mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-12-02 01:19:49 +00:00
118 lines
3.7 KiB
Text
118 lines
3.7 KiB
Text
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.
|