etm4_cfg_map_reg_offset(9)

💅 etm4_cfg_map_reg_offset — like, the kernel API manual page, bestie

okay so before we even get into it: this is etm4_cfg_map_reg_offset(9) from the Kernel API Manual, and it is genuinely one of those little functions that's out here doing the most important gatekeeping job ever. ✨

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🌸 NAME 🌸

etm4_cfg_map_reg_offset — no cap, her whole job is to validate and map the register offset into a location in the driver config struct. that's it. that's the vibe check. 🔥

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🎀 SYNOPSIS 🎀

int etm4_cfg_map_reg_offset (struct etmv4_drvdata *drvdata , struct
       cscfg_regval_csdev *reg_csdev , u32 offset );

three args, one int return, absolutely iconic behaviour. 🫶

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🦋 ARGUMENTS 🦋

• drvdata — the driver data to map into. this is the main character, everything's going in here. 👑
• reg_csdev — the register to map. the little guy getting placed. 🎀
• offset — the device offset for the register. lowkey the address of where things live. 💅

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⭐ DESCRIPTION ⭐

so here's what she actually does:

• limits the number of registers that can be accessed and programmed in features, to just the ones that are used to control the trace capture parameters. not everything gets in, we're being selective. 💅
• omits or limits access to the ones that the driver must use exclusively. those are hers. periodt. 🔒
• and if you come at her with an invalid offset? it's giving fail code return, and then a feature load failure. so like, don't. 😭

ngl, an invalid offset isn't a "whoops, try again" moment — you get a fail code return, and the feature load fails. no gentle vibes, just consequences. 💀

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🌈 SEE ALSO 🌈

• Kernel file ./drivers/hwtracing/coresight/coresight-etm4x-cfg.c — go read her, iykyk 🧚
• etm4_cfg_load_feature(9) — her bestie fr fr 🌸

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and that's the page!! source/version is ./drivers/hwtracing/coresight, dated October 2026 — so yeah, she's from the future, obviously. 🦋⭐ mwah, go read the source, love u bye 💖