[PATCH v9 5/6] drm/i915: add query uAPI

[Lionel Landwerlin <lionel.g.landwerlin@intel.com>]

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)

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/i915/Makefile     |  1 +
 drivers/gpu/drm/i915/i915_drv.c   |  1 +
 drivers/gpu/drm/i915/i915_drv.h   |  3 ++
 drivers/gpu/drm/i915/i915_query.c | 67 +++++++++++++++++++++++++++++++++++++++
 include/uapi/drm/i915_drm.h       | 37 +++++++++++++++++++++
 5 files changed, 109 insertions(+)
 create mode 100644 drivers/gpu/drm/i915/i915_query.c

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 3bddd8a06806..b0415a3e2d59 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -69,6 +69,7 @@ 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 a4cf6858e39c..e7098cf07ef5 100644
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -2826,6 +2826,7 @@ 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_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 317953484fec..b7ca9588b993 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3622,6 +3622,9 @@ extern void i915_perf_fini(struct drm_i915_private *dev_priv);
 extern void i915_perf_register(struct drm_i915_private *dev_priv);
 extern void i915_perf_unregister(struct drm_i915_private *dev_priv);
 
+/* i915_query.c */
+int i915_query_ioctl(struct drm_device *dev, void *data, struct drm_file *file);
+
 /* i915_suspend.c */
 extern int i915_save_state(struct drm_i915_private *dev_priv);
 extern int i915_restore_state(struct drm_i915_private *dev_priv);
diff --git a/drivers/gpu/drm/i915/i915_query.c b/drivers/gpu/drm/i915/i915_query.c
new file mode 100644
index 000000000000..5aa886313cf9
--- /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))
+			return -EINVAL;
+
+		ret = i915_query_funcs[func_idx](dev_priv, &item);
+
+		/* 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/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 536ee4febd74..d94a00380bf6 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.
@@ -1613,6 +1615,41 @@ 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
-- 
2.15.1

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