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/admin-guide/binderfs.rst | 87 ++++++++++++++++++++++++++++++++++ 1 file changed, 87 insertions(+) create mode 100644 Documentation/admin-guide/binderfs.rst (limited to 'Documentation/admin-guide/binderfs.rst') diff --git a/Documentation/admin-guide/binderfs.rst b/Documentation/admin-guide/binderfs.rst new file mode 100644 index 000000000..41a4db00d --- /dev/null +++ b/Documentation/admin-guide/binderfs.rst @@ -0,0 +1,87 @@ +.. SPDX-License-Identifier: GPL-2.0 + +The Android binderfs Filesystem +=============================== + +Android binderfs is a filesystem for the Android binder IPC mechanism. It +allows to dynamically add and remove binder devices at runtime. Binder devices +located in a new binderfs instance are independent of binder devices located in +other binderfs instances. Mounting a new binderfs instance makes it possible +to get a set of private binder devices. + +Mounting binderfs +----------------- + +Android binderfs can be mounted with:: + + mkdir /dev/binderfs + mount -t binder binder /dev/binderfs + +at which point a new instance of binderfs will show up at ``/dev/binderfs``. +In a fresh instance of binderfs no binder devices will be present. There will +only be a ``binder-control`` device which serves as the request handler for +binderfs. Mounting another binderfs instance at a different location will +create a new and separate instance from all other binderfs mounts. This is +identical to the behavior of e.g. ``devpts`` and ``tmpfs``. The Android +binderfs filesystem can be mounted in user namespaces. + +Options +------- +max + binderfs instances can be mounted with a limit on the number of binder + devices that can be allocated. The ``max=`` mount option serves as + a per-instance limit. If ``max=`` is set then only ```` number + of binder devices can be allocated in this binderfs instance. + +stats + Using ``stats=global`` enables global binder statistics. + ``stats=global`` is only available for a binderfs instance mounted in the + initial user namespace. An attempt to use the option to mount a binderfs + instance in another user namespace will return a permission error. + +Allocating binder Devices +------------------------- + +.. _ioctl: http://man7.org/linux/man-pages/man2/ioctl.2.html + +To allocate a new binder device in a binderfs instance a request needs to be +sent through the ``binder-control`` device node. A request is sent in the form +of an `ioctl() `_. + +What a program needs to do is to open the ``binder-control`` device node and +send a ``BINDER_CTL_ADD`` request to the kernel. Users of binderfs need to +tell the kernel which name the new binder device should get. By default a name +can only contain up to ``BINDERFS_MAX_NAME`` chars including the terminating +zero byte. + +Once the request is made via an `ioctl() `_ passing a ``struct +binder_device`` with the name to the kernel it will allocate a new binder +device and return the major and minor number of the new device in the struct +(This is necessary because binderfs allocates a major device number +dynamically.). After the `ioctl() `_ returns there will be a new +binder device located under /dev/binderfs with the chosen name. + +Deleting binder Devices +----------------------- + +.. _unlink: http://man7.org/linux/man-pages/man2/unlink.2.html +.. _rm: http://man7.org/linux/man-pages/man1/rm.1.html + +Binderfs binder devices can be deleted via `unlink() `_. This means +that the `rm() `_ tool can be used to delete them. Note that the +``binder-control`` device cannot be deleted since this would make the binderfs +instance unusable. The ``binder-control`` device will be deleted when the +binderfs instance is unmounted and all references to it have been dropped. + +Binder features +--------------- + +Assuming an instance of binderfs has been mounted at ``/dev/binderfs``, the +features supported by the binder driver can be located under +``/dev/binderfs/features/``. The presence of individual files can be tested +to determine whether a particular feature is supported by the driver. + +Example:: + + cat /dev/binderfs/features/oneway_spam_detection + 1 -- cgit v1.3.1