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Ricardo Ribalda 37914cef17 media: uvcvideo: Create an ID namespace for streaming output terminals 
[ Upstream commit 3d9f32e02c ]

Some devices, such as the Grandstream GUV3100 and the LSK Meeting Eye
for Business & Home, exhibit entity ID collisions between units and
streaming output terminals.

The UVC specification requires unit and terminal IDs to be unique, and
uses the ID to reference entities:

- In control requests, to identify the target entity
- In the UVC units and terminals descriptors' bSourceID field, to
  identify source entities
- In the UVC input header descriptor's bTerminalLink, to identify the
  terminal associated with a streaming interface

Entity ID collisions break accessing controls and make the graph
description in the UVC descriptors ambiguous. However, collisions where
one of the entities is a streaming output terminal and the other entity
is not a streaming terminal are less severe. Streaming output terminals
have no controls, and, as they are the final entity in pipelines, they
are never referenced in descriptors as source entities. They are
referenced by ID only from innput header descriptors, which by
definition only reference streaming terminals.

For these reasons, we can work around the collision by giving streaming
output terminals their own ID namespace. Do so by setting bit
UVC_TERM_OUTPUT (15) in the uvc_entity.id field, which is normally never
set as the ID is a 8-bit value.

This ID change doesn't affect the entity name in the media controller
graph as the name isn't constructed from the ID, so there should not be
any impact on the uAPI.

Although this change handles some ID collisions automagically, keep
printing an error in uvc_alloc_new_entity() when a camera has invalid
descriptors. Hopefully this message will help vendors fix their invalid
descriptors.

This new method of handling ID collisions includes a revert of commit
758dbc756a ("media: uvcvideo: Use heuristic to find stream entity")
that attempted to fix the problem urgently due to regression reports.

Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Lili Orosz <lily@floofy.city>
Co-developed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Link: https://patch.msgid.link/20251113210400.28618-1-laurent.pinchart@ideasonboard.com
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2026-03-04 07:20:02 -05:00
arch parisc: Prevent interrupts during reboot 2026-03-04 07:19:44 -05:00
block block: decouple secure erase size limit from discard size limit 2026-03-04 07:19:38 -05:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: authencesn - reject too-short AAD (assoclen<8) to match ESP/ESN spec 2026-01-30 10:32:12 +01:00
Documentation cgroup/cpuset: Don't fail cpuset.cpus change in v2 2026-03-04 07:19:56 -05:00
drivers media: uvcvideo: Create an ID namespace for streaming output terminals 2026-03-04 07:20:02 -05:00
fs pstore: ram_core: fix incorrect success return when vmap() fails 2026-03-04 07:19:43 -05:00
include PCI: Add Intel Nova Lake audio Device ID 2026-03-04 07:20:00 -05:00
init printk changes for 6.18 2025-10-04 11:13:11 -07:00
io_uring io_uring/timeout: annotate data race in io_flush_timeouts() 2026-03-04 07:19:36 -05:00
ipc ipc: don't audit capability check in ipc_permissions() 2026-02-26 14:59:19 -08:00
kernel cgroup/cpuset: Don't fail cpuset.cpus change in v2 2026-03-04 07:19:56 -05:00
lib objpool: fix the overestimation of object pooling metadata size 2026-02-26 14:59:36 -08:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm mm/slab: fix false lockdep warning in __kfree_rcu_sheaf() 2026-02-26 14:59:14 -08:00
net bpf: net_sched: Use the correct destructor kfunc type 2026-03-04 07:19:40 -05:00
rust rust: cpufreq: always inline functions using build_assert with arguments 2026-03-04 07:19:37 -05:00
samples samples/ftrace: Adjust LoongArch register restore order in direct calls 2026-01-08 10:17:11 +01:00
scripts gendwarfksyms: Fix build on 32-bit hosts 2026-03-04 07:19:40 -05:00
security apparmor: fix aa_label to return state from compount and component match 2026-02-26 14:59:42 -08:00
sound ASoC: soc-acpi-intel-arl-match: change rt722 amp endpoint to aggregated 2026-03-04 07:20:00 -05:00
tools bpftool: Fix dependencies for static build 2026-03-04 07:19:42 -05:00
usr gen_init_cpio: Ignore fsync() returning EINVAL on pipes 2025-10-07 09:53:05 -07:00
virt KVM: Don't clobber irqfd routing type when deassigning irqfd 2026-02-11 13:41:44 +01:00
.clang-format memblock: drop for_each_free_mem_pfn_range_in_zone_from() 2025-09-14 08:49:03 +03:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: remove Alyssa Rosenzweig 2025-09-18 21:17:31 +02:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore .gitignore: ignore compile_commands.json globally 2025-08-12 15:53:55 -07:00
.mailmap 8 hotfixes. 4 are cc:stable, 7 are against mm/. 2025-11-26 12:38:05 -08:00
.pylintrc tools: docs: parse-headers.py: move it from sphinx dir 2025-08-29 15:54:42 -06:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: mark ISDN subsystem as orphan 2025-10-27 17:49:45 -07:00
Kbuild sched: Make migrate_{en,dis}able() inline 2025-09-25 09:57:16 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS soc: fixes for 6.18, part 4 2025-11-28 09:57:31 -08:00
Makefile Linux 6.18.15 2026-02-27 16:05:10 -05:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.