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Thu, 22 Oct 2026 00:24:18 -0700 (PDT) Date: Thu, 22 Oct 2026 03:24:15 -0400 From: "Michael S. Tsirkin" To: Demi Marie Obenour Cc: Cornelia Huck , Peter Hilber , virtio-comment@lists.linux.dev, Jan Kiszka , Stefan Hajnoczi , Trilok Soni Subject: Re: [PATCH v2] content: Reserve ID 52 for QPSFI device Message-ID: <20261022032118-mutt-send-email-mst@kernel.org> References: <20261021180031.7175-1-peter.hilber@oss.qualcomm.com> <20261021154801-mutt-send-email-mst@kernel.org> <87mrs62vzj.fsf@redhat.com> <26e6efbe-abc0-452d-a682-611cf91e41b8@gmail.com> X-Mailing-List: virtio-comment@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 In-Reply-To: <26e6efbe-abc0-452d-a682-611cf91e41b8@gmail.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: bqKYGIB2x948fiNbwAFurmVkfcry_KOpHQVBMvY5fkY_1792653860 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Thu, Oct 22, 2026 at 03:07:41AM -0400, Demi Marie Obenour wrote: > On 10/22/26 00:35, Cornelia Huck wrote: > > On Wed, Oct 21 2026, "Michael S. Tsirkin" wrote: > > > >> On Wed, Oct 21, 2026 at 03:25:31PM -0400, Demi Marie Obenour wrote: > >>> On 10/21/26 14:00, Peter Hilber wrote: > >>>> Reserve a device ID for QPSFI devices (Qualcomm Platform Subsystem > >>>> Firmware Interface). QPSFI devices expose functionality across SoC > >>>> subsystems through a common Virtio-based protocol. There are no plans to > >>>> standardize the devices. > >>>> > >>>> The Linux DCP display driver series is planned as the first user of this > >>>> device ID: > >>>> > >>>> https://lore.kernel.org/all/20261015-jshekhar-drm-msm-dcp-v1-v1-10-48aad0fe4f72@oss.qualcomm.com/ > >>>> > >>>> Device ID 51 is already reserved for the Virtio HAB device: > >>>> > >>>> https://lore.kernel.org/virtio-comment/20260702140939.3535968-1-zeloren@qti.qualcomm.com/ > >>>> > >>>> Signed-off-by: Peter Hilber > >>>> --- > >>>> > >>>> v2: > >>>> > >>>> - Rename the device from "Snapdragon device" to "QPSFI device". > >>>> > >>>> - Refer to DCP Linux driver patch as planned first QPSFI user. > >>>> > >>>> v1: > >>>> > >>>> - Was posted as "content: Reserve ID 52 for Snapdragon device": > >>>> > >>>> https://lore.kernel.org/virtio-comment/20260826115504.1955-1-peter.hilber@oss.qualcomm.com/ > >>>> > >>>> content.tex | 2 ++ > >>>> 1 file changed, 2 insertions(+) > >>>> > >>>> diff --git a/content.tex b/content.tex > >>>> index 243ce2dde36b..7416939e67d3 100644 > >>>> --- a/content.tex > >>>> +++ b/content.tex > >>>> @@ -805,6 +805,8 @@ \chapter{Device Types}\label{sec:Device Types} > >>>> \hline > >>>> 50 & Video encoder/decoder device \\ > >>>> \hline > >>>> +52 & QPSFI device \\ > >>>> +\hline > >>>> \end{longtable} > >>>> > >>>> Some of the devices above are unspecified by this document, > >>> > >>> I think it would be best to have a single ID for vendor-specific devices. > >>> I believe most of the ID space has already been used, at least for virtio-PCI. > >>> -- > >>> Sincerely, > >>> Demi Marie Obenour (she/her/hers) > >> > >> Sounds like a good idea to me. And then qualcomm can do what they > >> want, like check subsystem id for pci or whatever? > >> Only issue is there is no way to distinguish for mmio/ccw. > >> Maybe, add vendor specific id as first e.g. 8 bytes ro in the config space? > >> Peter? > > > > Using some information in the config space looks like the most flexible > > way to me. Are we still happy with how the device ids are organized in > > general (i.e. when do we want a new one, and when do we want to extend > > an existing device?) > > For a platform device like this, I'd prefer to pass the information out > of band. After all, this device will only ever be found on Qualcomm > SoCs, and presumably the kernel knows exactly which PCI device is > supposed to be the QPSFI device. This means that the kernel can just > special-case it. Yes but we are discussing making this id a general "vendor specific device", as opposed to a "qualcomm device". Could you share, e.g. if this device has config space, and whether reading X bytes at offset 0 of this device is harmless, for some value of X? > Would it make sense to put this in the ACPI tables or device tree? As long as it's vendor specific. > -- > Sincerely, > Demi Marie Obenour (she/her/hers)