From 034dd340b08be1f2f0477ad16131d609f9dbd53c Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 30 Aug 2026 09:22:00 -0700 Subject: Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace Pull tracing fixes from Steven Rostedt: - Fix error output of boot instance creation failure Currently if a boot instance creation fails, instead of printing out the name of the instance that failed, it prints "(null)". That is because it prints "cur_str" that had already been processed by strsep(). Print the saved name instead. While at it, print the error code of the failure. - Fix use-after-free for same named historgrams Histograms can be named so that they can be used in multiple events. But if the named histogram has a variable attached, the second event that uses the named histogram which duplicates it and needs to free the original after duplication leaves the old variable in place and still visible. If another histogram uses than variable, it will use the stale one which will try to reference the freed duplicate histogram and crash the kernel. Free the duplicate variables along with the duplicated histogram data. - Check return value of kthread_run() in event self test The events self tests uses a kthread for testing but does not check if it succeeded in creating a kthread. If the kthread creation were to fail, the code will still try to call kthread_stop() on the error returned. - Fix race between reading trace_pipe and updating subbuffer size If a user is reading the trace_pipe file at the same time they update the ring buffer sub-buffer size, can cause the trace_pipe read to read stale data. Add trace_access_lock() around updating the ring buffer sub-buffer size. - Fix eventfs_inode on failure path in creation of the events directory In the creation of the "events" directory, if after allocating the eventfs_inode a failure is detected, it calls cleanup_ei() which calls free_ei(). The free_ei() will test if eventfs_inode being freed has no children. It is a bug if it does. But on the failure case of the creation of the "events" directory, the children lists have not yet been initialized and the free will trigger a warning because list_empty() on an uninitialized list returns false. Move the initialization into init_ei() where it makes more sense and makes sure that a created eventfs_inode has its lists initialized upon creation. - Check return value of kthread_run() in ftrace direct sample code The sample code that shows how to use the ftrace direct calls does not test the return of kthread_run() to see if it succeeds. Return a failure if the kthread_run() doesn't succeed. - Clear user events state on fork in case of alloc failure On fork, the child gets a pointer to the parent's user events state. It makes a copy of it then updates the child's pointer to it. But if the allocation fails, the duplication function leaves the child with a pointer to its parent's descriptor. When the child cleans up its data, it will free the parent's descriptor while the parent is still using it. In the duplication function, set the child's user_event_mm to NULL before testing if the allocation succeeded, and when it exits it will not free the parent's descriptor. - Fix retry exhaustion in simple ring buffer reader swap simple_ring_buffer_swap_reader_page() starts with retry set to 8 and post-decrements it only after a failed link replacement. On the final attempt, a successful replacement leaves retry at zero, while a failed replacement leaves it at -1. But the check for success expects the retry value to be non-zero and exits with an error on zero. This is the opposite result. Fix it. - Fail nicely when the remote swap_reader_page() returns an error Currently, if the swap_reader_page() of a remote buffer fails, it triggers a WARN_ON_ONCE() and continues normally. Instead, have it exit with an error and a pr_warn() print instead of a full WARNING. * tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ring-buffer: Stop remote reader update when page swap fails tracing: Fix retry exhaustion in simple ring buffer reader swap tracing/user_events: Clear copied tracing state before fork duplication samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify eventfs: Initialize ei->children and ei->list in init_ei() tracing: Fix use-after-free in trace_pipe read on sub-buffer order change tracing: Fix crash passing ERR_PTR to kthread_stop() tracing: Fix use-after-free with same-name named triggers tracing: Fix logged instance name on creation failure --- Documentation/admin-guide/media/vimc.rst | 110 +++++++++++++++++++++++++++++++ 1 file changed, 110 insertions(+) create mode 100644 Documentation/admin-guide/media/vimc.rst (limited to 'Documentation/admin-guide/media/vimc.rst') diff --git a/Documentation/admin-guide/media/vimc.rst b/Documentation/admin-guide/media/vimc.rst new file mode 100644 index 000000000..29d843a8d --- /dev/null +++ b/Documentation/admin-guide/media/vimc.rst @@ -0,0 +1,110 @@ +.. SPDX-License-Identifier: GPL-2.0 + +The Virtual Media Controller Driver (vimc) +========================================== + +The vimc driver emulates complex video hardware using the V4L2 API and the Media +API. It has a capture device and three subdevices: sensor, debayer and scaler. + +Topology +-------- + +The topology is hardcoded, although you could modify it in vimc-core and +recompile the driver to achieve your own topology. This is the default topology: + +.. _vimc_topology_graph: + +.. kernel-figure:: vimc.dot + :alt: Diagram of the default media pipeline topology + :align: center + + Media pipeline graph on vimc + +Configuring the topology +~~~~~~~~~~~~~~~~~~~~~~~~ + +Each subdevice will come with its default configuration (pixelformat, height, +width, ...). One needs to configure the topology in order to match the +configuration on each linked subdevice to stream frames through the pipeline. +If the configuration doesn't match, the stream will fail. The ``v4l-utils`` +package is a bundle of user-space applications, that comes with ``media-ctl`` and +``v4l2-ctl`` that can be used to configure the vimc configuration. This sequence +of commands fits for the default topology: + +.. code-block:: bash + + media-ctl -d platform:vimc -V '"Sensor A":0[fmt:SBGGR8_1X8/640x480]' + media-ctl -d platform:vimc -V '"Debayer A":0[fmt:SBGGR8_1X8/640x480]' + media-ctl -d platform:vimc -V '"Scaler":0[fmt:RGB888_1X24/640x480]' + media-ctl -d platform:vimc -V '"Scaler":0[crop:(100,50)/400x150]' + media-ctl -d platform:vimc -V '"Scaler":1[fmt:RGB888_1X24/300x700]' + v4l2-ctl -z platform:vimc -d "RGB/YUV Capture" -v width=300,height=700 + v4l2-ctl -z platform:vimc -d "Raw Capture 0" -v pixelformat=BA81 + +Subdevices +---------- + +Subdevices define the behavior of an entity in the topology. Depending on the +subdevice, the entity can have multiple pads of type source or sink. + +vimc-sensor: + Generates images in several formats using video test pattern generator. + Exposes: + + * 1 Pad source + +vimc-lens: + Ancillary lens for a sensor. Supports auto focus control. Linked to + a vimc-sensor using an ancillary link. The lens supports FOCUS_ABSOLUTE + control. + +.. code-block:: bash + + media-ctl -p + ... + - entity 28: Lens A (0 pad, 0 link) + type V4L2 subdev subtype Lens flags 0 + device node name /dev/v4l-subdev6 + - entity 29: Lens B (0 pad, 0 link) + type V4L2 subdev subtype Lens flags 0 + device node name /dev/v4l-subdev7 + v4l2-ctl -d /dev/v4l-subdev7 -C focus_absolute + focus_absolute: 0 + + +vimc-debayer: + Transforms images in bayer format into a non-bayer format. + Exposes: + + * 1 Pad sink + * 1 Pad source + +vimc-scaler: + Re-size the image to meet the source pad resolution. E.g.: if the sync + pad is configured to 360x480 and the source to 1280x720, the image will + be stretched to fit the source resolution. Works for any resolution + within the vimc limitations (even shrinking the image if necessary). + Exposes: + + * 1 Pad sink + * 1 Pad source + +vimc-capture: + Exposes node /dev/videoX to allow userspace to capture the stream. + Exposes: + + * 1 Pad sink + * 1 Pad source + +Module options +-------------- + +Vimc has a module parameter to configure the driver. + +* ``allocator=`` + + memory allocator selection, default is 0. It specifies the way buffers + will be allocated. + + - 0: vmalloc + - 1: dma-contig -- cgit v1.3.1