STRUCT DRM_I915_QUERY_MEMORY_REGIONS(9)

💖 struct drm_i915_query_memory_regions(9) 💖

okay so bestie, welcome to the Kernel API Manual — this page is literally all about struct drm_i915_query_memory_regions, and by the end you're gonna know it like the back of your hand. no cap. 🦋

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✨ NAME ✨

struct drm_i915_query_memory_regions — yeah so the page header just gives you the struct name and dips, that's it, that's the whole NAME section 🙈 (there's genuinely no description tagline after the dash, so don't come for me)

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⭐ SYNOPSIS ⭐

the whole shape of it, bestie, look:

struct drm_i915_query_memory_regions {
    __u32 num_regions;
    __u32 rsvd[3];
    struct drm_i915_memory_region_info regions[];
 };

like... three fields, one of them flexes an unsized array, we love a growable moment 👑

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💅 Members 💅

• num_regions — the number of supported regions. the headcount. how many besties are in this region group chat 💖
• rsvd — MBZ, which means Must Be Zero. do not touch. do not decorate. leave it at zero, periodt. 🫶
• regions — the actual tea ☕ — info about each supported region, one struct per region.

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🌸 Description 🌸

okay so here's the vibe: the region info query is how you get the driver to list every region it knows about. it does that by filling in an array of struct drm_i915_memory_region_info structures. that's it, that's the whole job. it's giving census, but for memory regions 🧚

and here's the literal example for getting the list of supported regions, i did not change a single character because this is sacred code:

struct drm_i915_query_memory_regions *info;
struct drm_i915_query_item item = {
        .query_id = DRM_I915_QUERY_MEMORY_REGIONS;
};
struct drm_i915_query query = {
        .num_items = 1,
        .items_ptr = (uintptr_t)item,
};
int err, i;

// First query the size of the blob we need, this needs to be large
// enough to hold our array of regions. The kernel will fill out the
// item.length for us, which is the number of bytes we need.
err = ioctl(fd, DRM_IOCTL_I915_QUERY, query);
if (err) ...

info = calloc(1, item.length);
// Now that we allocated the required number of bytes, we call the ioctl
// again, this time with the data_ptr pointing to our newly allocated
// blob, which the kernel can then populate with the all the region info.
item.data_ptr = (uintptr_t)info,

err = ioctl(fd, DRM_IOCTL_I915_QUERY, query);
if (err) ...

// We can now access each region in the array
for (i = 0; i < info->num_regions; i++) {
        struct drm_i915_memory_region_info mr = info->regions[i];
        u16 class = mr.region.class;
        u16 instance = mr.region.instance;

        ....
}

free(info);

the way this works is a two-pass situation, and honestly? iconic. 🎀

1. first ioctl(fd, DRM_IOCTL_I915_QUERY, query) call — you're just asking "how many bytes do i need?" the kernel fills out item.length for you with the exact byte count. no guessing required, it literally tells you. 💫
2. then info = calloc(1, item.length); — allocate that many bytes, slay.
3. then you set item.data_ptr = (uintptr_t)info, and hit the same ioctl(fd, DRM_IOCTL_I915_QUERY, query) again — this time the kernel populates your freshly allocated blob with all the region info. ate and left no crumbs 🔥
4. then you loop for (i = 0; i < info->num_regions; i++), grab each struct drm_i915_memory_region_info mr = info->regions[i];, and read mr.region.class and mr.region.instance into your u16s. main character data extraction moment 👑
5. and obviously free(info); — memory hygiene is self care, bestie, do not leak 🫧

ngl both ioctl calls check if (err) ... — please actually handle your errors, i'm begging 🙏 the ... is a placeholder, not a lifestyle.

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🦋 SEE ALSO 🦋

the whole friend group, in order, exactly as listed — go say hi to all of them:

• Kernel file ./tools/perf/trace/beauty/include/uapi/drm/i915_drm.h
• uevents generated by i915 on its device node(9)
• struct i915_user_extension(9)
• enum drm_i915_gem_engine_class(9)
• struct i915_engine_class_instance(9)
• perf_events exposed by i915 through /sys/bus/event_sources/drivers/i915(9)
• struct drm_i915_getparam(9)
• drm_i915_getparam_t(9)
• struct drm_i915_gem_mmap_offset(9)
• struct drm_i915_gem_set_domain(9)
• struct drm_i915_gem_exec_fence(9)
• struct drm_i915_gem_execbuffer_ext_timeline_fences(9)
• struct drm_i915_gem_execbuffer2(9)
• struct drm_i915_gem_caching(9)
• struct drm_i915_gem_context_create_ext(9)
• struct drm_i915_gem_context_param(9)
• Virtual Engine uAPI(9)
• struct i915_context_engines_parallel_submit(9)
• Context Engine Map uAPI(9)
• struct drm_i915_gem_context_create_ext_setparam(9)
• struct drm_i915_gem_vm_control(9)
• struct drm_i915_gem_userptr(9)
• struct drm_i915_perf_oa_config(9)
• struct drm_i915_query_item(9)
• struct drm_i915_query(9)
• struct drm_i915_query_topology_info(9)
• Engine Discovery uAPI(9)
• struct drm_i915_engine_info(9)
• struct drm_i915_query_engine_info(9)
• struct drm_i915_query_perf_config(9)
• enum drm_i915_gem_memory_class(9)
• struct drm_i915_gem_memory_class_instance(9)
• struct drm_i915_memory_region_info(9)
• struct drm_i915_query_guc_submission_version(9)
• GuC HWCONFIG blob uAPI(9)
• struct drm_i915_gem_create_ext(9)
• struct drm_i915_gem_create_ext_memory_regions(9)
• struct drm_i915_gem_create_ext_protected_content(9)
• struct drm_i915_gem_create_ext_set_pat(9)

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ok and one last thing — the footer on this page shows the source as ./tools/perf/trace/beauty/incl... (yep, truncated like that in the original, not me being lazy 💀) and the date is October 2026. so that's the version deets, mwah, go query some regions bestie, you're gonna do amazing 💜✨🌈