summaryrefslogtreecommitdiffstats
path: root/Documentation/driver-api/soundwire/locking.rst
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2026-08-19 10:09:22 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2026-08-19 10:09:22 -0700
commitf4cdf7ca9a1fdcca413157df19753f388a5a224e (patch)
tree60a31895b2446cd7fa27514e8c2843534a0de0da /Documentation/driver-api/soundwire/locking.rst
downloadlinux-stable-f4cdf7ca9a1fdcca413157df19753f388a5a224e.tar.gz
linux-stable-f4cdf7ca9a1fdcca413157df19753f388a5a224e.zip
Merge tag 'media/v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-mediagrafted
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 ...
Diffstat (limited to 'Documentation/driver-api/soundwire/locking.rst')
-rw-r--r--Documentation/driver-api/soundwire/locking.rst108
1 files changed, 108 insertions, 0 deletions
diff --git a/Documentation/driver-api/soundwire/locking.rst b/Documentation/driver-api/soundwire/locking.rst
new file mode 100644
index 000000000..3a7ffb3d8
--- /dev/null
+++ b/Documentation/driver-api/soundwire/locking.rst
@@ -0,0 +1,108 @@
+=================
+SoundWire Locking
+=================
+
+This document explains locking mechanism of the SoundWire Bus. Bus uses
+following locks in order to avoid race conditions in Bus operations on
+shared resources.
+
+ - Bus lock
+
+ - Message lock
+
+Bus lock
+========
+
+SoundWire Bus lock is a mutex and is part of Bus data structure
+(sdw_bus) which is used for every Bus instance. This lock is used to
+serialize each of the following operations(s) within SoundWire Bus instance.
+
+ - Addition and removal of Slave(s), changing Slave status.
+
+ - Prepare, Enable, Disable and De-prepare stream operations.
+
+ - Access of Stream data structure.
+
+Message lock
+============
+
+SoundWire message transfer lock. This mutex is part of
+Bus data structure (sdw_bus). This lock is used to serialize the message
+transfers (read/write) within a SoundWire Bus instance.
+
+Below examples show how locks are acquired.
+
+Example 1
+---------
+
+Message transfer.
+
+ 1. For every message transfer
+
+ a. Acquire Message lock.
+
+ b. Transfer message (Read/Write) to Slave1 or broadcast message on
+ Bus in case of bank switch.
+
+ c. Release Message lock
+
+ ::
+
+ +----------+ +---------+
+ | | | |
+ | Bus | | Master |
+ | | | Driver |
+ | | | |
+ +----+-----+ +----+----+
+ | |
+ | bus->ops->xfer_msg() |
+ <-------------------------------+ a. Acquire Message lock
+ | | b. Transfer message
+ | |
+ +-------------------------------> c. Release Message lock
+ | return success/error | d. Return success/error
+ | |
+ + +
+
+Example 2
+---------
+
+Prepare operation.
+
+ 1. Acquire lock for Bus instance associated with Master 1.
+
+ 2. For every message transfer in Prepare operation
+
+ a. Acquire Message lock.
+
+ b. Transfer message (Read/Write) to Slave1 or broadcast message on
+ Bus in case of bank switch.
+
+ c. Release Message lock.
+
+ 3. Release lock for Bus instance associated with Master 1 ::
+
+ +----------+ +---------+
+ | | | |
+ | Bus | | Master |
+ | | | Driver |
+ | | | |
+ +----+-----+ +----+----+
+ | |
+ | sdw_prepare_stream() |
+ <-------------------------------+ 1. Acquire bus lock
+ | | 2. Perform stream prepare
+ | |
+ | |
+ | bus->ops->xfer_msg() |
+ <-------------------------------+ a. Acquire Message lock
+ | | b. Transfer message
+ | |
+ +-------------------------------> c. Release Message lock
+ | return success/error | d. Return success/error
+ | |
+ | |
+ | return success/error | 3. Release bus lock
+ +-------------------------------> 4. Return success/error
+ | |
+ + +