From dd05add7b2b6004c5fa3a1f276f56d8668f86b65 Mon Sep 17 00:00:00 2001 From: Paulo Alcantara Date: Sat, 26 Sep 2026 19:20:30 -0300 Subject: netfs: zero the tail of a short DIO/unbuffered read The buffered read collector zero-fills the tail of a short read that stops below the inode's i_size (netfs_clear_unread()), so a read that races an extending write still returns the expected number of bytes. The non-buffered collector path does no such thing: it just records how much was transferred. Add the same zero-fill for the non-buffered case, gated on NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short result from it is known to be safe to treat as a hole, as opposed to NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of the file and should be reported short as-is. Only CLEAR_TAIL should zero-fill here; a real EOF must stay a real short read. No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest, so this is inert on its own -- a following change teaches cifs to set it in the one case that needs it. Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item") Reviewed-by: David Howells Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Christian Brauner Cc: Matthew Wilcox Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org --- .../admin-guide/media/remote-controller.rst | 76 ++++++++++++++++++++++ 1 file changed, 76 insertions(+) create mode 100644 Documentation/admin-guide/media/remote-controller.rst (limited to 'Documentation/admin-guide/media/remote-controller.rst') diff --git a/Documentation/admin-guide/media/remote-controller.rst b/Documentation/admin-guide/media/remote-controller.rst new file mode 100644 index 000000000..188944b00 --- /dev/null +++ b/Documentation/admin-guide/media/remote-controller.rst @@ -0,0 +1,76 @@ +.. SPDX-License-Identifier: GPL-2.0 + +====================================================== +Infrared remote control support in video4linux drivers +====================================================== + +Authors: Gerd Hoffmann, Mauro Carvalho Chehab + +Basics +====== + +Most analog and digital TV boards support remote controllers. Several of +them have a microprocessor that receives the IR carriers, convert into +pulse/space sequences and then to scan codes, returning such codes to +userspace ("scancode mode"). Other boards return just the pulse/space +sequences ("raw mode"). + +The support for remote controller in scancode mode is provided by the +standard Linux input layer. The support for raw mode is provided via LIRC. + +In order to check the support and test it, it is suggested to download +the `v4l-utils `_. It provides +two tools to handle remote controllers: + +- ir-keytable: provides a way to query the remote controller, list the + protocols it supports, enable in-kernel support for IR decoder or + switch the protocol and to test the reception of scan codes; + +- ir-ctl: provide tools to handle remote controllers that support raw mode + via LIRC interface. + +Usually, the remote controller module is auto-loaded when the TV card is +detected. However, for a few devices, you need to manually load the +ir-kbd-i2c module. + +How it works +============ + +The modules register the remote as keyboard within the linux input +layer, i.e. you'll see the keys of the remote as normal key strokes +(if CONFIG_INPUT_KEYBOARD is enabled). + +Using the event devices (CONFIG_INPUT_EVDEV) it is possible for +applications to access the remote via /dev/input/event devices. +The udev/systemd will automatically create the devices. If you install +the `v4l-utils `_, it may also +automatically load a different keytable than the default one. Please see +`v4l-utils `_ ir-keytable.1 +man page for details. + +The ir-keytable tool is nice for trouble shooting, i.e. to check +whenever the input device is really present, which of the devices it +is, check whenever pressing keys on the remote actually generates +events and the like. You can also use any other input utility that changes +the keymaps, like the input kbd utility. + + +Using with lircd +---------------- + +The latest versions of the lircd daemon supports reading events from the +linux input layer (via event device). It also supports receiving IR codes +in lirc mode. + + +Using without lircd +------------------- + +Xorg recognizes several IR keycodes that have its numerical value lower +than 247. With the advent of Wayland, the input driver got updated too, +and should now accept all keycodes. Yet, you may want to just reassign +the keycodes to something that your favorite media application likes. + +This can be done by setting +`v4l-utils `_ to load your own +keytable in runtime. Please read ir-keytable.1 man page for details. -- cgit v1.3.1