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Fri, 23 Oct 2026 06:01:34 -0700 (PDT) Received: from localhost ([140.209.217.211]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a29cdb75cfsm3940865e9.9.2026.10.23.06.01.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Oct 2026 06:01:34 -0700 (PDT) Date: Fri, 23 Oct 2026 15:01:30 +0200 From: Jiri Pirko To: Jason Gunthorpe Cc: linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, david.quigley@intel.com, lukas@wunner.de, ksinyuk@kernel.org, rodrigo.vivi@intel.com, cedric.xing@intel.com, sameo@meta.com, drdeeglaze@gmail.com, James.Bottomley@hansenpartnership.com, aik@amd.com, jpiotrowski@nvidia.com, qinkun@google.com, pgonda@google.com, jic23@kernel.org, alistair.francis@wdc.com, ankita@nvidia.com, suzuki.poulose@arm.com, kas@kernel.org, rick.p.edgecombe@intel.com, elena.reshetova@intel.com, dave.hansen@linux.intel.com, sathyanarayanan.kuppuswamy@linux.intel.com, peter.fang@intel.com Subject: Re: [PATCH RFC 13/20] Documentation: ctlv: Describe how to write a family Message-ID: References: <20261015145053.3664509-1-jiri@resnulli.us> <20261015145053.3664509-14-jiri@resnulli.us> <179245258505.58760.3972297562218204862.b4-review@b4> <20261021144951.GR3008132@nvidia.com> <20261021164857.GT3008132@nvidia.com> <20261022192118.GC3746973@nvidia.com> X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261022192118.GC3746973@nvidia.com> Thu, Oct 22, 2026 at 09:21:18PM +0200, jgg@nvidia.com wrote: >On Thu, Oct 22, 2026 at 10:22:55AM +0200, Jiri Pirko wrote: > >> >But it does work well here, and matches what rdma and fwctl did as >> >well. So maybe iommufd is weird. >> >> Well, one CTLV chardev is always backed by one device. I think this 1:1 >> mapping is clear in the device model. Iommufd indeed looks weird in this >> matter. > >iommufd doesn't do 1:1 with a device.. > >It is more like netlink where it talks to all the devices in the >system concurrently. > >> >> Depends on the user/subsystem. Either families_dump op could be used of >> >> udev uvevents that also carry family inheritance chain: >> >> CTLV_FAMILY=ctlv-attestation-tdx >> >> CTLV_COMPATIBLE_0=ctlv >> >> CTLV_COMPATIBLE_1=ctlv-attestation >> >> CTLV_COMPATIBLE_2=ctlv-attestation-tdx >> >> CTLV_COMPATIBLE_N=3 >> > >> >I wouldn't try to link it to udev either, by the time some userspace >> >uses the cdev the udev information is gone, and may be unreachable >> >from inside a container or similar.. >> >> This just gives possibility for udev to work properly. Depends on >> the user/usecase if it's going to be used or not. Not sure what you mean >> by "udev information is gone". Udev might use these uevent info to do >> aliases, similar to dev/disk/by-* > >I don't know if you can encode N compatible strings into a file name. Yeah, the udev rule would have to have some logic on top of them, sure. > >And in a container or something you can't get the uevent, so no client >software could rely on this information. Okay. > >Jason