From f4cdf7ca9a1fdcca413157df19753f388a5a224e Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 19 Aug 2026 10:09:22 -0700 Subject: Merge tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media Pull media updates from Mauro Carvalho Chehab: - v4l2-core: added ISP statistics support and per-block validation - v4l2-core: Allow unknown HDR10 white point and luminance - New camera sensors: Sony IMX678 and IMX471m, Himax HM1092 IR sensor - New codec: Milos: VPU v2.0 codec support - isp driver: gained support for Dreamchip RPPX1 ISP framework - vsp1 driver: gained support for RZ/T2H and RZ/N2H - Novalake driver: gained CVS support for new NVL hardware - dvb-core: fix feed leak on failed DMX_ADD_PID - several driver fixes, cleanups and minor improvements * tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-media: (308 commits) media: ipu-bridge: check all DMI entries when overriding sensor rotation media: v4l2-async: avoid deleting unlinked ASC entry on link error media: rzg2l-cru: Align bytesperline to hardware DMA stride requirement media: intel/ipu6: fix async notifier cleanup leak on parse error media: staging/ipu7: fix async notifier UAF on probe error path media: amd: isp4: fix self-deadlock in isp4sd_pwron_and_init() error path media: amd: isp4: release partial allocations in isp4if_alloc_fw_gpumem() media: rcar-isp: Fix VSPX reference leaks media: rcar-isp: Release ISPCORE resources media: i2c: imx415: Release runtime PM reference on VBLANK error media: i2c: imx415: Return test pattern write errors media: renesas: vsp1: Declare index variables in for loop statement media: renesas: vsp1: Make reset control optional to support platforms without a reset line media: dt-bindings: media: renesas,vsp1: Document RZ/T2H and RZ/N2H SoCs media: dt-bindings: media: renesas,fcp: Document RZ/T2H and RZ/N2H SoCs media: nxp: imx8-isi: Add additional 32-bit RGB format support media: nxp: imx8-isi: Add 16-bit raw Bayer format support media: nxp: imx8-isi: Implement per-stream reference counting for multiplexed streams media: nxp: imx8-isi: Use BIT_ULL() for 64-bit stream masks media: nxp: imx8-isi: Correct color map between V4L2 and ISI ... --- Documentation/trace/remotes.rst | 66 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 66 insertions(+) create mode 100644 Documentation/trace/remotes.rst (limited to 'Documentation/trace/remotes.rst') diff --git a/Documentation/trace/remotes.rst b/Documentation/trace/remotes.rst new file mode 100644 index 000000000..1f9d764f6 --- /dev/null +++ b/Documentation/trace/remotes.rst @@ -0,0 +1,66 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============== +Tracing Remotes +=============== + +:Author: Vincent Donnefort + +Overview +======== +Firmware and hypervisors are black boxes to the kernel. Having a way to see what +they are doing can be useful to debug both. This is where remote tracing buffers +come in. A remote tracing buffer is a ring buffer executed by the firmware or +hypervisor into memory that is memory mapped to the host kernel. This is similar +to how user space memory maps the kernel ring buffer but in this case the kernel +is acting like user space and the firmware or hypervisor is the "kernel" side. +With a trace remote ring buffer, the firmware and hypervisor can record events +for which the host kernel can see and expose to user space. + +Register a remote +================= +A remote must provide a set of callbacks `struct trace_remote_callbacks` whom +description can be found below. Those callbacks allows Tracefs to enable and +disable tracing and events, to load and unload a tracing buffer (a set of +ring-buffers) and to swap a reader page with the head page, which enables +consuming reading. + +.. kernel-doc:: include/linux/trace_remote.h + +Once registered, an instance will appear for this remote in the Tracefs +directory **remotes/**. Buffers can then be read using the usual Tracefs files +**trace_pipe** and **trace**. + +Declare a remote event +====================== +Macros are provided to ease the declaration of remote events, in a similar +fashion to in-kernel events. A declaration must provide an ID, a description of +the event arguments and how to print the event: + +.. code-block:: c + + REMOTE_EVENT(foo, EVENT_FOO_ID, + RE_STRUCT( + re_field(u64, bar) + ), + RE_PRINTK("bar=%lld", __entry->bar) + ); + +Then those events must be declared in a C file with the following: + +.. code-block:: c + + #define REMOTE_EVENT_INCLUDE_FILE foo_events.h + #include + +This will provide a `struct remote_event remote_event_foo` that can be given to +`trace_remote_register`. + +Registered events appear in the remote directory under **events/**. + +Simple ring-buffer +================== +A simple implementation for a ring-buffer writer can be found in +kernel/trace/simple_ring_buffer.c. + +.. kernel-doc:: include/linux/simple_ring_buffer.h -- cgit v1.3.1