i915_perf_read(9)

💖 i915_perf_read(9) 💖

okay bestie, so this is i915_perf_read(9) from the Kernel API Manual — and it's literally the entry point for handling a read() FOP on i915 perf stream FDs, no cap. Let me walk you through it 🫶

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✨ SYNOPSIS ✨

ssize_t i915_perf_read (struct file *file , char __user *buf , size_t
count , loff_t *ppos );

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🎀 ARGUMENTS 🎀

• file — an i915 perf stream file, periodt
• buf — the destination buffer, handed to us by userspace 🦋
• count — how many bytes userspace is trying to read, iykyk
• ppos — (inout) the file seek position — and honestly, it's not even used 🙈

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🌸 DESCRIPTION 🌸

So this is the entry point for handling a read on a stream file descriptor from userspace. Most of the actual work is lowkey left to i915_perf_read_locked and i915_perf_stream_ops->read — but here's the thing: to save having stream implementations (of which we might have multiple later, fr fr) we handle the blocking read right here ✨

We can also consistently treat trying to read from a disabled stream as an IO error, so implementations can totally assume the stream is enabled while reading. Iconic behaviour tbh 💅

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🔥 RETURN 🔥

The number of bytes copied, or a negative error code if something goes wrong 😭

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👑 SEE ALSO 👑

Kernel file ./drivers/gpu/drm/i915/i915_perf.c — plus the whole friend group:

• i915 Perf Overview(9)
• i915 Perf History and Comparison with Core Perf(9)
• OA Tail Pointer Race(9)
• struct perf_open_properties(9)
• oa_buffer_check_unlocked(9)
• append_oa_status(9)
• append_oa_sample(9)
• gen8_append_oa_reports(9)
• gen8_oa_read(9)
• gen7_append_oa_reports(9)
• gen7_oa_read(9)
• i915_oa_wait_unlocked(9)
• i915_oa_poll_wait(9)
• i915_oa_read(9)
• oa_get_render_ctx_id(9)
• oa_put_render_ctx_id(9)
• i915_oa_stream_enable(9)
• i915_oa_stream_disable(9)
• i915_oa_stream_init(9)
• i915_perf_poll_locked(9)
• i915_perf_poll(9)
• i915_perf_enable_locked(9)
• i915_perf_disable_locked(9)
• i915_perf_ioctl_locked(9)
• i915_perf_ioctl(9)
• i915_perf_destroy_locked(9)
• i915_perf_release(9)
• i915_perf_open_ioctl_locked(9)
• read_properties_unlocked(9)
• i915_perf_open_ioctl(9)
• i915_perf_register(9)
• i915_perf_unregister(9)
• i915_perf_add_config_ioctl(9)
• i915_perf_remove_config_ioctl(9)
• i915_perf_init(9)
• i915_perf_fini(9)
• i915_perf_ioctl_version(9)

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and that's the whole page, bestie 💜 this one's brought to you by the fine people at ./drivers/gpu/drm/i915, dated October 2026 — mwah, slay, see u in the next manpage 🎀✨💅