STRUCT QDR(9)

💅 struct qdr(9) — the queue description record glow-up

okay bestie, buckle up, we're reading struct qdr(9) from the Kernel API Manual and honestly? it's giving "backstage pass to the queue" energy. QDR = queue description record, and it's the little blueprint that tells you everything about a queue's format, sizes, addresses and key. no cap, it's iconic. 🎀

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✨ NAME ✨

struct qdr — queue description record (QDR). that's it, that's the whole vibe. 🦋

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🌸 SYNOPSIS 🌸

here's the whole thing, copied exactly, don't @ me:

struct qdr {
    u32 qfmt   : 8;
    u32 : 16;
    u32 ac     : 8;
    u32 : 8;
    u32 iqdcnt : 8;
    u32 : 8;
    u32 oqdcnt : 8;
    u32 : 8;
    u32 iqdsz  : 8;
    u32 : 8;
    u32 oqdsz  : 8;
    dma64_t qiba;
    u32 : 32;
    u32 qkey   : 4;
    u32 : 28;
    struct qdesfmt0 qdf0[126];
 };

like, look at all those anonymous bit-field gaps (: 16, : 8, : 32, : 28…). they're not filler, they're padding, and they are serving structure. periodt. 💅

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👑 Members 👑

bestie, let's go member by member, no skipping, we don't do that here:

• qfmt — queue format. the whole personality of the queue in one field. ✨
• ac — adapter characteristics. the adapter's little resume of traits. 🫶
• iqdcnt — input queue descriptor count. how many input descriptors we're working with. 🍓
• oqdcnt — output queue descriptor count. same energy, but output. 🌸
• iqdsz — input queue descriptor size. the size, for the input side. 💜
• oqdsz — output queue descriptor size. the size, for the output side. 💜
• qiba — absolute address of queue information block. a whole absolute address, main character energy. 🔥
• qkey — queue information block key. it's a 4-bit key and it's lowkey important. 🔑 (well, : 4 bits important.)
• qdf0 — queue descriptions. an array [126] of struct qdesfmt0, and yes, 126 of them, we counted. 🌈

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🦋 SEE ALSO 🦋

the friend group!! go say hi, they all live in Kernel file ./arch/s390/include/asm/qdio.h:

• struct qdesfmt0(9)
• struct qib(9)
• struct slibe(9)
• struct qaob(9)
• struct slib(9)
• struct qdio_buffer_element(9)
• struct qdio_buffer(9)
• struct sl_element(9)
• struct sl(9)
• struct slsb(9)
• struct qdio_initialize(9)

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ngl, if you're touching queues on s390 you're gonna want to read these. iykyk. 💀

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and that's the page!! mwah 💖 this one came from ./arch/s390/include/asm, dated October 2026, and it's struct qdr(9) forever and always. slay, go read your headers. 🧚‍♀️⭐