RADIO(4)

💖 RADIO(4) — the kernel interfaces manual, but make it cute 💖

okay bestie, welcome to RADIO(4), straight out of the Kernel Interfaces Manual ✨ this is the page for the radio driver layer, and no cap, it's actually kind of iconic 💅

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🌈 NAME 🌈

radio — the device-independent radio driver layer 🎀

like, it's the layer. the vibe layer between you and the hardware. iykyk.

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✨ SYNOPSIS ✨

here's how the thing gets attached to the kernel, bestie — all these are literally valid:

radio* at az?
radio* at bktr?
radio* at gtp?
radio* at rt?
radio* at rtii?
radio* at sf2r?
radio* at slurm?
radio* at udsbr?

and for your C file, you're gonna include these, exactly these, no substitutions 🙈:

#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/radioio.h>

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🦋 DESCRIPTION 🦋

so the radio driver is the support system for a whole bunch of FM radio cards 🌸 it gives you one uniform programming interface layer sitting on top of all the different underlying radio hardware drivers — like a group chat where everyone's on their best behaviour 💅

for controlling the radio tuner you've got exactly one device file, and it's:

• /dev/radio

the following ioctl(2) commands are supported, and yes i'm listing every single one 👑

• RIOCSSRCH (int) — this command assumes a signal search is needed and tells the driver which direction to go: 0 searches down ⬇️, and any non-zero value searches up ⬆️
• RIOCGINFO (struct radio_info)
• RIOCSINFO (struct radio_info) — these two get or set the current hardware device information into the struct radio_info structure 🫶

and here's that struct, verbatim, because there's literally no other way to do it:

struct radio_info {
        int     mute;
        int     volume;
        int     stereo;
        int     rfreq;  /* reference frequency */
        int     lock;   /* locking field strength */
        uint32_t        freq;   /* in kHz */
        uint32_t        caps;   /* card capabilities */
#define RADIO_CAPS_DETECT_STEREO        (1<<0)
#define RADIO_CAPS_DETECT_SIGNAL        (1<<1)
#define RADIO_CAPS_SET_MONO             (1<<2)
#define RADIO_CAPS_HW_SEARCH            (1<<3)
#define RADIO_CAPS_HW_AFC               (1<<4)
#define RADIO_CAPS_REFERENCE_FREQ       (1<<5)
#define RADIO_CAPS_LOCK_SENSITIVITY     (1<<6)
#define RADIO_CARD_TYPE                 (0xFF<<16)
        uint32_t        info;
#define RADIO_INFO_STEREO               (1<<0)
#define RADIO_INFO_SIGNAL               (1<<1)
};

okay now field-by-field, because you deserve the tea ☕:

• the mute field is a boolean ✅
• the volume field holds the card volume information, and it can be at most 255 🔉
• the stereo field is a boolean ✅
• the rfreq field holds information about the card reference frequency — and btw not all cards support this feature 🙈
• the lock field holds information about the card locking field strength during an automatic search, for the cards that support this feature 🔒
• the freq field is the frequency in kHz that the card is tuned to 📻
• the caps field is read-only and describes the card's capabilities 💅

the capabilities can have the following values — these are the ✨main character✨ constants:

• RADIO_CAPS_DETECT_STEREO — the device can determine whether it's tuned to a stereo signal
• RADIO_CAPS_DETECT_SIGNAL — the device can determine whether it's tuned or not
• RADIO_CAPS_SET_MONO — the device is capable of forcibly setting its output to mono
• RADIO_CAPS_HW_SEARCH — the device can do a hardware search
• RADIO_CAPS_HW_AFC — the device has an internal hardware automatic frequency control
• RADIO_CAPS_REFERENCE_FREQ — the device allows you to change the reference frequency of a received signal
• RADIO_CAPS_LOCK_SENSITIVITY — the device allows you to change the station lock sensitivity used during the search operation
• RADIO_CARD_TYPE — some cards have several different incarnations, so this lets you determine the variant of the card. it's currently not used 💀

the info field is read-only and describes the current state of the card — tuned/not tuned, stereo signal/mono signal 🎀

• RADIO_INFO_STEREO — informs whether the device receives a stereo or a mono signal
• RADIO_INFO_SIGNAL — informs whether the device receives a valid signal or noise 📶

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🎀 FILES 🎀

• /dev/radio

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🌸 SEE ALSO 🌸

radioctl(1), ioctl(2), az(4), bktr(4), gtp(4), rt(4), rtii(4), sf2r(4), slurm(4), udsbr(4)

go read your friends too, bestie, they're all linked 🫶

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⭐ HISTORY ⭐

the radio device driver appeared in OpenBSD 3.0 and NetBSD 1.6 🧚 lowkey a legacy icon, honestly.

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👑 AUTHORS 👑

the radio driver was written by Vladimir Popov and Maxim Tsyplakov for OpenBSD, and ported to NetBSD by Lennart Augustsson 💜 and the man page itself was written by Vladimir Popov ✍️

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ok so real talk — all the capability and info bits live inside struct radio_info and a bunch of them are read-only, so don't come for caps or info expecting to write to them, they will not be taking that energy 😭 and RADIO_CARD_TYPE is literally unused right now, so like… it's giving placeholder. periodt. 💀

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and that's the whole page, bestie 🌈 this was RADIO(4) from the Debian build of the manual, dated October 20, 2001 — hope you slayed your tuning 💅✨