scm_legacy_call(9)

💅 scm_legacy_call(9) — the Kernel API Manual, but make it make sense 🫶

okay so this is a page from the Kernel API Manual and it's all about scm_legacy_call, which is genuinely iconic in a "talks to the secure world for you" kinda way 👑

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🌸 NAME 🌸

scm_legacy_call — sends a command to the SCM and then waits for that command to finish processing. yes bestie, it blocks, she's a patient queen 💅

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✨ SYNOPSIS ✨

int scm_legacy_call (struct device *dev , const struct qcom_scm_desc
*desc , struct qcom_scm_res *res );

that's the whole vibe: you hand her a device, a descriptor, and somewhere to put the results ✨

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🎀 ARGUMENTS 🎀

• dev — the device. that's it, that's the whole description, she's literally just the device 🫶
• desc — the descriptor structure, and she's the main character here because she carries both the arguments going in and the return values coming out 📥📤
• res — the results from the SMC call. this is where the tea gets reported back to you 🍓

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🔥 DESCRIPTION 🔥

okay so there's a very important note on cache maintenance, and ngl you cannot skip this part, it's giving "final boss of the fine print" 💀

Any buffers that are expected to be accessed by the secure world must be flushed before invoking qcom_scm_call and invalidated in the cache immediately after qcom_scm_call returns. Cache maintenance on the command and response buffers is taken care of by qcom_scm_call — however, callers are responsible for any other cached buffers passed over to the secure world.

so like, qcom_scm_call has your back for the command buffer and the response buffer (she's an angel 😇), but every other cached buffer you yeet over to the secure world? that's on you, bestie. flush before, invalidate after, no cap 🧚✨

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👑 SEE ALSO 👑

• Kernel file ./drivers/firmware/qcom/qcom_scm-legacy.c — go read the source, iykyk 📖
• struct arm_smccc_args(9)
• struct scm_legacy_command(9)
• struct scm_legacy_response(9)
• scm_legacy_command_to_response(9)
• scm_legacy_get_command_buffer(9)
• scm_legacy_get_response_buffer(9)
• scm_legacy_call_atomic(9) — the atomic sibling, she does not wait around, different energy entirely ⚡

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kisses from ./drivers/firmware/qcom, dated October 2026 — that's the version and the date, and honestly? she ate. periodt. 🌈💖