include: Move ascii85 functions from i915 to linux/ascii85.h

The i915 DRM driver very cleverly used ascii85 encoding for their
GPU state file. Move the encode functions to a general header file to
support other drivers that might be interested in the same
functionality.

v4: Make the return value const char * as suggested by Chris Wilson
v3: Fix error_puts -> err_puts pointed out by the 01.org bot
v2: Update API to be cleaner for the caller as suggested by Chris Wilson

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>

1 files changed, 38 insertions, 0 deletions

diff --git a/include/linux/ascii85.h b/include/linux/ascii85.h
new file mode 100644
index 000000000000..4cc40201273e
--- /dev/null
+++ b/include/linux/ascii85.h
@@ -0,0 +1,38 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (c) 2008 Intel Corporation
+ * Copyright (c) 2018 The Linux Foundation. All rights reserved.
+ */
+
+#ifndef _ASCII85_H_
+#define _ASCII85_H_
+
+#include <linux/kernel.h>
+
+#define ASCII85_BUFSZ 6
+
+static inline long
+ascii85_encode_len(long len)
+{
+        return DIV_ROUND_UP(len, 4);
+}
+
+static inline const char *
+ascii85_encode(u32 in, char *out)
+{
+        int i;
+
+        if (in == 0)
+                return "z";
+
+        out[5] = '\0';
+        for (i = 5; i--; ) {
+                out[i] = '!' + in % 85;
+                in /= 85;
+        }
+
+        return out;
+}
+
+#endif