STRUCT I2C_GPIO_PLATFORM_DATA(9)

💖 NAME 💖

struct i2c_gpio_platform_data — the platform-dependent data for i2c-gpio, aka the little bundle of settings that tells the bit-banged I2C driver how your particular pins actually behave 💅

(and yes bestie, this is from the Kernel API Manual, section 9, we love a kernel reference page 🎀)

✨ SYNOPSIS ✨

struct i2c_gpio_platform_data {
    int udelay;
    int timeout;
    unsigned int    sda_is_open_drain:1;
    unsigned int    sda_is_output_only:1;
    unsigned int    sda_has_no_pullup:1;
    unsigned int    scl_is_open_drain:1;
    unsigned int    scl_is_output_only:1;
    unsigned int    scl_has_no_pullup:1;
 };

okay so it's literally one int, another int, and then six single-bit flags — the bitfields are doing main character energy here 🫶

👑 Members 👑

• udelay — the signal toggle delay ⏱️. the SCL frequency is (500 / udelay) kHz, so yeah, that's the whole vibe: pick your delay, get your clock speed. math is mathing 🔥
• timeout — clock stretching timeout, measured in jiffies 🕰️. if the slave keeps SCL low for longer than this, the transfer will time out. no cap, it will just give up on you 😭
• sda_is_open_drain — SDA is configured as open drain, i.e. the pin isn't actively driven high when setting the output value high. gpio_get_value must return the actual pin state even if the pin is configured as an output 👀. so like… you can't just lie to yourself about the pin state, the read has to be honest fr fr.
• sda_is_output_only — SDA output drivers can't be turned off 🚫. this one's for clients that can only read SDA/SCL — they're not doing bidirectional, they're just reading, and that's valid 💅
• sda_has_no_pullup — SDA is used in a non-compliant way and has no pull-up 🙈. therefore disable open-drain. yes it's sketchy, yes the flag exists for exactly this, no we're not judging you (we're judging a little).
• scl_is_open_drain — SCL is set up as open drain ⚡. same requirements as for sda_is_open_drain apply — so re-read that one, bestie, it's a package deal 👑
• scl_is_output_only — SCL output drivers cannot be turned off 🔒. that's it, that's the flag.
• scl_has_no_pullup — SCL is used in a non-compliant way and has no pull-up 🌸. therefore disable open-drain. twin of the SDA one, matching set, iconic 🎀

🌈 SEE ALSO 🌈

• Kernel file ./include/linux/platform_data/i2c-gpio.h — go read the actual header, it's right there, iykyk 📖✨

real talk: those *_has_no_pullup flags are literally the code admitting the hardware is non-compliant. keep that in mind before you ship it 🫶

okay that's the whole page, you ate that 🍓 this gem lives in ./include/linux/platform_data and the version stamp on it is October 2026 — so go forth, configure your GPIO I2C pins, and slay 💜✨