diff mbox

[v13,5/6] drm/i915: add query uAPI

Message ID 20180215120203.23115-6-lionel.g.landwerlin@intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Lionel Landwerlin Feb. 15, 2018, 12:02 p.m. UTC 
There are a number of information that are readable from hardware
registers and that we would like to make accessible to userspace. One
particular example is the topology of the execution units (how are
execution units grouped in subslices and slices and also which ones
have been fused off for die recovery).

At the moment the GET_PARAM ioctl covers some basic needs, but
generally is only able to return a single value for each defined
parameter. This is a bit problematic with topology descriptions which
are array/maps of available units.

This change introduces a new ioctl that can deal with requests to fill
structures of potentially variable lengths. The user is expected fill
a query with length fields set at 0 on the first call, the kernel then
sets the length fields to the their expected values. A second call to
the kernel with length fields at their expected values will trigger a
copy of the data to the pointed memory locations.

The scope of this uAPI is only to provide information to userspace,
not to allow configuration of the device.

v2: Simplify dispatcher code iteration (Tvrtko)
    Tweak uapi drm_i915_query_item structure (Tvrtko)

v3: Rename pad fields into flags (Chris)
    Return error on flags field != 0 (Chris)
    Only copy length back to userspace in drm_i915_query_item (Chris)

v4: Use array of functions instead of switch (Chris)

v5: More comments in uapi (Tvrtko)
    Return query item errors in length field (All)

v6: Tweak uapi comments style to match the coding style (Lionel)

v7: Add i915_query.h (Joonas)

v8: (Lionel) Change the behavior of the item iterator to report
    invalid queries into the query item rather than stopping the
    iteration. This enables userspace applications to query newer
    items on older kernels and only have failure on the items that are
    not supported.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
---
 drivers/gpu/drm/i915/Makefile     |  1 +
 drivers/gpu/drm/i915/i915_drv.c   |  2 ++
 drivers/gpu/drm/i915/i915_query.c | 67 +++++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_query.h | 33 +++++++++++++++++++
 include/uapi/drm/i915_drm.h       | 41 ++++++++++++++++++++++++
 5 files changed, 144 insertions(+)
 create mode 100644 drivers/gpu/drm/i915/i915_query.c
 create mode 100644 drivers/gpu/drm/i915/i915_query.h

Comments

Tvrtko Ursulin Feb. 20, 2018, 10:58 a.m. UTC | #1 
On 15/02/2018 12:02, Lionel Landwerlin wrote:
> There are a number of information that are readable from hardware
> registers and that we would like to make accessible to userspace. One
> particular example is the topology of the execution units (how are
> execution units grouped in subslices and slices and also which ones
> have been fused off for die recovery).
> 
> At the moment the GET_PARAM ioctl covers some basic needs, but
> generally is only able to return a single value for each defined
> parameter. This is a bit problematic with topology descriptions which
> are array/maps of available units.
> 
> This change introduces a new ioctl that can deal with requests to fill
> structures of potentially variable lengths. The user is expected fill
> a query with length fields set at 0 on the first call, the kernel then
> sets the length fields to the their expected values. A second call to
> the kernel with length fields at their expected values will trigger a
> copy of the data to the pointed memory locations.
> 
> The scope of this uAPI is only to provide information to userspace,
> not to allow configuration of the device.
> 
> v2: Simplify dispatcher code iteration (Tvrtko)
>      Tweak uapi drm_i915_query_item structure (Tvrtko)
> 
> v3: Rename pad fields into flags (Chris)
>      Return error on flags field != 0 (Chris)
>      Only copy length back to userspace in drm_i915_query_item (Chris)
> 
> v4: Use array of functions instead of switch (Chris)
> 
> v5: More comments in uapi (Tvrtko)
>      Return query item errors in length field (All)
> 
> v6: Tweak uapi comments style to match the coding style (Lionel)
> 
> v7: Add i915_query.h (Joonas)
> 
> v8: (Lionel) Change the behavior of the item iterator to report
>      invalid queries into the query item rather than stopping the
>      iteration. This enables userspace applications to query newer
>      items on older kernels and only have failure on the items that are
>      not supported.
> 
> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
> ---
>   drivers/gpu/drm/i915/Makefile     |  1 +
>   drivers/gpu/drm/i915/i915_drv.c   |  2 ++
>   drivers/gpu/drm/i915/i915_query.c | 67 +++++++++++++++++++++++++++++++++++++++
>   drivers/gpu/drm/i915/i915_query.h | 33 +++++++++++++++++++
>   include/uapi/drm/i915_drm.h       | 41 ++++++++++++++++++++++++
>   5 files changed, 144 insertions(+)
>   create mode 100644 drivers/gpu/drm/i915/i915_query.c
>   create mode 100644 drivers/gpu/drm/i915/i915_query.h
> 
> diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> index f55cc028b2eb..e8e25bb3af81 100644
> --- a/drivers/gpu/drm/i915/Makefile
> +++ b/drivers/gpu/drm/i915/Makefile
> @@ -70,6 +70,7 @@ i915-y += i915_cmd_parser.o \
>   	  i915_gem_timeline.o \
>   	  i915_gem_userptr.o \
>   	  i915_gemfs.o \
> +	  i915_query.o \
>   	  i915_trace_points.o \
>   	  i915_vma.o \
>   	  intel_breadcrumbs.o \
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index 47c9f5a7e6c4..18350620cd06 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -49,6 +49,7 @@
>   #include "i915_drv.h"
>   #include "i915_trace.h"
>   #include "i915_pmu.h"
> +#include "i915_query.h"
>   #include "i915_vgpu.h"
>   #include "intel_drv.h"
>   #include "intel_uc.h"
> @@ -2836,6 +2837,7 @@ static const struct drm_ioctl_desc i915_ioctls[] = {
>   	DRM_IOCTL_DEF_DRV(I915_PERF_OPEN, i915_perf_open_ioctl, DRM_RENDER_ALLOW),
>   	DRM_IOCTL_DEF_DRV(I915_PERF_ADD_CONFIG, i915_perf_add_config_ioctl, DRM_UNLOCKED|DRM_RENDER_ALLOW),
>   	DRM_IOCTL_DEF_DRV(I915_PERF_REMOVE_CONFIG, i915_perf_remove_config_ioctl, DRM_UNLOCKED|DRM_RENDER_ALLOW),
> +	DRM_IOCTL_DEF_DRV(I915_QUERY, i915_query_ioctl, DRM_UNLOCKED|DRM_RENDER_ALLOW),
>   };
>   
>   static struct drm_driver driver = {
> diff --git a/drivers/gpu/drm/i915/i915_query.c b/drivers/gpu/drm/i915/i915_query.c
> new file mode 100644
> index 000000000000..92ce3e24588e
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/i915_query.c
> @@ -0,0 +1,67 @@
> +/*
> + * Copyright © 2017 Intel Corporation
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
> + * IN THE SOFTWARE.
> + *
> + */
> +
> +#include "i915_drv.h"
> +#include <uapi/drm/i915_drm.h>
> +
> +static int (* const i915_query_funcs[])(struct drm_i915_private *dev_priv,
> +					struct drm_i915_query_item *query_item) = {
> +};
> +
> +int i915_query_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
> +{
> +	struct drm_i915_private *dev_priv = to_i915(dev);
> +	struct drm_i915_query *args = data;
> +	struct drm_i915_query_item __user *user_item_ptr =
> +		u64_to_user_ptr(args->items_ptr);
> +	u32 i;
> +
> +	if (args->flags != 0)
> +		return -EINVAL;
> +
> +	for (i = 0; i < args->num_items; i++, user_item_ptr++) {
> +		struct drm_i915_query_item item;
> +		u64 func_idx;
> +		int ret;
> +
> +		if (copy_from_user(&item, user_item_ptr, sizeof(item)))
> +			return -EFAULT;
> +
> +		if (item.query_id == 0)
> +			return -EINVAL;
> +
> +		func_idx = item.query_id - 1;
> +
> +		if (func_idx < ARRAY_SIZE(i915_query_funcs))
> +			ret = i915_query_funcs[func_idx](dev_priv, &item);
> +		else
> +			ret = -EINVAL;
> +
> +		/* Only write the length back to userspace if they differ. */
> +		if (ret != item.length && put_user(ret, &user_item_ptr->length))
> +			return -EFAULT;
> +	}
> +
> +	return 0;
> +}
> diff --git a/drivers/gpu/drm/i915/i915_query.h b/drivers/gpu/drm/i915/i915_query.h
> new file mode 100644
> index 000000000000..4550e8f21459
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/i915_query.h
> @@ -0,0 +1,33 @@
> +/*
> + * Copyright © 2017 Intel Corporation
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
> + * IN THE SOFTWARE.
> + *
> + */
> +
> +#ifndef _I915_QUERY_H_
> +#define _I915_QUERY_H_
> +
> +struct drm_device;
> +struct drm_file;
> +
> +int i915_query_ioctl(struct drm_device *dev, void *data, struct drm_file *file);
> +
> +#endif
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index 29fa48e4755d..7fd980176f25 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h
> @@ -318,6 +318,7 @@ typedef struct _drm_i915_sarea {
>   #define DRM_I915_PERF_OPEN		0x36
>   #define DRM_I915_PERF_ADD_CONFIG	0x37
>   #define DRM_I915_PERF_REMOVE_CONFIG	0x38
> +#define DRM_I915_QUERY			0x39
>   
>   #define DRM_IOCTL_I915_INIT		DRM_IOW( DRM_COMMAND_BASE + DRM_I915_INIT, drm_i915_init_t)
>   #define DRM_IOCTL_I915_FLUSH		DRM_IO ( DRM_COMMAND_BASE + DRM_I915_FLUSH)
> @@ -375,6 +376,7 @@ typedef struct _drm_i915_sarea {
>   #define DRM_IOCTL_I915_PERF_OPEN	DRM_IOW(DRM_COMMAND_BASE + DRM_I915_PERF_OPEN, struct drm_i915_perf_open_param)
>   #define DRM_IOCTL_I915_PERF_ADD_CONFIG	DRM_IOW(DRM_COMMAND_BASE + DRM_I915_PERF_ADD_CONFIG, struct drm_i915_perf_oa_config)
>   #define DRM_IOCTL_I915_PERF_REMOVE_CONFIG	DRM_IOW(DRM_COMMAND_BASE + DRM_I915_PERF_REMOVE_CONFIG, __u64)
> +#define DRM_IOCTL_I915_QUERY			DRM_IOWR(DRM_COMMAND_BASE + DRM_I915_QUERY, struct drm_i915_query)
>   
>   /* Allow drivers to submit batchbuffers directly to hardware, relying
>    * on the security mechanisms provided by hardware.
> @@ -1615,6 +1617,45 @@ struct drm_i915_perf_oa_config {
>   	__u64 flex_regs_ptr;
>   };
>   
> +
> +struct drm_i915_query_item {
> +	__u64 query_id;
> +
> +	/*
> +	 * When set to zero by userspace, this is filled with the size of the
> +	 * data to be written at the data_ptr pointer. The kernel set this
> +	 * value to a negative value to signal an error on a particular query
> +	 * item.
> +	 */
> +	__s32 length;
> +
> +	/*
> +	 * Unused for now.
> +	 */
> +	__u32 flags;
> +
> +	/*
> +	 * Data will be written at the location pointed by data_ptr when the
> +	 * value of length matches the length of the data to be written by the
> +	 * kernel.
> +	 */
> +	__u64 data_ptr;
> +};
> +
> +struct drm_i915_query {
> +	__u32 num_items;
> +
> +	/*
> +	 * Unused for now.
> +	 */
> +	__u32 flags;
> +
> +	/*
> +	 * This point to an array of num_items drm_i915_query_item structures.
> +	 */
> +	__u64 items_ptr;
> +};
> +
>   #if defined(__cplusplus)
>   }
>   #endif
> 

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko
diff mbox

Patch

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index f55cc028b2eb..e8e25bb3af81 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -70,6 +70,7 @@  i915-y += i915_cmd_parser.o \
 	  i915_gem_timeline.o \
 	  i915_gem_userptr.o \
 	  i915_gemfs.o \
+	  i915_query.o \
 	  i915_trace_points.o \
 	  i915_vma.o \
 	  intel_breadcrumbs.o \
diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 47c9f5a7e6c4..18350620cd06 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -49,6 +49,7 @@ 
 #include "i915_drv.h"
 #include "i915_trace.h"
 #include "i915_pmu.h"
+#include "i915_query.h"
 #include "i915_vgpu.h"
 #include "intel_drv.h"
 #include "intel_uc.h"
@@ -2836,6 +2837,7 @@  static const struct drm_ioctl_desc i915_ioctls[] = {
 	DRM_IOCTL_DEF_DRV(I915_PERF_OPEN, i915_perf_open_ioctl, DRM_RENDER_ALLOW),
 	DRM_IOCTL_DEF_DRV(I915_PERF_ADD_CONFIG, i915_perf_add_config_ioctl, DRM_UNLOCKED|DRM_RENDER_ALLOW),
 	DRM_IOCTL_DEF_DRV(I915_PERF_REMOVE_CONFIG, i915_perf_remove_config_ioctl, DRM_UNLOCKED|DRM_RENDER_ALLOW),
+	DRM_IOCTL_DEF_DRV(I915_QUERY, i915_query_ioctl, DRM_UNLOCKED|DRM_RENDER_ALLOW),
 };
 
 static struct drm_driver driver = {
diff --git a/drivers/gpu/drm/i915/i915_query.c b/drivers/gpu/drm/i915/i915_query.c
new file mode 100644
index 000000000000..92ce3e24588e
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_query.c
@@ -0,0 +1,67 @@ 
+/*
+ * Copyright © 2017 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ */
+
+#include "i915_drv.h"
+#include <uapi/drm/i915_drm.h>
+
+static int (* const i915_query_funcs[])(struct drm_i915_private *dev_priv,
+					struct drm_i915_query_item *query_item) = {
+};
+
+int i915_query_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
+{
+	struct drm_i915_private *dev_priv = to_i915(dev);
+	struct drm_i915_query *args = data;
+	struct drm_i915_query_item __user *user_item_ptr =
+		u64_to_user_ptr(args->items_ptr);
+	u32 i;
+
+	if (args->flags != 0)
+		return -EINVAL;
+
+	for (i = 0; i < args->num_items; i++, user_item_ptr++) {
+		struct drm_i915_query_item item;
+		u64 func_idx;
+		int ret;
+
+		if (copy_from_user(&item, user_item_ptr, sizeof(item)))
+			return -EFAULT;
+
+		if (item.query_id == 0)
+			return -EINVAL;
+
+		func_idx = item.query_id - 1;
+
+		if (func_idx < ARRAY_SIZE(i915_query_funcs))
+			ret = i915_query_funcs[func_idx](dev_priv, &item);
+		else
+			ret = -EINVAL;
+
+		/* Only write the length back to userspace if they differ. */
+		if (ret != item.length && put_user(ret, &user_item_ptr->length))
+			return -EFAULT;
+	}
+
+	return 0;
+}
diff --git a/drivers/gpu/drm/i915/i915_query.h b/drivers/gpu/drm/i915/i915_query.h
new file mode 100644
index 000000000000..4550e8f21459
--- /dev/null
+++ b/drivers/gpu/drm/i915/i915_query.h
@@ -0,0 +1,33 @@ 
+/*
+ * Copyright © 2017 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ */
+
+#ifndef _I915_QUERY_H_
+#define _I915_QUERY_H_
+
+struct drm_device;
+struct drm_file;
+
+int i915_query_ioctl(struct drm_device *dev, void *data, struct drm_file *file);
+
+#endif
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 29fa48e4755d..7fd980176f25 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -318,6 +318,7 @@  typedef struct _drm_i915_sarea {
 #define DRM_I915_PERF_OPEN		0x36
 #define DRM_I915_PERF_ADD_CONFIG	0x37
 #define DRM_I915_PERF_REMOVE_CONFIG	0x38
+#define DRM_I915_QUERY			0x39
 
 #define DRM_IOCTL_I915_INIT		DRM_IOW( DRM_COMMAND_BASE + DRM_I915_INIT, drm_i915_init_t)
 #define DRM_IOCTL_I915_FLUSH		DRM_IO ( DRM_COMMAND_BASE + DRM_I915_FLUSH)
@@ -375,6 +376,7 @@  typedef struct _drm_i915_sarea {
 #define DRM_IOCTL_I915_PERF_OPEN	DRM_IOW(DRM_COMMAND_BASE + DRM_I915_PERF_OPEN, struct drm_i915_perf_open_param)
 #define DRM_IOCTL_I915_PERF_ADD_CONFIG	DRM_IOW(DRM_COMMAND_BASE + DRM_I915_PERF_ADD_CONFIG, struct drm_i915_perf_oa_config)
 #define DRM_IOCTL_I915_PERF_REMOVE_CONFIG	DRM_IOW(DRM_COMMAND_BASE + DRM_I915_PERF_REMOVE_CONFIG, __u64)
+#define DRM_IOCTL_I915_QUERY			DRM_IOWR(DRM_COMMAND_BASE + DRM_I915_QUERY, struct drm_i915_query)
 
 /* Allow drivers to submit batchbuffers directly to hardware, relying
  * on the security mechanisms provided by hardware.
@@ -1615,6 +1617,45 @@  struct drm_i915_perf_oa_config {
 	__u64 flex_regs_ptr;
 };
 
+
+struct drm_i915_query_item {
+	__u64 query_id;
+
+	/*
+	 * When set to zero by userspace, this is filled with the size of the
+	 * data to be written at the data_ptr pointer. The kernel set this
+	 * value to a negative value to signal an error on a particular query
+	 * item.
+	 */
+	__s32 length;
+
+	/*
+	 * Unused for now.
+	 */
+	__u32 flags;
+
+	/*
+	 * Data will be written at the location pointed by data_ptr when the
+	 * value of length matches the length of the data to be written by the
+	 * kernel.
+	 */
+	__u64 data_ptr;
+};
+
+struct drm_i915_query {
+	__u32 num_items;
+
+	/*
+	 * Unused for now.
+	 */
+	__u32 flags;
+
+	/*
+	 * This point to an array of num_items drm_i915_query_item structures.
+	 */
+	__u64 items_ptr;
+};
+
 #if defined(__cplusplus)
 }
 #endif