merged to 5.6.6

Author: dettus

sys/external/bsd/drm2/dist/drm/i915/i915_perf.c

@@ -2999,60 +2999,6 @@ void i915_oa_init_reg_state(const struct intel_context *ce,
 		gen8_update_reg_state_unlocked(ce, stream);
 }
 
-/**
- * i915_perf_read_locked - &i915_perf_stream_ops->read with error normalisation
- * @stream: An i915 perf stream
- * @file: An i915 perf stream file
- * @buf: destination buffer given by userspace
- * @count: the number of bytes userspace wants to read
- * @ppos: (inout) file seek position (unused)
- *
- * Besides wrapping &i915_perf_stream_ops->read this provides a common place to
- * ensure that if we've successfully copied any data then reporting that takes
- * precedence over any internal error status, so the data isn't lost.
- *
- * For example ret will be -ENOSPC whenever there is more buffered data than
- * can be copied to userspace, but that's only interesting if we weren't able
- * to copy some data because it implies the userspace buffer is too small to
- * receive a single record (and we never split records).
- *
- * Another case with ret == -EFAULT is more of a grey area since it would seem
- * like bad form for userspace to ask us to overrun its buffer, but the user
- * knows best:
- *
- *   http://yarchive.net/comp/linux/partial_reads_writes.html
- *
- * Returns: The number of bytes copied or a negative error code on failure.
- */
-#ifdef __NetBSD__
-static int i915_perf_read_locked(struct i915_perf_stream *stream,
-				     struct file *file,
-				     struct uio *buf,
-				     kauth_cred_t count, /* XXX dummy */
-				     int ppos)		 /* XXX dummy */
-{
-	return stream->ops->read(stream, buf, count, ppos);
-}
-#else
-static ssize_t i915_perf_read_locked(struct i915_perf_stream *stream,
-				     struct file *file,
-				     char __user *buf,
-				     size_t count,
-				     loff_t *ppos)
-{
-	/* Note we keep the offset (aka bytes read) separate from any
-	 * error status so that the final check for whether we return
-	 * the bytes read with a higher precedence than any error (see
-	 * comment below) doesn't need to be handled/duplicated in
-	 * stream->ops->read() implementations.
-	 */
-	size_t offset = 0;
-	int ret = stream->ops->read(stream, buf, count, &offset);
-
-	return offset ?: (ret ?: -EAGAIN);
-}
-#endif
-
 /**
  * i915_perf_read - handles read() FOP for i915 perf stream FDs
  * @file: An i915 perf stream file
@@ -3090,7 +3036,7 @@ static ssize_t i915_perf_read(struct file *file,
 	struct i915_perf_stream *stream = file->private_data;
 #endif
 	struct i915_perf *perf = stream->perf;
-	ssize_t ret;
+	size_t offset = 0;
 
 	/* To ensure it's handled consistently we simply treat all reads of a
 	 * disabled stream as an error. In particular it might otherwise lead
@@ -3119,13 +3065,12 @@ static ssize_t i915_perf_read(struct file *file,
 				return ret;
 
 			mutex_lock(&perf->lock);
-			ret = i915_perf_read_locked(stream, file,
-						    buf, count, ppos);
+			ret = stream->ops->read(stream, buf, count, &offset);
 			mutex_unlock(&perf->lock);
-		} while (ret == -EAGAIN);
+		} while (!offset && !ret);
 	} else {
 		mutex_lock(&perf->lock);
-		ret = i915_perf_read_locked(stream, file, buf, count, ppos);
+		ret = stream->ops->read(stream, buf, count, &offset);
 		mutex_unlock(&perf->lock);
 	}
 
@@ -3136,15 +3081,15 @@ static ssize_t i915_perf_read(struct file *file,
 	 * and read() returning -EAGAIN. Clearing the oa.pollin state here
 	 * effectively ensures we back off until the next hrtimer callback
 	 * before reporting another EPOLLIN event.
+	 * The exception to this is if ops->read() returned -ENOSPC which means
+	 * that more OA data is available than could fit in the user provided
+	 * buffer. In this case we want the next poll() call to not block.
 	 */
-	if (ret >= 0 || ret == -EAGAIN) {
-		/* Maybe make ->pollin per-stream state if we support multiple
-		 * concurrent streams in the future.
-		 */
+	if (ret != -ENOSPC)
 		stream->pollin = false;
-	}
 
-	return ret;
+	/* Possible values for ret are 0, -EFAULT, -ENOSPC, -EIO, ... */
+	return offset ?: (ret ?: -EAGAIN);
 }
 
 static enum hrtimer_restart oa_poll_check_timer_cb(struct hrtimer *hrtimer)