[PATCH 2/3] drm/drm_ras: Extend DRM RAS interface to include telemetry nodes

@@ -16,7 +16,7 @@ definitions:
     type: enum
     name: node-type
     value-start: 1
-    entries: [error-counter]
+    entries: [error-counter, telemetry]
     doc: >-
          Type of the node. Currently, only error-counter nodes are
          supported, which expose reliability counters for a hardware/software

@@ -100,6 +100,31 @@ attribute-sets:
         name: error-value
         type: u32
         doc: Current value of the error counter.
+  -
+    name: telemetry-attrs
+    attributes:
+      -
+        name: node-id
+        type: u32
+        doc: >-
+             Unique identifier for the node.
+             Assigned dynamically by the DRM RAS core upon registration.
+      -
+        name: field
+        type: u32
+        doc:  Telemetry field to be read/written, e.g., SoC temp.
+      -
+        name: value
+        type: u64
+        doc: Value of telemetry field that was read/written.
+      -
+        name: status
+        type: s32
+        doc: Status of the telemetry operation.
+      -
+        name: pad
+        type: pad
+        doc: Alignment padding used for 64-bit
 
 operations:
   list:

@@ -198,6 +223,34 @@ operations:
             - node-id
             - error-id
             - error-threshold
+    -
+      name: telemetry-read
+      doc: Perform a read of the specified telemetry field.
+      attribute-set: telemetry-attrs
+      do:
+        pre: drm-ras-nl-pre-telemetry
+        request:
+          attributes:
+            - node-id
+            - field
+        reply:
+          attributes:
+            - value
+            - status
+    -
+      name: telemetry-write
+      doc: Perform a write of the specified telemetry field.
+      attribute-set: telemetry-attrs
+      do:
+        pre: drm-ras-nl-pre-telemetry
+        request:
+          attributes:
+            - node-id
+            - field
+            - value
+        reply:
+          attributes:
+            - status
 
 mcast-groups:
   list:

@@ -53,6 +53,15 @@
  * 7. SET_ERROR_THRESHOLD: Set error threshold of a given counter.
  *    Userspace must provide Node ID, Error ID and threshold to be set.
  *
+ * 8. TELEMETRY_READ: Read a telemetry value.
+ *    Userspace must provide Node ID and telemetry field to be read.
+ *    Returns the status of the read and the value read (if valid).
+ *
+ * 9. TELEMETRY_WRITE: Write a telemetry value.
+ *    Userspace must provide Node ID, the telemetry field to write, and the value
+ *    to be written.
+ *    Returns the status of the write.
+ *
  * Node registration:
  *
  * - drm_ras_node_register(): Registers a new node and assigns

@@ -63,7 +72,6 @@
  * Node type:
  *
  * - ERROR_COUNTER:
- *     + Currently, only error counters are supported.
  *     + The driver must implement the query_error_counter() callback to provide
  *       the name and the value of the error counter.
  *     + The driver must provide a error_counter_range.last value informing the

@@ -81,6 +89,12 @@
  *       that are raised by the hardware.
  *     + The driver is responsible for error threshold bounds checking.
  *
+ * - TELEMETRY:
+ *     + The driver must implement the telemetry_read() and telemetry_write()
+ *       callbacks.
+ *     + The driver can optionally provide a pre_doit callback, telemetry_pre(),
+ *       to enforce permissions checks on telemetry operations.
+ *
  * Netlink handlers:
  *
  * - drm_ras_nl_list_nodes_dumpit(): Implements the LIST_NODES

@@ -95,6 +109,12 @@
  *   operation, fetching the error threshold of a specific counter.
  * - drm_ras_nl_set_error_threshold_doit(): Implements the SET_ERROR_THRESHOLD doit
  *   operation, setting the error threshold of a specific counter.
+ * - drm_ras_nl_pre_telemetry(): Implements the TELEMETRY_READ and TELEMETRY_WRITE
+ *   pre_doit operation, returning 0 if valid.
+ * - drm_ras_nl_telemetry_read_doit(): Implements the TELEMETRY_READ doit operation,
+ *   invoking the driver's telemetry_read callback and returning the results.
+ * - drm_ras_nl_telemetry_write_doit(): Implements the TELEMETRY_WRITE doit operation,
+ *   invoking the driver's telemetry_write callback and returning the results.
  */
 
 static DEFINE_XARRAY_ALLOC(drm_ras_xa);

@@ -617,6 +637,156 @@ int drm_ras_nl_set_error_threshold_doit(struct sk_buff *skb, struct genl_info *i
 	return set_node_error_threshold(node_id, error_id, threshold);
 }
 
+/**
+ * drm_ras_nl_pre_telemetry - Enforce permission checks
+ * @ops: Generic netlink operations
+ * @skb: Netlink message buffer
+ * @info: Generic Netlink info containing attributes of the request
+ *
+ * Enforces a telemetry node's pre_doit conditions (if they exist).
+ *
+ * Returns 0 if no pre_doit is specified, otherwise returns the pre_doit.
+ */
+int drm_ras_nl_pre_telemetry(const struct genl_split_ops *ops, struct sk_buff *skb,
+			     struct genl_info *info)
+{
+	struct drm_ras_node *node;
+	u32 node_id;
+
+	node_id = nla_get_u32(info->attrs[DRM_RAS_A_TELEMETRY_ATTRS_NODE_ID]);
+	node = xa_load(&drm_ras_xa, node_id);
+
+	if (node->telemetry_pre)
+		return node->telemetry_pre(node);
+
+	return 0;
+}
+
+/**
+ * drm_ras_nl_telemetry_read_doit() - Query a telemetry value
+ * @skb: Netlink message buffer
+ * @info: Generic Netlink info containing attributes of the request
+ *
+ * Extracts the telemetry field from the netlink attributes and
+ * reads that value from the device.
+ *
+ * Return: 0 on success, or negative errno on failure.
+ */
+int drm_ras_nl_telemetry_read_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct drm_ras_node *node;
+	struct sk_buff *msg;
+	struct nlattr *hdr;
+	u32 node_id, field;
+	s32 status;
+	u64 value;
+	int ret;
+
+	if (!info->attrs || !info->attrs[DRM_RAS_A_TELEMETRY_ATTRS_FIELD])
+		return -EINVAL;
+
+	field = nla_get_u32(info->attrs[DRM_RAS_A_TELEMETRY_ATTRS_FIELD]);
+	node_id = nla_get_u32(info->attrs[DRM_RAS_A_TELEMETRY_ATTRS_NODE_ID]);
+
+	node = xa_load(&drm_ras_xa, node_id);
+	if (!node || !node->telemetry_read)
+		return -ENOENT;
+
+	msg = genlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	hdr = genlmsg_iput(msg, info);
+	if (!hdr) {
+		nlmsg_free(msg);
+		return -EMSGSIZE;
+	}
+
+	ret = node->telemetry_read(node, &field, &value, &status);
+	if (ret) {
+		nlmsg_free(msg);
+		return ret;
+	}
+
+	ret = nla_put_s32(msg, DRM_RAS_A_TELEMETRY_ATTRS_STATUS, status);
+	if (ret) {
+		genlmsg_cancel(msg, hdr);
+		nlmsg_free(msg);
+		return ret;
+	}
+
+	ret = nla_put_64bit(msg, DRM_RAS_A_TELEMETRY_ATTRS_VALUE, sizeof(value),
+			    &value, DRM_RAS_A_TELEMETRY_ATTRS_PAD);
+	if (ret) {
+		genlmsg_cancel(msg, hdr);
+		nlmsg_free(msg);
+		return ret;
+	}
+
+	genlmsg_end(msg, hdr);
+
+	return genlmsg_reply(msg, info);
+}
+
+/**
+ * drm_ras_nl_telemetry_write_doit() - Write a telemetry value
+ * @skb: Netlink message buffer
+ * @info: Generic Netlink info containing attributes of the request
+ *
+ * Extracts the telemetry field and value to be written from the netlink
+ * attributes and writes that value to the specified field on the device.
+ *
+ * Return: 0 on success, or negative errno on failure.
+ */
+int drm_ras_nl_telemetry_write_doit(struct sk_buff *skb, struct genl_info *info)
+{
+	struct drm_ras_node *node;
+	struct sk_buff *msg;
+	struct nlattr *hdr;
+	u32 node_id, field;
+	s32 status;
+	u64 value;
+	int ret;
+
+	if (!info->attrs || !info->attrs[DRM_RAS_A_TELEMETRY_ATTRS_FIELD])
+		return -EINVAL;
+
+	value = nla_get_u64(info->attrs[DRM_RAS_A_TELEMETRY_ATTRS_VALUE]);
+	field = nla_get_u32(info->attrs[DRM_RAS_A_TELEMETRY_ATTRS_FIELD]);
+	node_id = nla_get_u32(info->attrs[DRM_RAS_A_TELEMETRY_ATTRS_NODE_ID]);
+
+	node = xa_load(&drm_ras_xa, node_id);
+	if (!node || !node->telemetry_read)
+		return -ENOENT;
+
+	msg = genlmsg_new(NLMSG_GOODSIZE, GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	hdr = genlmsg_iput(msg, info);
+	if (!hdr) {
+		nlmsg_free(msg);
+		return -EMSGSIZE;
+	}
+
+	ret = node->telemetry_write(node, &field, &value, &status);
+	if (ret) {
+		nlmsg_free(msg);
+		return ret;
+	}
+
+	ret = nla_put_s32(msg, DRM_RAS_A_TELEMETRY_ATTRS_STATUS, status);
+	if (ret) {
+		genlmsg_cancel(msg, hdr);
+		nlmsg_free(msg);
+		return ret;
+	}
+
+	genlmsg_end(msg, hdr);
+
+	return genlmsg_reply(msg, info);
+}
+
 /**
  * drm_ras_node_register() - Register a new RAS node
  * @node: Node structure to register

@@ -631,14 +801,21 @@ int drm_ras_node_register(struct drm_ras_node *node)
 	if (!node->device_name || !node->node_name)
 		return -EINVAL;
 
-	/* Currently, only Error Counter Endpoints are supported */
-	if (node->type != DRM_RAS_NODE_TYPE_ERROR_COUNTER)
-		return -EINVAL;
-
-	/* Mandatory entries for Error Counter Node */
-	if (node->type == DRM_RAS_NODE_TYPE_ERROR_COUNTER &&
-	    (!node->error_counter_range.last || !node->query_error_counter))
+	/* Currently, only Error Counter and Telemetry endpoints are supported */
+	switch (node->type) {
+	case DRM_RAS_NODE_TYPE_ERROR_COUNTER:
+		/* Mandatory entries for Error Counter Node */
+		if (!node->error_counter_range.last || !node->query_error_counter)
+			return -EINVAL;
+		break;
+	case DRM_RAS_NODE_TYPE_TELEMETRY:
+		/* Mandatory entries for Telemetry Node */
+		if (!node->telemetry_read || !node->telemetry_write)
+			return -EINVAL;
+		break;
+	default:
 		return -EINVAL;
+	}
 
 	return xa_alloc(&drm_ras_xa, &node->id, node, xa_limit_32b, GFP_KERNEL);
 }

@@ -41,6 +41,19 @@ static const struct nla_policy drm_ras_set_error_threshold_nl_policy[DRM_RAS_A_E
 	[DRM_RAS_A_ERROR_COUNTER_ATTRS_ERROR_THRESHOLD] = { .type = NLA_U32, },
 };
 
+/* DRM_RAS_CMD_TELEMETRY_READ - do */
+static const struct nla_policy drm_ras_telemetry_read_nl_policy[DRM_RAS_A_TELEMETRY_ATTRS_FIELD + 1] = {
+	[DRM_RAS_A_TELEMETRY_ATTRS_NODE_ID] = { .type = NLA_U32, },
+	[DRM_RAS_A_TELEMETRY_ATTRS_FIELD] = { .type = NLA_U32, },
+};
+
+/* DRM_RAS_CMD_TELEMETRY_WRITE - do */
+static const struct nla_policy drm_ras_telemetry_write_nl_policy[DRM_RAS_A_TELEMETRY_ATTRS_VALUE + 1] = {
+	[DRM_RAS_A_TELEMETRY_ATTRS_NODE_ID] = { .type = NLA_U32, },
+	[DRM_RAS_A_TELEMETRY_ATTRS_FIELD] = { .type = NLA_U32, },
+	[DRM_RAS_A_TELEMETRY_ATTRS_VALUE] = { .type = NLA_U64, },
+};
+
 /* Ops table for drm_ras */
 static const struct genl_split_ops drm_ras_nl_ops[] = {
 	{

@@ -83,6 +96,22 @@ static const struct genl_split_ops drm_ras_nl_ops[] = {
 		.maxattr	= DRM_RAS_A_ERROR_COUNTER_ATTRS_ERROR_THRESHOLD,
 		.flags		= GENL_ADMIN_PERM | GENL_CMD_CAP_DO,
 	},
+	{
+		.cmd		= DRM_RAS_CMD_TELEMETRY_READ,
+		.pre_doit	= drm_ras_nl_pre_telemetry,
+		.doit		= drm_ras_nl_telemetry_read_doit,
+		.policy		= drm_ras_telemetry_read_nl_policy,
+		.maxattr	= DRM_RAS_A_TELEMETRY_ATTRS_FIELD,
+		.flags		= GENL_CMD_CAP_DO,
+	},
+	{
+		.cmd		= DRM_RAS_CMD_TELEMETRY_WRITE,
+		.pre_doit	= drm_ras_nl_pre_telemetry,
+		.doit		= drm_ras_nl_telemetry_write_doit,
+		.policy		= drm_ras_telemetry_write_nl_policy,
+		.maxattr	= DRM_RAS_A_TELEMETRY_ATTRS_VALUE,
+		.flags		= GENL_CMD_CAP_DO,
+	},
 };
 
 static const struct genl_multicast_group drm_ras_nl_mcgrps[] = {

@@ -12,6 +12,9 @@
 
 #include <uapi/drm/drm_ras.h>
 
+int drm_ras_nl_pre_telemetry(const struct genl_split_ops *ops,
+			     struct sk_buff *skb, struct genl_info *info);
+
 int drm_ras_nl_list_nodes_dumpit(struct sk_buff *skb,
 				 struct netlink_callback *cb);
 int drm_ras_nl_get_error_counter_doit(struct sk_buff *skb,

@@ -24,6 +27,9 @@ int drm_ras_nl_get_error_threshold_doit(struct sk_buff *skb,
 					struct genl_info *info);
 int drm_ras_nl_set_error_threshold_doit(struct sk_buff *skb,
 					struct genl_info *info);
+int drm_ras_nl_telemetry_read_doit(struct sk_buff *skb, struct genl_info *info);
+int drm_ras_nl_telemetry_write_doit(struct sk_buff *skb,
+				    struct genl_info *info);
 
 enum {
 	DRM_RAS_NLGRP_ERROR_REPORT,

@@ -100,6 +100,45 @@ struct drm_ras_node {
 	 */
 	int (*set_error_threshold)(struct drm_ras_node *node, u32 error_id, u32 threshold);
 
+	/**
+	 * @telemetry_pre:
+	 *
+	 * This callback is used to enforce any pre_doit conditions necessary
+	 * for telemetry. This is an optional callback for telemetry_node.
+	 *
+	 * Returns 0 on success, negative error code on failure.
+	 */
+	int (*telemetry_pre)(struct drm_ras_node *ep);
+
+	/**
+	 * @telemetry_read:
+	 *
+	 * This callback is used for a drm-ras telemetry node to read a
+	 * telemetry value. This is a mandatory callback for telemetry_node.
+	 *
+	 * The callback will read the desired device-specific field into value
+	 * and update status corresponding to a device-specific error code.
+	 *
+	 * Returns 0 on success, negative error code on failure.
+	 */
+	int (*telemetry_read)(struct drm_ras_node *ep, u32 *field, u64 *value,
+			      s32 *status);
+
+	/**
+	 * @telemetry_write:
+	 *
+	 * This callback is used for a drm-ras telemetry node to write a
+	 * telemetry value. This is a mandatory callback for telemetry_node.
+	 *
+	 * The callback will write the value to the desired device-specific
+	 * field and update status corresponding to a device-specific error
+	 * code.
+	 *
+	 * Returns 0 on success, negative error code on failure.
+	 */
+	int (*telemetry_write)(struct drm_ras_node *ep, u32 *field, u64 *value,
+			       s32 *status);
+
 	/** @priv: Driver private data */
 	void *priv;
 };

@@ -16,6 +16,7 @@
  */
 enum drm_ras_node_type {
 	DRM_RAS_NODE_TYPE_ERROR_COUNTER = 1,
+	DRM_RAS_NODE_TYPE_TELEMETRY,
 };
 
 enum {

@@ -51,6 +52,17 @@ enum {
 	DRM_RAS_A_ERROR_EVENT_ATTRS_MAX = (__DRM_RAS_A_ERROR_EVENT_ATTRS_MAX - 1)
 };
 
+enum {
+	DRM_RAS_A_TELEMETRY_ATTRS_NODE_ID = 1,
+	DRM_RAS_A_TELEMETRY_ATTRS_FIELD,
+	DRM_RAS_A_TELEMETRY_ATTRS_VALUE,
+	DRM_RAS_A_TELEMETRY_ATTRS_STATUS,
+	DRM_RAS_A_TELEMETRY_ATTRS_PAD,
+
+	__DRM_RAS_A_TELEMETRY_ATTRS_MAX,
+	DRM_RAS_A_TELEMETRY_ATTRS_MAX = (__DRM_RAS_A_TELEMETRY_ATTRS_MAX - 1)
+};
+
 enum {
 	DRM_RAS_CMD_LIST_NODES = 1,
 	DRM_RAS_CMD_GET_ERROR_COUNTER,

@@ -58,6 +70,8 @@ enum {
 	DRM_RAS_CMD_ERROR_EVENT,
 	DRM_RAS_CMD_GET_ERROR_THRESHOLD,
 	DRM_RAS_CMD_SET_ERROR_THRESHOLD,
+	DRM_RAS_CMD_TELEMETRY_READ,
+	DRM_RAS_CMD_TELEMETRY_WRITE,
 
 	__DRM_RAS_CMD_MAX,
 	DRM_RAS_CMD_MAX = (__DRM_RAS_CMD_MAX - 1)