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This version (08 Nov 2011 17:40) was approved by mhennerich.The Previously approved version (08 Nov 2011 17:35) is available.Diff

ADP1650 LED Flash Linux Driver

Supported Devices

Evaluation Boards

Description

Couldn't find description in http://www.analog.com/ADP1650

Source Code

Status

Source Mainlined?
git In Progress

Files

Example platform device initialization

For compile time configuration, it’s common Linux practice to keep board- and application-specific configuration out of the main driver file, instead putting it into the board support file.

For devices on custom boards, as typical of embedded and SoC-(system-on-chip) based hardware, Linux uses platform_data to point to board-specific structures describing devices and how they are connected to the SoC. This can include available ports, chip variants, preferred modes, default initialization, additional pin roles, and so on. This shrinks the board-support packages (BSPs) and minimizes board and application specific #ifdefs in drivers.

21 Oct 2010 16:10 · Michael Hennerich

platform_data: Platform data specific to the ADP1650 device.
Includes feature selections and default initialization.

Please see include/linux/i2c/adp1650.h for details.

#include <linux/i2c/adp1650.h>
 
static struct adp1650_leds_platform_data adp1650_pdata = {
	.timer_iocfg = 	ADP1650_IOCFG_IO2_HIGH_IMP |
			ADP1650_IOCFG_IO1_TORCH |
			ADP1650_FL_TIMER_ms(500),
 
	.current_set = 	ADP1650_I_FL_mA(900) |
			ADP1650_I_TOR_mA(100),
 
	.output_mode = 	ADP1650_IL_PEAK_2A25 |
			ADP1650_STR_LV_EDGE |
			ADP1650_FREQ_FB_EN |
			ADP1650_OUTPUT_EN |
			ADP1650_STR_MODE_HW |
			ADP1650_STR_MODE_STBY,
 
	.control = 	ADP1650_I_TX2_mA(400) |
			ADP1650_I_TX1_mA(400),
 
	.ad_mode =	ADP1650_DYN_OVP_EN |
			ADP1650_STR_POL_ACTIVE_HIGH |
			ADP1650_I_ILED_2mA75 |
			ADP1650_IL_DC_1A50 |
			ADP1650_IL_DC_EN,
 
	.batt_low =	ADP1650_CL_SOFT_EN |
			ADP1650_I_VB_LO_mA(400) |
			ADP1650_V_VB_LO_3V50,
 
	.gpio_enable = -1,
};

Declaring I2C devices

Unlike PCI or USB devices, I2C devices are not enumerated at the hardware level. Instead, the software must know which devices are connected on each I2C bus segment, and what address these devices are using. For this reason, the kernel code must instantiate I2C devices explicitly. There are different ways to achieve this, depending on the context and requirements. However the most common method is to declare the I2C devices by bus number.

This method is appropriate when the I2C bus is a system bus, as in many embedded systems, wherein each I2C bus has a number which is known in advance. It is thus possible to pre-declare the I2C devices that inhabit this bus. This is done with an array of struct i2c_board_info, which is registered by calling i2c_register_board_info().

So, to enable such a driver one need only edit the board support file by adding an appropriate entry to i2c_board_info.

For more information see: Documentation/i2c/instantiating-devices

21 Oct 2010 16:10 · Michael Hennerich
static struct i2c_board_info __initdata board_i2c_board_info[] = {
#if defined(CONFIG_LEDS_ADP1650) || defined(CONFIG_LEDS_ADP1650_MODULE)
	{
		I2C_BOARD_INFO("adp1650", 0x30),
		.platform_data = (void *)&adp1650_pdata,
	},
#endif
};
static int __init board_init(void)
{
	[--snip--]
 
	i2c_register_board_info(0, board_i2c_board_info,
				ARRAY_SIZE(board_i2c_board_info));
	[--snip--]
 
	return 0;
}
arch_initcall(board_init);

Adding Linux driver support

Configure kernel with “make menuconfig” (alternatively use “make xconfig” or “make qconfig”)

The ADP1650 LED driver depends on I2C.

Device Drivers  --->
	[*] LED Support  ---> 
		--- LED Support
		[*]   LED Class Support
			* LED drivers *

		<--snip-->
		<*>   LED Support for ADP1650 I2C chips
		<--snip-->

Driver testing

LED handling under Linux

The LED class allows control of LEDs from userspace. LEDs appear in /sys/class/leds/. The brightness file will set the brightness of the LED (taking a value 0-255).

For more information read linux/Documentaion/leds-class.txt

brightness
get/set LED brightness (an integer between 0 and 255)
max_brightness
the maximum brightness value.

Driver specific brightness interpretation

Value Define Description Intensity
0 FL_MODE_OFF Turns LED/FLASH off 0
1 FL_MODE_TORCH_25mA Software initiated TORCH/Assist light 25mA
2 FL_MODE_TORCH_50mA (STROBE) triggers FLASH 50mA
3 FL_MODE_TORCH_75mA 75mA
4 FL_MODE_TORCH_100mA 100mA
5 FL_MODE_TORCH_125mA 125mA
6 FL_MODE_TORCH_150mA 150mA
7 FL_MODE_TORCH_175mA 175mA
8 FL_MODE_TORCH_200mA 200mA
9 FL_MODE_TORCH_TRIG_EXT_25mA Hardware (GPIO1) triggered TORCH/Assist light 25mA
10 FL_MODE_TORCH_TRIG_EXT_50mA (STROBE) triggers FLASH 50mA
11 FL_MODE_TORCH_TRIG_EXT_75mA 75mA
12 FL_MODE_TORCH_TRIG_EXT_100mA 100mA
13 FL_MODE_TORCH_TRIG_EXT_125mA 125mA
14 FL_MODE_TORCH_TRIG_EXT_150mA 150mA
15 FL_MODE_TORCH_TRIG_EXT_175mA 175mA
16 FL_MODE_TORCH_TRIG_EXT_200mA 200mA
254 FL_MODE_FLASH Software initiated LED FLASH I_FL
255 FL_MODE_FLASH_TRIG_EXT Hardware (STROBE) triggered LED FLASH I_FL

Example LED usage

root:/> cd sys/class/leds/adp1650/

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-0/0-0030/leds/adp1650> ls -l
-rw-r--r--    1 root     root          4096 Jan  5 08:42 brightness
lrwxrwxrwx    1 root     root             0 Jan  5 08:23 device -> ../../../0-0030
-r--r--r--    1 root     root          4096 Jan  5 08:23 max_brightness
drwxr-xr-x    2 root     root             0 Jan  5 08:23 power
lrwxrwxrwx    1 root     root             0 Jan  5 08:23 subsystem -> ../../../../../../../class/leds
-rw-r--r--    1 root     root          4096 Jan  5 08:23 uevent

Enable TORCH/Assist Light (Intensity 100mA)

A subsequent assert of STROBE will trigger the FLASH

This specifies any shell prompt running on the target

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-0/0-0030/leds/adp1650> echo 4 > brightness

Prepare TORCH/Assist Light for an GPIO1 enable trigger (Intensity 100mA)

A subsequent assert of STROBE will trigger the FLASH

This specifies any shell prompt running on the target

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-0/0-0030/leds/adp1650> echo 12 > brightness

Initiate FLASH (Intensity set by I_FL)

This specifies any shell prompt running on the target

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-0/0-0030/leds/adp1650> echo 254 > brightness

Prepare FLASH for an STROBE triggered enable (Intensity set by I_FL)

This specifies any shell prompt running on the target

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-0/0-0030/leds/adp1650> echo 255 > brightness

Disable all LED activity

This specifies any shell prompt running on the target

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-0/0-0030/leds/adp1650> echo 0 > brightness

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