[PATCH 0/4] regmap: Generic I2C and SPI register map library

July 15th, 2011 - 02:30 am ET by Mark Brown | Report spam

This is a version of a series I've been posting for most of this release
cycle which abstracts out a bunch of widely duplicated code for doing
register I/O on devices with control slow buses like I2C and SPI. As
well as saving us code for the register I/O itself this should also make
it easier to factor out further higher level code for this class of
devices.

The main change in this version of the series is that I've moved the
bus-specific files into the relevant drivers/ directories. Hopefully
Jean, Ben and Grant will be OK with this and with some churn in this
code from the regmap tree that may be created as we build out the core
API and possibly refactor the interface to the bus code.

I realise it's a bit late in the cycle but it'd be really good if we
could get this merged in the next merge window, or accepted for about
then so we can create a stable branch we can merge into subsystem trees
in order to get drivers using this merged for 3.2. As there's only one
user included the series it should be pretty low risk.

The code is in a subdirectory because I'm anticipating it'll grow quite
a bit as we add facilities like fancy cache mechanisms on top of it.

A more verbose cover letter:

Many I2C and SPI based devices implement register maps on top of the raw
wire interface. This is generally done in a very standard fashion by
devices, resulting in a lot of very similar code in drivers. For some
time now ASoC has factored this code out into the subsystem but that's
only useful for audio devices. The intention with this series is to
generalise the concept so that it can be used throughout the kernel.

It's not intended that this be suitable for all devices - some devices
have things that are hard to generalise like registers with variable
size and paging which are hard to support genericly. At the minute the
code is focused on the common cases. It is likely that the same code
could be used with other buses with similar properties to I2C and SPI.

Currently only physical I/O is handled, the intention is that once this
support has been reviewed and merged the generic register cache code
that ASoC includes will also be factored out too, along with logging and
diagnostic infrastructure for register maps. For devices with read
heavy workloads (especially those that need a lot of read/modify/write
cycles) or which don't support read at all this can provide a useful
performance improvement and for sparse register maps there's a lot of
benefit in relatively complex cache code.

I'm not entirely happy with the implementation currently but am fairly
happy with the external interfaces.

A bunch more drivers have been converted to use this framework,
including the existing ASoC register I/O code, but due to various -next
dependencies these don't apply easily so I've omitted them from this
posting of the series - you can see them in the mailing list archives,
they've not been updated during the review.

There's a git branch at:

git://git.kernel.org/pub/scm/linux/...regmap.git for-next

I've also created a regmap-asoc branch there which merges current ASoC
code with the regmap code.

The following changes since commit 620917de59eeb934b9f8cf35cc2d95c1ac8ed0fc:

Linux 3.0-rc7 (2011-07-11 16:51:52 -0700)

are available in the git repository at:
git://git.kernel.org/pub/scm/linux/...regmap.git for-next

Mark Brown (4):
regmap: Add generic non-memory mapped register access API
regmap: Add I2C bus support
regmap: Add SPI bus support
regulator: Convert tps65023 to use regmap API

MAINTAINERS | 7 +
drivers/base/Kconfig | 2 +
drivers/base/Makefile | 1 +
drivers/base/regmap/Kconfig | 6 +
drivers/base/regmap/Makefile | 1 +
drivers/base/regmap/regmap.c | 481 ++++++++++++++++++++++++++++++++
drivers/i2c/Kconfig | 4 +
drivers/i2c/Makefile | 1 +
drivers/i2c/i2c-regmap.c | 111 ++++++++
drivers/regulator/Kconfig | 1 +
drivers/regulator/tps65023-regulator.c | 98 ++--
drivers/spi/Kconfig | 4 +
drivers/spi/Makefile | 1 +
drivers/spi/spi-regmap.c | 76 +++++
include/linux/regmap.h | 76 +++++
15 files changed, 799 insertions(+), 71 deletions(-)
create mode 100644 drivers/base/regmap/Kconfig
create mode 100644 drivers/base/regmap/Makefile
create mode 100644 drivers/base/regmap/regmap.c
create mode 100644 drivers/i2c/i2c-regmap.c
create mode 100644 drivers/spi/spi-regmap.c
create mode 100644 include/linux/regmap.h
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#1 Mark Brown

July 15th, 2011 - 02:30 am ET | Report spam

We initialise at postcore_initcall() so that we are available before users
- some users such as PMICs initialise very early. We won't actually try to
use any of the bus until a device initialises a register map.

Signed-off-by: Mark Brown
Acked-by: Liam Girdwood
Acked-by: Wolfram Sang

drivers/base/regmap/Makefile | 1 -
drivers/i2c/Kconfig | 4 ++
drivers/i2c/Makefile | 1 +
drivers/i2c/i2c-regmap.c | 111 ++++++++++++++++++++++++++++++++++++++++++
4 files changed, 116 insertions(+), 1 deletions(-)
create mode 100644 drivers/i2c/i2c-regmap.c

diff --git a/drivers/base/regmap/Makefile b/drivers/base/regmap/Makefile
index 1e5037e..7532e13 100644
a/drivers/base/regmap/Makefile
+++ b/drivers/base/regmap/Makefile
@@ -1,2 +1 @@
obj-$(CONFIG_REGMAP) += regmap.o
-
diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index 30f06e9..cba758b 100644
a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -6,6 +6,7 @@ menuconfig I2C
tristate "I2C support"
depends on HAS_IOMEM
select RT_MUTEXES
+ select I2C_REGMAP if REGMAP
help
I2C (pronounce: I-square-C) is a slow serial bus protocol used in
many micro controller applications and developed by Philips. SMBus,
@@ -110,4 +111,7 @@ config I2C_DEBUG_BUS
a problem with I2C support and want to see more of what is going
on.

+config I2C_REGMAP
+ tristate
+
endif # I2C
diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index beee6b2..85d6699 100644
a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -7,6 +7,7 @@ obj-$(CONFIG_I2C) += i2c-core.o
obj-$(CONFIG_I2C_SMBUS) += i2c-smbus.o
obj-$(CONFIG_I2C_CHARDEV) += i2c-dev.o
obj-$(CONFIG_I2C_MUX) += i2c-mux.o
+obj-$(CONFIG_I2C_REGMAP) += i2c-regmap.o
obj-y += algos/ busses/ muxes/

ccflags-$(CONFIG_I2C_DEBUG_CORE) := -DDEBUG
diff --git a/drivers/i2c/i2c-regmap.c b/drivers/i2c/i2c-regmap.c
new file mode 100644
index 0000000..6a60eb3
/dev/null
+++ b/drivers/i2c/i2c-regmap.c
@@ -0,0 +1,111 @@
+/*
+ * Register map access API - I2C support
+ *
+ * Copyright 2011 Wolfson Microelectronics plc
+ *
+ * Author: Mark Brown
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/regmap.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/init.h>
+
+static int regmap_i2c_write(struct device *dev, const void *data, size_t count)
+{
+ struct i2c_client *i2c = to_i2c_client(dev);
+ int ret;
+
+ ret = i2c_master_send(i2c, data, count);
+ if (ret == count)
+ return 0;
+ else if (ret < 0)
+ return ret;
+ else
+ return -EIO;
+}
+
+static int regmap_i2c_gather_write(struct device *dev,
+ const void *reg, size_t reg_size,
+ const void *val, size_t val_size)
+{
+ struct i2c_client *i2c = to_i2c_client(dev);
+ struct i2c_msg xfer[2];
+ int ret;
+
+ /* If the I2C controller can't do a gather tell the core, it
+ * will substitute in a linear write for us.
+ */
+ if (!i2c_check_functionality(i2c->adapter, I2C_FUNC_PROTOCOL_MANGLING))
+ return -ENOTSUPP;
+
+ xfer[0].addr = i2c->addr;
+ xfer[0].flags = 0;
+ xfer[0].len = reg_size;
+ xfer[0].buf = (void *)reg;
+
+ xfer[1].addr = i2c->addr;
+ xfer[1].flags = I2C_M_NOSTART;
+ xfer[1].len = val_size;
+ xfer[1].buf = (void *)val;
+
+ ret = i2c_transfer(i2c->adapter, xfer, 2);
+ if (ret == 2)
+ return 0;
+ if (ret < 0)
+ return ret;
+ else
+ return -EIO;
+}
+
+static int regmap_i2c_read(struct device *dev,
+ const void *reg, size_t reg_size,
+ void *val, size_t val_size)
+{
+ struct i2c_client *i2c = to_i2c_client(dev);
+ struct i2c_msg xfer[2];
+ int ret;
+
+ xfer[0].addr = i2c->addr;
+ xfer[0].flags = 0;
+ xfer[0].len = reg_size;
+ xfer[0].buf = (void *)reg;
+
+ xfer[1].addr = i2c->addr;
+ xfer[1].flags = I2C_M_RD;
+ xfer[1].len = val_size;
+ xfer[1].buf = val;
+
+ ret = i2c_transfer(i2c->adapter, xfer, 2);
+ if (ret == 2)
+ return 0;
+ else if (ret < 0)
+ return ret;
+ else
+ return -EIO;
+}
+
+static struct regmap_bus regmap_i2c = {
+ .type = &i2c_bus_type,
+ .write = regmap_i2c_write,
+ .gather_write = regmap_i2c_gather_write,
+ .read = regmap_i2c_read,
+ .owner = THIS_MODULE,
+};
+
+static int __init regmap_i2c_init(void)
+{
+ regmap_add_bus(&regmap_i2c);
+ return 0;
+}
+postcore_initcall(regmap_i2c_init);
+
+static void __exit regmap_i2c_exit(void)
+{
+ regmap_del_bus(&regmap_i2c);
+}
+module_exit(regmap_i2c_exit);
1.7.5.4

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[PATCH 0/4] regmap: Generic I2C and SPI register map library

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