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authorFan Wu <fanwu01@zju.edu.cn>2026-08-20 13:53:06 +0000
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2026-09-01 16:50:04 +0200
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tree861df7c5b878b85741cf319ece81111b4c41c3b1 /Documentation/userspace-api/ioctl/ioctl-decoding.rst
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usb: typec: qcom-pmic-typec: disable cc_debounce_dwork on stopgrafted
cc_debounce_dwork is queued from the set_cc() and start_toggling() callbacks, which run from TCPM's kthread worker. port_stop() returns before tcpm_unregister_port() destroys that worker. Flushing the worker during unregister may therefore run a callback which queues the delayed work after port_stop() has returned. The delayed work can then run after devres has freed pmic_typec_port. Use disable_delayed_work_sync() in port_stop() to cancel a pending instance and prevent the TCPM callbacks from queueing another one. This issue was found by an in-house static analysis tool. Fixes: a4422ff22142 ("usb: typec: qcom: Add Qualcomm PMIC Type-C driver") Cc: stable <stable@kernel.org> # v6.10+ Assisted-by: Codex:gpt-5.6 Signed-off-by: Fan Wu <fanwu01@zju.edu.cn> Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com> Link: https://patch.msgid.link/20260820135307.153773-2-fanwu01@zju.edu.cn Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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+==============================
+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])