Touch panel DTS 分析（MSM8994平台，Atmel 芯片）

在MSM8994平台，Touch panel的DTS写节点/kernel/arch/arm/boot/dts/qcom/msm8994-mtp.dtsi文件里。详细代码例如以下：

&soc {

[email protected] {

[email protected] {

compatible = "atmel,atmel_mxt_ts";

reg = <0x4a>;

interrupt-parent = <&msm_gpio>;

interrupts = <61 0x2008>;

avdd-supply  = <&pm8994_l22>;

vdd_io-supply = <&pm8994_l14>;

.........

};

};

在DTS节点中。我们主要看一下avdd-supply and vdd_io-supply两个属性。这两个属性在C代码里的使用方式例如以下：

/kernel/drivers/input/touchscreen/atmel_mxt_ts.c

mxt_probe_regulators(struct mxt_data *data)

{

........

data->reg_vdd_io = regulator_get(dev, "vdd_io");

........

data->reg_avdd = regulator_get(dev, "avdd");

........

}

/kernel/drivers/regulator/core.c

struct regulator *regulator_get(struct device *dev, const char *id)

{

return _regulator_get(dev, id, 0);

}

static struct regulator *_regulator_get(struct device *dev, const char *id, int exclusive)

{

.......

rdev = regulator_dev_lookup(dev, id, &ret);

if(rdev)

goto found;

......

}

static struct regulator_dev *regulator_dev_lookup(struct devic *dev, const char *supply, int *ret)

{

struct regulator_dev *r;

struct device_node *node;

........

/* first do a dt based lookup */

if (dev && dev->of_node) {

node = of_get_regulator(dev, supply)

if (node) {

list_for_each_entry(r, &regulator_list, list)

if ( r->dev.parent && node == r->dev.of_node)

return r;

........

}

}

}

static struct device_node *of_get_regulator(struct device *dev, const char *supply)

{

struct device_node *regnode = NULL;

char prop_name[32];

.......

snprintf(prop_name, 32, "%s-supply", supply);

regnode = of_parse_phandle(dev->of_node, prop_name, 0);

........

}

从上述代码大致上能够看到DTS里的vdd_io-supply and avdd-supply属性是怎样解析和使用的。

在mxt_probe()函数中将字符串“avdd”和“vdd_io”传给regulator_get()函数。一步步调用下来后，在of_get_regulator()函数中将字符串合并成DTS中符合要求的字符串属性。之后通过属性的值来找到对应的regulator_dev 结构体。

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