diff options
Diffstat (limited to 'Documentation/i2c/instantiating-devices')
| -rw-r--r-- | Documentation/i2c/instantiating-devices | 49 |
1 files changed, 43 insertions, 6 deletions
diff --git a/Documentation/i2c/instantiating-devices b/Documentation/i2c/instantiating-devices index 87da405a859..0d85ac1935b 100644 --- a/Documentation/i2c/instantiating-devices +++ b/Documentation/i2c/instantiating-devices @@ -8,8 +8,8 @@ reason, the kernel code must instantiate I2C devices explicitly. There are several ways to achieve this, depending on the context and requirements. -Method 1: Declare the I2C devices by bus number ------------------------------------------------ +Method 1a: Declare the I2C devices by bus number +------------------------------------------------ This method is appropriate when the I2C bus is a system bus as is the case for many embedded systems. On such systems, each I2C bus has a number @@ -19,7 +19,7 @@ i2c_board_info which is registered by calling i2c_register_board_info(). Example (from omap2 h4): -static struct i2c_board_info __initdata h4_i2c_board_info[] = { +static struct i2c_board_info h4_i2c_board_info[] __initdata = { { I2C_BOARD_INFO("isp1301_omap", 0x2d), .irq = OMAP_GPIO_IRQ(125), @@ -51,6 +51,43 @@ The devices will be automatically unbound and destroyed when the I2C bus they sit on goes away (if ever.) +Method 1b: Declare the I2C devices via devicetree +------------------------------------------------- + +This method has the same implications as method 1a. The declaration of I2C +devices is here done via devicetree as subnodes of the master controller. + +Example: + + i2c1: i2c@400a0000 { + /* ... master properties skipped ... */ + clock-frequency = <100000>; + + flash@50 { + compatible = "atmel,24c256"; + reg = <0x50>; + }; + + pca9532: gpio@60 { + compatible = "nxp,pca9532"; + gpio-controller; + #gpio-cells = <2>; + reg = <0x60>; + }; + }; + +Here, two devices are attached to the bus using a speed of 100kHz. For +additional properties which might be needed to set up the device, please refer +to its devicetree documentation in Documentation/devicetree/bindings/. + + +Method 1c: Declare the I2C devices via ACPI +------------------------------------------- + +ACPI can also describe I2C devices. There is special documentation for this +which is currently located at Documentation/acpi/enumeration.txt. + + Method 2: Instantiate the devices explicitly -------------------------------------------- @@ -87,11 +124,11 @@ it may have different addresses from one board to the next (manufacturer changing its design without notice). In this case, you can call i2c_new_probed_device() instead of i2c_new_device(). -Example (from the pnx4008 OHCI driver): +Example (from the nxp OHCI driver): static const unsigned short normal_i2c[] = { 0x2c, 0x2d, I2C_CLIENT_END }; -static int __devinit usb_hcd_pnx4008_probe(struct platform_device *pdev) +static int usb_hcd_nxp_probe(struct platform_device *pdev) { (...) struct i2c_adapter *i2c_adap; @@ -100,7 +137,7 @@ static int __devinit usb_hcd_pnx4008_probe(struct platform_device *pdev) (...) i2c_adap = i2c_get_adapter(2); memset(&i2c_info, 0, sizeof(struct i2c_board_info)); - strlcpy(i2c_info.name, "isp1301_pnx", I2C_NAME_SIZE); + strlcpy(i2c_info.type, "isp1301_nxp", I2C_NAME_SIZE); isp1301_i2c_client = i2c_new_probed_device(i2c_adap, &i2c_info, normal_i2c, NULL); i2c_put_adapter(i2c_adap); |