openwrt/target/linux/generic/backport-4.9/087-regmap-make-LZO-cache-optional.patch

From de88e9b0354c2e3ff8eae3f97afe43a34f5ed239 Mon Sep 17 00:00:00 2001
From: Jonas Gorski <jonas.gorski@gmail.com>
Date: Sat, 13 May 2017 13:03:21 +0200
Subject: [PATCH] regmap: make LZO cache optional

Commit 2cbbb579bcbe3 ("regmap: Add the LZO cache support") added support
for LZO compression in regcache, but there were never any users added
afterwards. Since LZO support itself has its own size, it currently is
rather a deoptimization.

So make it optional by introducing a symbol that can be selected by
drivers wanting to make use of it.

Saves e.g. ~46 kB on MIPS (size of LZO support + regcache LZO code).

Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
---
I tried using google to find any users (even out-of-tree ones), but at
best I found a single driver submission that was switched to RBTREE in
subsequent resubmissions (MFD_SMSC).

One could maybe also just drop the code because of no users for 5 years,
but that would be up to the maintainer(s) to decide.

 drivers/base/regmap/Kconfig    | 5 ++++-
 drivers/base/regmap/Makefile   | 3 ++-
 drivers/base/regmap/regcache.c | 2 ++
 3 files changed, 8 insertions(+), 2 deletions(-)

--- a/drivers/base/regmap/Kconfig
+++ b/drivers/base/regmap/Kconfig
@@ -4,9 +4,12 @@
 
 config REGMAP
 	default y if (REGMAP_I2C || REGMAP_SPI || REGMAP_SPMI || REGMAP_AC97 || REGMAP_MMIO || REGMAP_IRQ)
+	select IRQ_DOMAIN if REGMAP_IRQ
+	bool
+
+config REGCACHE_COMPRESSED
 	select LZO_COMPRESS
 	select LZO_DECOMPRESS
-	select IRQ_DOMAIN if REGMAP_IRQ
 	bool
 
 config REGMAP_AC97
--- a/drivers/base/regmap/Makefile
+++ b/drivers/base/regmap/Makefile
@@ -2,7 +2,8 @@
 CFLAGS_regmap.o := -I$(src)
 
 obj-$(CONFIG_REGMAP) += regmap.o regcache.o
-obj-$(CONFIG_REGMAP) += regcache-rbtree.o regcache-lzo.o regcache-flat.o
+obj-$(CONFIG_REGMAP) += regcache-rbtree.o regcache-flat.o
+obj-$(CONFIG_REGCACHE_COMPRESSED) += regcache-lzo.o
 obj-$(CONFIG_DEBUG_FS) += regmap-debugfs.o
 obj-$(CONFIG_REGMAP_AC97) += regmap-ac97.o
 obj-$(CONFIG_REGMAP_I2C) += regmap-i2c.o
--- a/drivers/base/regmap/regcache.c
+++ b/drivers/base/regmap/regcache.c
@@ -21,7 +21,9 @@
 
 static const struct regcache_ops *cache_types[] = {
 	&regcache_rbtree_ops,
+#if IS_ENABLED(CONFIG_REGCACHE_COMPRESSED)
 	&regcache_lzo_ops,
+#endif
 	&regcache_flat_ops,
 };