From 9f0346dcbea363787186c94ef94dd01aaa215afa Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sat, 5 Sep 2026 11:59:05 -0700 Subject: Merge tag 'driver-core-7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core Pull driver core fixes from Danilo Krummrich: - Fix kernfs listxattr() not returning security xattr names (e.g. SELinux labels) when the kernfs node has no allocated kernfs_iattrs - Fix silent truncation of IRQ vector indices in the Rust PCI abstractions - Don't select OF from DRIVER_PE_KUNIT_TEST; skip the test when OF is disabled instead of silently enabling extra kernel functionality - Russ Weight is retiring from kernel development; update the Firmware Loader sysfs contact to the driver-core mailing list, add a CREDITS entry for Firmware Upload, and update MAINTAINERS accordingly * tag 'driver-core-7.3-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core: MAINTAINERS: Remove Russ Weight from Firmware Loader CREDITS: Add CREDITS entry for Firmware Upload firmware_loader: Change contact for sysfs nodes rust: pci: reject IRQ vector indices that do not fit in u32 kernfs: preserve security xattrs without allocating iattrs drivers: base: test: DRIVER_PE_KUNIT_TEST should not select OF --- .../userspace-api/ioctl/ioctl-decoding.rst | 31 ++++++++++++++++++++++ 1 file changed, 31 insertions(+) create mode 100644 Documentation/userspace-api/ioctl/ioctl-decoding.rst (limited to 'Documentation/userspace-api/ioctl/ioctl-decoding.rst') diff --git a/Documentation/userspace-api/ioctl/ioctl-decoding.rst b/Documentation/userspace-api/ioctl/ioctl-decoding.rst new file mode 100644 index 000000000..380d6bb3e --- /dev/null +++ b/Documentation/userspace-api/ioctl/ioctl-decoding.rst @@ -0,0 +1,31 @@ +============================== +Decoding an IOCTL Magic Number +============================== + +To decode a hex IOCTL code: + +Most architectures use this generic format, but check +include/ARCH/ioctl.h for specifics, e.g. powerpc +uses 3 bits to encode read/write and 13 bits for size. + + ====== ================================== + bits meaning + ====== ================================== + 31-30 00 - no parameters: uses _IO macro + 10 - read: _IOR + 01 - write: _IOW + 11 - read/write: _IOWR + + 29-16 size of arguments + + 15-8 ascii character supposedly + unique to each driver + + 7-0 function # + ====== ================================== + + +So for example 0x82187201 is a read with arg length of 0x218, +character 'r' function 1. Grepping the source reveals this is:: + + #define VFAT_IOCTL_READDIR_BOTH _IOR('r', 1, struct dirent [2]) -- cgit v1.3.1