STRUCT MAX3191X_CHIP(9)

💅 struct max3191x_chip(9) — the max3191x daisy-chain, explained by your favorite kernel bestie

okay so this is from the Kernel API Manual, and it's literally the struct that makes a whole daisy-chain of max3191x chips behave like one big happy GPIO family. let's get into it 🎀

✨ NAME ✨

struct max3191x_chip — max3191x daisy-chain

🌸 SYNOPSIS 🌸

struct max3191x_chip {
    struct gpio_chip gpio;
    struct mutex lock;
    u32 nchips;
    enum max3191x_mode mode;
    struct gpio_descs *modesel_pins;
    struct gpio_descs *fault_pins;
    struct gpio_descs *db0_pins;
    struct gpio_descs *db1_pins;
    struct spi_message mesg;
    struct spi_transfer xfer;
    unsigned long *crc_error;
    unsigned long *overtemp;
    unsigned long *undervolt1;
    unsigned long *undervolt2;
    unsigned long *fault;
    bool ignore_uv;
};

💖 Members 💖

the whole squad, one member at a time 🫶

• gpio — the GPIO controller struct. main character energy, honestly ✨
• lock — this one protects read sequences. it's giving bouncer at the club 🚪💅
• nchips — how many chips are in the daisy-chain. count 'em, bestie 🔢
• mode — the current mode: 0 for 16-bit, 1 for 8-bit. and for simplicity, all chips in the daisy-chain are assumed to use the same mode (no mixing, we don't do that here 🙅‍♀️)
• modesel_pins — GPIO pins to configure modesel of each chip 🎛️
• fault_pins — GPIO pins to detect fault of each chip 🚨
• db0_pins — GPIO pins to configure debounce of each chip 🎚️
• db1_pins — GPIO pins to configure debounce of each chip 🎚️ (yep, db1_pins has the exact same description as db0_pins — that's what it says, not me making stuff up, i'm just the messenger 😭)
• mesg — the SPI message used to perform a readout 📨
• xfer — the SPI transfer used by mesg 🔁
• crc_error — bitmap signaling CRC error for each chip 💀
• overtemp — bitmap signaling overtemperature alarm for each chip 🔥
• undervolt1 — bitmap signaling undervoltage alarm for each chip ⚡
• undervolt2 — bitmap signaling undervoltage warning for each chip ⚠️
• fault — bitmap signaling assertion of fault_pins for each chip 🚩
• ignore_uv — whether to ignore undervoltage alarms. it gets set by a device property if the chips are powered through 5VOUT instead of VCC24V, and in that case they will constantly signal undervoltage (iconic behavior, honestly 😭). and again, for simplicity, all chips in the daisy-chain are assumed to be powered the same way 🔌

lowkey important: those "for simplicity" bits are real constraints, not vibes. the struct assumes uniform mode and uniform powering across the whole chain. periodt. 👑

🦋 SEE ALSO 🦋

• Kernel file ./drivers/gpio/gpio-max3191x.c — go read the source, bestie, it's right there 📖✨

and that's the whole page, no cap 💜 huge shoutout to the ./drivers/gpio crew — this one's dated October 2026, manual name Kernel API Manual, so go off and read those registers responsibly, mwah 🎀🌸💅