how to include a static library in SDK?

這天忽然想build一個static binary, 才發現SDK沒有static library, 於是只好重新build一下SDK with static package.

brook@vista:~/oe-src$ . /opt/oecore-x86_64/environment-setup-cortexa7-neon-vfpv4-oe-linux-gnueabi brook@vista:~/oe-src$ ${CC} -static kobj.c /opt/oecore-x86_64/sysroots/x86_64-oesdk-linux/usr/libexec/arm-oe-linux-gnueabi/gcc/arm-oe-linux-gnueabi/5.3.0/real-ld: error: cannot find -lc /opt/oecore-x86_64/sysroots/cortexa7-neon-vfpv4-oe-linux-gnueabi/usr/lib/crt1.o(.text+0x28): error: undefined reference to '__libc_start_main' /opt/oecore-x86_64/sysroots/cortexa7-neon-vfpv4-oe-linux-gnueabi/usr/lib/crt1.o(.text+0x2c): error: undefined reference to 'abort' /opt/oecore-x86_64/sysroots/cortexa7-neon-vfpv4-oe-linux-gnueabi/usr/lib/crt1.o(.text+0x30): error: undefined reference to '__libc_csu_fini' /opt/oecore-x86_64/sysroots/cortexa7-neon-vfpv4-oe-linux-gnueabi/usr/lib/crt1.o(.text+0x38): error: undefined reference to '__libc_csu_init' /tmp/ccDJTrij.o:kobj.c:function init_hotplug_sock: error: undefined reference to 'bzero' /tmp/ccDJTrij.o:kobj.c:function init_hotplug_sock: error: undefined reference to 'getpid' /tmp/ccDJTrij.o:kobj.c:function init_hotplug_sock: error: undefined reference to 'socket' /tmp/ccDJTrij.o:kobj.c:function init_hotplug_sock: error: undefined reference to 'perror' /tmp/ccDJTrij.o:kobj.c:function init_hotplug_sock: error: undefined reference to 'setsockopt' /tmp/ccDJTrij.o:kobj.c:function init_hotplug_sock: error: undefined reference to 'bind' /tmp/ccDJTrij.o:kobj.c:function init_hotplug_sock: error: undefined reference to 'perror' /tmp/ccDJTrij.o:kobj.c:function init_hotplug_sock: error: undefined reference to 'close' /tmp/ccDJTrij.o:kobj.c:function main: error: undefined reference to 'memset' /tmp/ccDJTrij.o:kobj.c:function main: error: undefined reference to 'recv' /tmp/ccDJTrij.o:kobj.c:function main: error: undefined reference to 'puts' collect2: error: ld returned 1 exit status

這是因為沒有加入staticdev-pkgs
SDKIMAGE_FEATURES += "staticdev-pkgs"
SDKIMAGE_FEATURES相當於IMAGE_FEATURES, 但SDKIMAGE_FEATURES用於建立SDK image用, 如
$ bitbake -c populate_sdk imagename
SDKIMAGE_FEATURES可用的參數與IMAGE_FEATURES相同, 條列如下

• allow-empty-password: Allows Dropbear and OpenSSH to accept root logins and logins from accounts having an empty password string.
• dbg-pkgs: Installs debug symbol packages for all packages installed in a given image.
• debug-tweaks: Makes an image suitable for development (e.g. allows root logins without passwords and enables post-installation logging). See the 'allow-empty-password', 'empty-root-password', and 'post-install-logging' features in this list for additional information.
• dev-pkgs: Installs development packages (headers and extra library links) for all packages installed in a given image.
• doc-pkgs: Installs documentation packages for all packages installed in a given image.
• empty-root-password: Sets the root password to an empty string, which allows logins with a blank password.
• package-management: Installs package management tools and preserves the package manager database.
• post-install-logging: Enables logging postinstall script runs to the /var/log/postinstall.log file on first boot of the image on the target system.
• ptest-pkgs: Installs ptest packages for all ptest-enabled recipes.
• read-only-rootfs: Creates an image whose root filesystem is read-only. See the "Creating a Read-Only Root Filesystem" section in the Yocto Project Development Manual for more information.
• splash: Enables showing a splash screen during boot. By default, this screen is provided by psplash, which does allow customization. If you prefer to use an alternative splash screen package, you can do so by setting the SPLASH variable to a different package name (or names) within the image recipe or at the distro configuration level.
• staticdev-pkgs: Installs static development packages, which are static libraries (i.e. *.a files), for all packages installed in a given image.

Some image features are available only when you inherit the core-image class. The current list of these valid features is as follows:

• eclipse-debug: Provides Eclipse remote debugging support.
• hwcodecs: Installs hardware acceleration codecs.
• nfs-server: Installs an NFS server.
• qt4-pkgs: Supports Qt4/X11 and demo applications.
• ssh-server-dropbear: Installs the Dropbear minimal SSH server.
• ssh-server-openssh: Installs the OpenSSH SSH server, which is more full-featured than Dropbear. Note that if both the OpenSSH SSH server and the Dropbear minimal SSH server are present in IMAGE_FEATURES, then OpenSSH will take precedence and Dropbear will not be installed.
• tools-debug: Installs debugging tools such as strace and gdb. For information on GDB, see the "Debugging With the GNU Project Debugger (GDB) Remotely" section in the Yocto Project Development Manual. For information on tracing and profiling, see the Yocto Project Profiling and Tracing Manual.
• tools-profile: Installs profiling tools such as oprofile, exmap, and LTTng. For general information on user-space tools, see the "User-Space Tools" section in the Yocto Project Application Developer's Guide.
• tools-sdk: Installs a full SDK that runs on the device.
• tools-testapps: Installs device testing tools (e.g. touchscreen debugging).
• x11: Installs the X server.
• x11-base: Installs the X server with a minimal environment.
• x11-sato: Installs the OpenedHand Sato environment.

參考資料:
• https://www.yoctoproject.org/pipermail/yocto/2017-March/035377.html

ANSI C - identifiers naming rule

通常static變數/函數, 我都會以_var, _func為命名方式, 也符合C99 7.1.3標準,

7.1.3 Reserved identifiers

Each header declares or defines all identifiers listed in its associated subclause, and optionally declares or defines identifiers listed in its associated future library directions subclause and identifiers which are always reserved either for any use or for use as file scope identifiers.
-- All identifiers that begin with an underscore and either an uppercase letter or another underscore are always reserved for any use.
-- All identifiers that begin with an underscore are always reserved for use as identifiers with file scope in both the ordinary and tag name spaces.

Linux Kernel（17.2）- Common Device Tree API

properties的value可以是empty或是以下資料型態:

Text strings (null terminated) are represented with double quotes:
string-property = "a string";
'Cells' are 32 bit unsigned integers delimited by angle brackets:
cell-property = <0xbeef 123 0xabcd1234>;
Binary data is delimited with square brackets:
binary-property = [0x01 0x23 0x45 0x67];
Data of differing representations can be concatenated together using a comma:
mixed-property = "a string", [0x01 0x23 0x45 0x67], <0x12345678>;
Commas are also used to create lists of strings:
string-list = "red fish", "blue fish";

這章節介紹幾個API，用於存取這些常見的資料型態，會以下的DTS的內容進行parse

/ {
  node1 {
    compatible = "brook,dts-test";
    a-string-property = "A string";
    a-string-list-property = "first string", "second string";
    // hex is implied in byte arrays. no '0x' prefix is required
    a-byte-data-property = [01 23 34 56];
    child-node1 {
      first-child-property;
      second-child-property = <1>;
      a-string-property = "Hello, world";
    };
    child-node2 {
    };
  };
  
  node2 {
    compatible = "brook,dts-test";
    an-empty-property;
    a-cell-property = <1 2 3 4>; /* each number (cell) is a uint32 */
    child-node@1 {
    };
    child-node@2 {
    };
  };
};

• of_match_device(): Sanity check for device that device is matching with the node
• of_property_read_string(): To read string property
• of_property_count_strings(): Find and return the number of strings from a multiple strings property.
• of_property_read_string_index(): Read a string with index from string-list property.
• of_find_property(): Find and return the property pointer by giving named
• of_property_for_each_u32(): A macro to iterate the property to get all values
• of_property_read_bool(): Returns true if the property exist false otherwise
• of_find_node_by_name(): Find a node by its "name" property
• for_each_child_of_node(): Traverse all child device node for current device node

#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/of_device.h>

static struct of_device_id brook_dt_id[] = {
    {
     .compatible = "brook,dts-test",
    },
    {}
};

MODULE_DEVICE_TABLE(of, brook_dt_id);

static int brook_dts_probe(struct platform_device *pdev)
{
    const struct of_device_id *of_id;
    struct device_node *node, *child;
    struct property *pp;
    int i, ret, of_cnt, len;
    const char *str;
    const __be32 *cur;
    u32 val;

    // sanity check of_match_device() allows to get the matching entry
    of_id = of_match_device(brook_dt_id, &pdev->dev);
    if (!of_id) {
        pr_err("%s: of_id is NULL\n", __func__);
        return -1;
    }

    node = pdev->dev.of_node;
    // To read string property
    ret = of_property_read_string(node, "a-string-property", &str);
    if (!ret) {
        printk("a-string-property: %s\n", str);
    } else {
        printk("no a-string-property\n");
    }

    // Find and return the number of strings from a multiple strings property.
    of_cnt = of_property_count_strings(node, "a-string-list-property");
    if (of_cnt) {
        for (i = 0; i < of_cnt; i++) {
            ret = of_property_read_string_index(node, "a-string-list-property", i, &str);
            if (!ret) {
                printk("a-string-list-property[%d]: %s\n", i, str);
            }
        }
    }

    // to find aproperty named if arg2
    pp = of_find_property(node, "a-byte-data-property", &len);
    if (pp) {
        u8 *u8p = pp->value;
        printk("a-byte-data-property: len:%d, pp->len:%d", len, pp->length);
        for (i = 0; i < len; i++) {
            printk("a-byte-data-property:[%d] = %02x\n", i, u8p[i]);
        }
    }

    // to find aproperty named if arg2
    of_property_for_each_u32(node, "a-cell-property", pp, cur, val) {
        printk("a-cell-property: %04x/%04x\n", *cur, val);
    }

    // Returns true if the property exist false otherwise
    if (of_property_read_bool(node, "an-empty-property")) {
        printk("has an-empty-property\n");
    } else {
        printk("no an-empty-property\n");
    }

    // Traverse all child device node for current device node
    for_each_child_of_node(node, child) {
        printk("child name: %s\n", child->name);
    }

    // Find a node by its "name" property
    child = of_find_node_by_name(node, "child-node1");
    if (child) {
        printk("%s has a child %s\n", node->name, child->name);
    }

    return 0;
}

static int brook_dts_remove(struct platform_device *pdev)
{
    return 0;
}

static struct platform_driver brook_dts_platform_driver = {
    .probe = brook_dts_probe,
    .remove = brook_dts_remove,
    .driver = {
        .owner = THIS_MODULE,
        .name = "brook-dts",
        .of_match_table = brook_dt_id,
    },
};


static int __init brook_init_module(void)
{
    return platform_driver_register(&brook_dts_platform_driver);
}

static void __exit brook_exit_module(void)
{
    platform_driver_unregister(&brook_dts_platform_driver);
}

module_init(brook_init_module);
module_exit(brook_exit_module);
MODULE_LICENSE("GPL");

執行結果如下:

/ # insmod dts.ko
a-string-property: A string
a-string-list-property[0]: first string
a-string-list-property[1]: second string
a-byte-data-property: len:4, pp->len:4
a-byte-data-property:[0] = 01
a-byte-data-property:[1] = 23
a-byte-data-property:[2] = 34
a-byte-data-property:[3] = 56
no an-empty-property
child name: child-node1
child name: child-node2
node1 has a child child-node1
no a-string-property
a-cell-property: 1000000/0001
a-cell-property: 2000000/0002
a-cell-property: 3000000/0003
a-cell-property: 4000000/0004
has an-empty-property
child name: child-node
child name: child-node

以下摘錄http://www.myexception.cn/linux-unix/1910031.html, linux下devicetree中常用的of函數

linux下devicetree中常用的of函数
从device_node中获取信息：

int of_property_read_u8_array(const struct device_node *np, const char *propname,u8 *out_values, size_t sz);

int of_property_read_u16_array(const struct device_node *np, const char *propname,u16 *out_values, size_t sz);

int of_property_read_u32_array(const struct device_node *np, const char *propname,u32 *out_values, size_t sz);

从设备结点np中读取属性名为propname，类型为8、16、32、位整型数组的属性值，并放入out_values，sz指明了要读取的个数。


static inline int of_property_read_u8(const struct device_node *np,const char *propname,u8 *out_value) 

static inline int of_property_read_u16(const struct device_node *np,const char *propname,u8 *out_value) 

static inline int of_property_read_u32(const struct device_node *np,const char *propname,u8 *out_value) 

从设备结点np中读取属性名为propname，类型为8、16、32位的属性值，并放入out_values。实际上这里调用的就是sz为1的XXX_array函数。

 

int of_property_read_u32_index(const struct device_node *np,const char*propname,u32 index, u32 *out_value)

从设备结点np中读取属性名为propname的属性值中第index个u32数值给out_value

 

int of_property_read_u64(conststruct device_node *np, const char *propname,u64 *out_value)

从设备结点np中读取属性名为propname，类型为64位的属性值，并放入out_values

 

int of_property_read_string(struct device_node *np, const char *propname,const char**out_string)

从设备结点np中读取属性名为propname的字符串型属性值

 

int of_property_read_string_index(struct device_node *np, const char *propname,intindex, const char **output)

从设备结点np中读取属性名为propname的字符串型属性值数组中的第index个字符串

 

int of_property_count_strings(struct device_node *np, const char *propname)

从设备结点np中读取属性名为propname的字符串型属性值的个数

 

unsigned int irq_of_parse_and_map(struct device_node *dev, int index)

从设备节点dev中读取第index个irq号

 

int of_irq_to_resource(struct device_node *dev, int index, struct resource *r)

从设备节点dev中读取第index个irq号，并填充一个irq资源结构体

 

int of_irq_count(struct device_node *dev)

获取设备节点dev的irq个数


static inline bool of_property_read_bool(const struct device_node *np,const char *propname);

如果设备结点np含有propname属性，则返回true，否则返回false。一般用于检查空属性是否存在。

 

struct property* of_find_property(const struct device_node *np,const char *name,int *lenp)

根据name参数，在指定的设备结点np中查找匹配的property，并返回这个property

 

const void * of_get_property(const struct device_node *np, const char *name,int *lenp)

根据name参数，在指定的设备结点np中查找匹配的property，并返回这个property的属性值


struct device_node* of_get_parent(const struct device_node *node)

获得node节点的父节点的device node


int of_device_is_compatible(const struct device_node *device,const char *compat);

判断设备结点device的compatible属性是否包含compat指定的字符串


从of_allnodes中查找信息：

struct device_node* of_find_node_by_path(const char *path)
根据路径参数，在全局链表of_allnodes中，查找匹配的device_node


struct device_node* of_find_node_by_name(struct device_node *from,const char *name)
则根据name在全局链表of_allnodes中查找匹配的device_node,若from=NULL表示从头开始查找


struct device_node* of_find_node_by_type(struct device_node *from,const char *type)

根据设备类型在全局链表of_allnodes中查找匹配的device_node


struct device_node * of_find_compatible_node(struct device_node *from, const char*type, const char，*compatible);

根据compatible的属性值在全局链表of_allnodes中查找匹配的device_node，大多数情况下，from、type为NULL。

 

struct device_node* of_find_node_with_property(struct device_node *from,const char *prop_name)

根据节点属性的name在全局链表of_allnodes中查找匹配的device_node

 

struct device_node* of_find_node_by_phandle(phandle handle)

根据phandle在全局链表of_allnodes中查找匹配的device_node

 

杂：

void __iomem* of_iomap(struct device_node *node, int index);

通过设备结点直接进行设备内存区间的 ioremap()，index是内存段的索引。若设备结点的reg属性有多段，可通过index标示要ioremap的是哪一段，只有1段的情况，index为0

 

unsigned long __init of_get_flat_dt_root(void)

用来查找在dtb中的根节点，好像返回的都是0


int of_alias_get_id(struct device_node *np, const char *stem)

获取节点np对应的aliasid号

 

struct device_node* of_node_get(struct device_node *node)

void of_node_put(struct device_node *node)

device node计数增加/减少


const struct of_device_id* of_match_node(const struct of_device_id *matches,const struct device_node*node)

将matches数组中of_device_id结构的name和type与device node的compatible和type匹配，返回匹配度最高的of_device_id结构


platform_device和resource相关：

int of_address_to_resource(struct device_node *dev, int index,struct resource *r)

根据设备节点dev的reg属性值，填充资源结构体r。Index参数指明了使用reg属性中第几个属性值，一般设置为0，表示第一个。


struct platform_device* of_device_alloc(struct device_node *np,const char *bus_id,struct device *parent)

根据device node，bus_id以及父节点创建该设备的platform_device结构，同时会初始化它的resource成员。

 

int of_platform_bus_probe(struct device_node *root,const struct of_device_id *matches,struct device *parent)

遍历of_allnodes中的节点挂接到of_platform_bus_type总线上,由于此时of_platform_bus_type总线上还没有驱动,所以此时不进行匹配

 

int of_platform_populate(struct device_node *root,const struct of_device_id *matches,const struct of_dev_auxdata *lookup,struct device *parent)

遍历of_allnodes中的所有节点，生成并初始化所以节点的platform_device结构



struct platform_device* of_find_device_by_node(struct device_node *np)

根据device_node查找返回该设备对应的platform_device结构

參考資料:
• http://www.myexception.cn/linux-unix/1910031.html, linux下devicetree中常用的of函數
• https://saurabhsengarblog.wordpress.com/2015/11/28/device-tree-tutorial-arm/, Device Tree Tutorial (ARM)
• https://www.cnblogs.com/xiaojiang1025/p/6368260.html, Linux内核 设备树操作常用API