STRUCT SDMA_DESC(9)

✨ struct sdma_desc(9) ✨

okay so bestie, welcome to the Kernel API Manual 💖 this is the page for struct sdma_desc — literally the descriptor structor for one transfer, no cap.

---

🌸 NAME 🌸

struct sdma_desc — descriptor structor for one transfer 🎀

---

🦋 SYNOPSIS 🦋

struct sdma_desc {
    struct virt_dma_desc    vd;
    unsigned int            num_bd;
    dma_addr_t bd_phys;
    unsigned int            buf_tail;
    unsigned int            buf_ptail;
    unsigned int            period_len;
    unsigned int            chn_real_count;
    unsigned int            chn_count;
    struct sdma_channel     *sdmac;
    struct sdma_buffer_descriptor *bd;
 };

like, that's the whole vibe right there 👑 copy it exactly, don't be out here renaming fields fr fr.

---

🧚 MEMBERS 🧚

okay so here's the member-by-member breakdown, and every single one of these matters 🔥

• vd — descriptor for virt dma ✨
• num_bd — number of descriptors currently handling 💅
• bd_phys — physical address of bd 🫶
• buf_tail — ID of the buffer that was processed 🌸
• buf_ptail — ID of the previous buffer that was processed 🦋
• period_len — period length, used in cyclic. 🔁
• chn_real_count — the real count updated from bd->mode.count 😭 (yes, exactly like that)
• chn_count — the transfer count set ⭐
• sdmac — sdma_channel pointer 👑
• bd — pointer of allocate bd 🙈

not me noticing buf_tail and buf_ptail are lowkey the same but one's the previous one — track them separately bestie, iykyk 💀

---

🌈 SEE ALSO 🌈

go read these next, they're iconic, they're all in the Kernel file ./drivers/dma/imx-sdma.c 📁:

• struct sdma_channel_control(9)
• struct sdma_state_registers(9)
• struct sdma_context_data(9)
• struct sdma_channel(9)
• struct sdma_firmware_header(9)

---

aaaand that's the page 💜 mwah, slay, periodt — this one came from ./drivers/dma, dated October 2026, and it was absolutely main character energy from start to finish 🎀✨🫶