rtapi_module_param(3rtapi)

✨ rtapi_module_param — the 3rtapi era ✨

okay bestie, pull up a chair, because this one is the glue that holds your kernel modules together 💅 this page lives in section 3rtapi and it's all about how you declare module parameters like a boss.

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🌸 NAME 🌸

rtapi_module_param — specifying module parameters 🎀

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🦋 SYNTAX 🦋

here's the whole cast, exactly as written, no semicolons, no drama:

RTAPI_MP_INT(var, description)

RTAPI_MP_LONG(var, description)

RTAPI_MP_STRING(var, description)

RTAPI_MP_ARRAY_INT(var, num, description)

RTAPI_MP_ARRAY_LONG(var, num, description)

RTAPI_MP_ARRAY_STRING(var, num, description)

MODULE_LICENSE(license)

MODULE_AUTHOR(author)

MODULE_DESCRIPTION(description)

EXPORT_FUNCTION(function)

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💖 ARGUMENTS 💖

• var — the variable where the parameter should be stored 🫙 that's literally its whole job.
• description — a short description of the parameter or module 📝 keep it cute, keep it short.
• num — the maximum number of values for an array parameter 🔢 that's the cap, bestie.
• license — the license of the module, for instance "GPL" ⚖️
• author — the author of the module 👑 you. it's you.
• function — the pointer to the function to be exported 📤

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🌈 DESCRIPTION 🌈

so these macros are portable ways to declare kernel module parameters ✨ that's the whole vibe.

the rules, and they are not optional:

• they must be used in the global scope 🌍
• they are not followed by a terminating semicolon 🚫;
• they must be used after the associated variable or function has been defined ⏳ order matters, no cap.

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🎀 NOTES 🎀

EXPORT_FUNCTION makes a symbol available for use by a subsequently loaded component 🔗

⚠️ it is unrelated to HAL functions, which are described in hal_export_funct(3hal). do not mix these up, i am begging 🙈

💜 Interpretation of license strings 💜

MODULE_LICENSE follows the kernel's definition of license strings. notably, "GPL" indicates "GNU General Public License v2 or later" (emphasis ours). periodt.

• "GPL" — GNU General Public License v2 or later
• "GPL v2" — GNU General Public License v2
• "GPL and additional rights" — GNU General Public License v2 rights and more
• "Dual BSD/GPL" — GNU General Public License v2 or BSD license choice
• "Dual MIT/GPL" — GNU General Public License v2 or MIT license choice
• "Dual MPL/GPL" — GNU General Public License v2 or Mozilla license choice
• "Proprietary" — Non-free products

and ngl, it is still good practice to include a license block which indicates the author, copyright date, and disclaimer of warranty as recommended by the GNU GPL 🫶 do it for the culture.

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⏰ REALTIME CONSIDERATIONS ⏰

Not available in userspace code. 🚫 userland girlies, this one is not for you, sorry bestie 💀

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and that's the whole page, babes 💅 written up by the LinuxCNC Documentation crew, dated 2006-10-12, and it belongs to the rtapi_module_param(3rtapi) era — iconic, historic, and honestly? still ate. mwah 🎀✨