr=0 ts=698203e5 cx=c_pps a=qKBjSQ1v91RyAK45QCPf5w==:117 a=xqWC_Br6kY4A:10 a=IkcTkHD0fZMA:10 a=HzLeVaNsDn8A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=NEAV23lmAAAA:8 a=EUspDBNiAAAA:8 a=E8RJ7uGaLTfD5B8v_isA:9 a=QEXdDO2ut3YA:10 a=NFOGd7dJGGMPyQGDc5-O:22 X-Proofpoint-ORIG-GUID: X4EVM7WzftiiIWvGNc2xMW9FO3uVBf-V X-Proofpoint-GUID: X4EVM7WzftiiIWvGNc2xMW9FO3uVBf-V X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-02-03_04,2026-02-02_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 spamscore=0 phishscore=0 adultscore=0 priorityscore=1501 lowpriorityscore=0 impostorscore=0 suspectscore=0 malwarescore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2602030114 Hi Jani, On 3-Feb-26 14:20, Jani Nikula wrote: > On Tue, 03 Feb 2026, johannes.goede@oss.qualcomm.com wrote: >> The problem is that what you're suggesting is basically a much >> improved (using dma-buf is way better) v4l2-loopback driver and >> v4l2-loopback has been blocked from getting merged into the kernel >> because besides the mobile-phone camera use, the other main use-case >> is to allow running proprietary camera stacks like Intel's proprietary >> camerastack and then presenting that to userspace as a standard v4l2 >> cam so that userspace apps will just work. > > ... > >> The community concensus is that the solution here is for apps to >> access cameras through pipewire. Together with the shift of laptops >> cameras from UVC to "raw" MIPI cameras there also is a shift to >> running applications sandboxed as flatpacks because of the changing >> "cyber" security landscape. This is why pipewire was chosen because >> it also solves the accessing cameras from a sandbox issue. > > Why is v4l2-loopback problematic from the perspective of facilitating > running proprietary camera stacks, but pipewire isn't? Once pipewire mostly works everywhere for camera access then indeed this will allow proprietary stacks to present themselves as a pipewire src. For now though most proprietary stacks seem to prefer v4l2loopback because pipewire is not supported as camera source yet by a lot of apps. As I indicated in my original email personally I'm a bit divided on whether a virtual camera driver should be kept out of the kernel to not promote proprietary userspace stacks, but this is not my call. OTHO evdi: https://github.com/DisplayLink/evdi has been kept out of the kernel for pretty much the same reasons by the drm/kms folks. At least AFAIK there still is no way to present virtual kms capable display outputs backed by userspace in the kernel. I completely understand where you're coming from wrt v4l2-loopback support (or something equivalent) but asking for this really is the same as asking for the evdi driver to get merged, which AFAIK has been blocked for the reason of avoiding proprietary userspace display output drivers (I guess there might be technical reasons too). Regards, Hans