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https://github.com/cirosantilli/linux-kernel-module-cheat.git
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ca231b82f6
Rationale: we already had a non buildroot build system, maintaining both will be hard, and having short paths is more awesome.
43 lines
1.5 KiB
C
43 lines
1.5 KiB
C
#ifndef IOCTL_H
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#define IOCTL_H
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#include <linux/ioctl.h>
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/* Structs are the way to pass multiple arguments. */
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typedef struct {
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int i;
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int j;
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} lkmc_ioctl_struct;
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/* TODO some random number I can't understand how to choose. */
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#define LKMC_IOCTL_MAGIC 0x33
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/* I think those number do not *need* to be unique across, that is just to help debugging:
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* https://stackoverflow.com/questions/22496123/what-is-the-meaning-of-this-macro-iormy-macig-0-int
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*
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* However, the ioctl syscall highjacks several low values at do_vfs_ioctl, e.g.
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* This "forces" use to use the _IOx macros...
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* https://stackoverflow.com/questions/10071296/ioctl-is-not-called-if-cmd-2
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*
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* Some of those magic low values are used for fnctl, which can also be used on regular files:
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* e.g. FIOCLEX for close-on-exec:
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* https://stackoverflow.com/questions/6125068/what-does-the-fd-cloexec-fcntl-flag-do
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*
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* TODO are the W or R of _IOx and type functional, or only to help with uniqueness?
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*
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* Documentation/ioctl/ioctl-number.txt documents:
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*
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* ....
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* _IO an ioctl with no parameters
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* _IOW an ioctl with write parameters (copy_from_user)
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* _IOR an ioctl with read parameters (copy_to_user)
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* _IOWR an ioctl with both write and read parameters.
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* ....
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*/
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/* Take an int, increment it. */
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#define LKMC_IOCTL_INC _IOWR(LKMC_IOCTL_MAGIC, 0, int)
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/* Take a struct with two ints, increment the first, and decrement the second. */
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#define LKMC_IOCTL_INC_DEC _IOWR(LKMC_IOCTL_MAGIC, 1, lkmc_ioctl_struct)
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#endif
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