[U-Boot] [PATCH 09/14] dm: Hwmon UDM subsystem analysis added.

Marek Vasut
2012-08-08T11:42:25Z

From: Tomas Hlavacek <tmshlvck@gmail.com>

Signed-off-by: Tomas Hlavacek <tmshlvck@gmail.com>
---
doc/driver-model/UDM-hwmon.txt | 119 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 119 insertions(+)
create mode 100644 doc/driver-model/UDM-hwmon.txt

diff --git a/doc/driver-model/UDM-hwmon.txt b/doc/driver-model/UDM-hwmon.txt
new file mode 100644
index 0000000..97444c0
--- /dev/null
+++ b/doc/driver-model/UDM-hwmon.txt
@@ -0,0 +1,119 @@
+The U-Boot Driver Model Project
+===============================
+Hwmon device subsystem analysis
+===============================
+
+Tomas Hlavacek <tmshlvck@gmail.com>
+2012-03-02
+
+I) Overview
+-----------
+
+U-Boot currently implements one API for HW monitoring devices. The
+interface is defined in include/dtt.h and comprises of functions:
+
+ void dtt_init(void);
+ int dtt_init_one(int);
+ int dtt_read(int sensor, int reg);
+ int dtt_write(int sensor, int reg, int val);
+ int dtt_get_temp(int sensor);
+
+The functions are implemented by a proper device driver in drivers/hwmon
+directory and the driver to be compiled in is selected in a Makefile.
+Drivers are mutually exclusive.
+
+Drivers depends on I2O code and naturally on board specific data. There are
+few ad-hoc constants put in dtt.h file and driver headers and code. This
+has to be consolidated into board specific data or driver headers if those
+constants makes sense globally.
+
+
+II) Approach
+------------
+
+ 1) New API
+ ----------
+ In the UDM each hwmon driver would register itself by a function
+
+ int hwmon_device_register(struct instance *i,
+ struct hwmon_device_ops *o);
+
+ The structure being defined as follows:
+
+ struct hwmon_device_ops {
+ int (*read)(struct instance *i, int sensor, int reg);
+ int (*write)(struct instance *i, int sensor, int reg,
+ int val);
+ int (*get_temp)(struct instance *i, int sensor);
+ };
+
+
+ 2) Conversion thougths
+ ----------------------
+ U-Boot hwmon drivers exports virtually the same functions (with exceptions)
+ and we are considering low number of drivers and code anyway. The interface
+ is already similar and unified by the interface defined in dtt.h.
+ Current initialization functions dtt_init() and dtt_init_one() will be
+ converted into probe() and hwmon_device_register(), so the funcionality will
+ be kept in more proper places. Besides implementing core registration and
+ initialization we need to do code cleanup, especially separate
+ driver-specific and HW specific constants.
+
+ 3) Special consideration due to early initialization
+ ----------------------------------------------------
+ The dtt_init() function call is used during early initialization in
+ board/gdsys/405ex/io64.c for starting up fans. The dtt code is perfectly
+ usable in the early stage because it uses only local variables and no heap
+ memory is required at this level. However the underlying code of I2C has to
+ keep the same properties with regard to possibility of running in early
+ initialization stage.
+
+III) Analysis of in-tree drivers
+--------------------------------
+
+ 1) drivers/hwmon/lm81.c
+ -----------------------
+ The driver is standard dtt. Simple conversion is possible.
+
+
+ 2) drivers/hwmon/ds1722.c
+ -------------------------
+ The driver is not standard dtt, but interface is similar to dtt.
+ The interface has to be changed in order to comply to above mentioned
+ specification.
+
+
+ 3) drivers/hwmon/ds1775.c
+ -------------------------
+ The driver is standard dtt. Simple conversion is possible.
+
+
+ 4) drivers/hwmon/lm73.c
+ -----------------------
+ The driver is standard dtt. Simple conversion is possible.
+
+
+ 5) drivers/hwmon/lm63.c
+ -----------------------
+ The driver is standard dtt. Simple conversion is possible.
+
+
+ 6) drivers/hwmon/adt7460.c
+ --------------------------
+ The driver is standard dtt. Simple conversion is possible.
+
+
+ 7) drivers/hwmon/lm75.c
+ -----------------------
+ The driver is standard dtt. Simple conversion is possible.
+
+
+ 8) drivers/hwmon/ds1621.c
+ -------------------------
+ The driver is standard dtt. Simple conversion is possible.
+
+
+ 9) drivers/hwmon/adm1021.c
+ --------------------------
+ The driver is standard dtt. Simple conversion is possible.
+
--
1.7.10.4