STRUCT ETR_BUF(9)

💖 struct etr_buf(9) 💖

okay so bestie, welcome to the kernel API manual — this page is literally all about struct etr_buf, which is the details of the buffer used by ETR. and there's a second bit glued onto the NAME line too: it's also the refcount — the number of sources currently using this etr_buf. two-for-one deal, we love that for us 🎀

✨ SYNOPSIS ✨

like, here's the whole vibe of the struct, character for character, don't @ me:

struct etr_buf {
    refcount_t refcount;
    enum etr_mode                   mode;
    bool full;
    ssize_t size;
    dma_addr_t hwaddr;
    unsigned long                   offset;
    s64 len;
    const struct etr_buf_operations *ops;
    void *private;
 };

🌸 Members 🌸

so these are the fields, and yes they all have main character energy in their own way:

• mode — the mode of the ETR buffer. contiguous, Scatter Gather, etc. it's giving "which flavor of buffer are we today" 💅
• full — trace data overflow. that's it, that's the whole thing. it's a bool and it says "yep we spilled" 💀
• size — the size of the buffer. iconic, self-explanatory, no notes.
• hwaddr — the address to be programmed in the TMC:DBA{LO,HI}. hardware address, we're talking to the actual silicon 🦋
• offset — the offset of the trace data in the buffer for consumption. like where you start reading, iykyk.
• len — available trace data buf (may round up to the beginning). yes it might wrap around to the start, lowkey unhinged but that's the deal 🙈
• ops — ETR buffer operations for the mode. the function table bestie, this is where the behavior lives ✨
• private — backend specific information for the buf. the mystery box, the lore, the "don't touch unless you know" 🫶

ngl the refcount field lives up there in the struct but the member list doesn't spell it out separately — it's the one from the NAME line, the number of sources currently using this etr_buf. just so you're not confused, queen 💖

🦋 SEE ALSO 🦋

• Kernel file ./drivers/hwtracing/coresight/coresight-tmc.h
• struct tmc_drvdata(9)
• struct tmc_pages(9)

like go read those next, they're the supporting cast and they absolutely ate 👑

and that's the whole page, periodt. this little icon dropped from ./drivers/hwtracing/coresight, dated October 2026 — mwah, look at her go 🌈⭐💜