STRUCT EP93XX_SPI(9)

💖 struct ep93xx_spi(9) 💖

okay so first things first, bestie: this is a page from the Kernel API Manual, and it's literally all about struct ep93xx_spi, aka the EP93xx SPI controller structure. yes, the actual struct. the whole vibe is "here's the struct, here's every field, don't touch anything you don't understand." iconic behavior honestly 🎀

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✨ NAME ✨

struct ep93xx_spi — the EP93xx SPI controller structure, no cap 🦋

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🌸 SYNOPSIS 🌸

here's the whole thing, character for character, do NOT come for me about the alignment:

struct ep93xx_spi {
    struct clk                      *clk;
    void __iomem                    *mmio;
    unsigned long                   sspdr_phys;
    size_t tx;
    size_t rx;
    size_t fifo_level;
    struct dma_chan                 *dma_rx;
    struct dma_chan                 *dma_tx;
    struct sg_table                 rx_sgt;
    struct sg_table                 tx_sgt;
    void *zeropage;
 };

she's got range, she's got pointers, she's got a void * at the end like a little mystery 🕵️‍♀️

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💅 Members 💅

okay now the part you actually came for — the member-by-member breakdown. every single one. let's go 🔥

• clk — the clock for the controller. the heartbeat. the main character energy of the whole struct ⏰
• mmio — pointer to the ioremap'd registers. that's where the actual hardware lives, bestie, so handle with care 🫶
• sspdr_phys — the physical address of the SSPDR register. like a home address but for a register 🏠
• tx — the current byte in the transfer that needs to transmit. she's sending 📤
• rx — the current byte in the transfer that needs to receive. she's receiving 📥
• fifo_level — how full is FIFO, and the range is literally 0..SPI_FIFO_SIZE - 1. important detail: receiving one frame decreases this level and sending one frame increases it. yes that's the actual direction, don't @ me 💀
• dma_rx — the RX DMA channel. she receives, but make it hardware 🌈
• dma_tx — the TX DMA channel. she transmits, but make it hardware ✨
• rx_sgt — the sg table for RX transfers. the receipts, organized 🧾
• tx_sgt — the sg table for TX transfers. the other receipts, also organized 🧾
• zeropage — a dummy page used as the RX buffer when only the TX buffer is passed in by the client. a little stand-in, a little understudy, a little "we move" 🎭

fr fr though: fifo_level is the one to keep your eyes on. receive one frame, level goes down. send one frame, level goes up. that's the whole mechanic, memorise it 👑

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🦋 SEE ALSO 🦋

go read these next, iykyk:

• Kernel file ./drivers/spi/spi-ep93xx.c ep93xx_spi_calc_divisors(9), ep93xx_spi_read_write(9), ep93xx_spi_dma_prepare(9), ep93xx_spi_dma_finish(9)

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that's the whole page, bestie, you ate it up 💖 this little masterpiece lives in ./drivers/spi, dated October 2026, and it's filed under struct ep93xx_spi(9) — anyway mwah, go read your kernel source, periodt 💅🌸