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/filesystems/dnotify.rst | 75 +++++++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+) create mode 100644 Documentation/filesystems/dnotify.rst (limited to 'Documentation/filesystems/dnotify.rst') diff --git a/Documentation/filesystems/dnotify.rst b/Documentation/filesystems/dnotify.rst new file mode 100644 index 000000000..a28a1f9ef --- /dev/null +++ b/Documentation/filesystems/dnotify.rst @@ -0,0 +1,75 @@ +.. SPDX-License-Identifier: GPL-2.0 + +============================ +Linux Directory Notification +============================ + + Stephen Rothwell + +The intention of directory notification is to allow user applications +to be notified when a directory, or any of the files in it, are changed. +The basic mechanism involves the application registering for notification +on a directory using a fcntl(2) call and the notifications themselves +being delivered using signals. + +The application decides which "events" it wants to be notified about. +The currently defined events are: + + ========= ===================================================== + DN_ACCESS A file in the directory was accessed (read) + DN_MODIFY A file in the directory was modified (write,truncate) + DN_CREATE A file was created in the directory + DN_DELETE A file was unlinked from directory + DN_RENAME A file in the directory was renamed + DN_ATTRIB A file in the directory had its attributes + changed (chmod,chown) + ========= ===================================================== + +Usually, the application must reregister after each notification, but +if DN_MULTISHOT is or'ed with the event mask, then the registration will +remain until explicitly removed (by registering for no events). + +By default, SIGIO will be delivered to the process and no other useful +information. However, if the F_SETSIG fcntl(2) call is used to let the +kernel know which signal to deliver, a siginfo structure will be passed to +the signal handler and the si_fd member of that structure will contain the +file descriptor associated with the directory in which the event occurred. + +Preferably the application will choose one of the real time signals +(SIGRTMIN + ) so that the notifications may be queued. This is +especially important if DN_MULTISHOT is specified. Note that SIGRTMIN +is often blocked, so it is better to use (at least) SIGRTMIN + 1. + +Implementation expectations (features and bugs :-)) +--------------------------------------------------- + +The notification should work for any local access to files even if the +actual file system is on a remote server. This implies that remote +access to files served by local user mode servers should be notified. +Also, remote accesses to files served by a local kernel NFS server should +be notified. + +In order to make the impact on the file system code as small as possible, +the problem of hard links to files has been ignored. So if a file (x) +exists in two directories (a and b) then a change to the file using the +name "a/x" should be notified to a program expecting notifications on +directory "a", but will not be notified to one expecting notifications on +directory "b". + +Also, files that are unlinked, will still cause notifications in the +last directory that they were linked to. + +Configuration +------------- + +Dnotify is controlled via the CONFIG_DNOTIFY configuration option. When +disabled, fcntl(fd, F_NOTIFY, ...) will return -EINVAL. + +Example +------- +See tools/testing/selftests/filesystems/dnotify_test.c for an example. + +NOTE +---- +Beginning with Linux 2.6.13, dnotify has been replaced by inotify. +See Documentation/filesystems/inotify.rst for more information on it. -- cgit v1.3.1