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auto.conf、 auto.conf.cmd、autoconf.h

1. 前言
2. 背景
3. 分析
- 3.1 語句 $ (Q) $(MAKE) -f $(srctree)/Makefile silentoldconfig
- 3.2 語句 $ (Q) $(MAKE) -f $(srctree)/scripts/Makefile.autoconf
4. 總結

1. 前言

　UBOOT版本：uboot2018.03，開發板myimx8mmek240。

2. 背景

在編譯構建目標時(如 make xxx)，頂層 Makefile 的 dot-config 變數值設置為 1 。如下：

#note： 頂層Makefile
dot-config     := 1
ifneq ($(filter $(no-dot-config-targets), $(MAKECMDGOALS)),)

ifeq ($(filter-out $(no-dot-config-targets), $(MAKECMDGOALS)),)

dot-config := 0

endif

endi

在頂層 Makefile 中：

#note： 頂層Makefile
KCONFIG_CONFIG	?= .config
export KCONFIG_CONFIG
ifeq ($(dot-config),1)

# Read in config

-include include/config/auto.conf                (1)
# Read in dependencies to all Kconfig* files, make sure to run

# oldconfig if changes are detected.

-include include/config/auto.conf.cmd            (2)
# To avoid any implicit rule to kick in, define an empty command

$(KCONFIG_CONFIG) include/config/auto.conf.cmd: ;

# If .config is newer than include/config/auto.conf, someone tinkered

# with it and forgot to run make oldconfig.

# if auto.conf.cmd is missing then we are probably in a cleaned tree so

# we execute the config step to be sure to catch updated Kconfig files

include/config/%.conf: $(KCONFIG_CONFIG) include/config/auto.conf.cmd

$(Q)$(MAKE) -f $(srctree)/Makefile silentoldconfig

@# If the following part fails, include/config/auto.conf should be

@# deleted so "make silentoldconfig" will be re-run on the next build.

$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.autoconf || 

{ rm -f include/config/auto.conf; false; }

@# include/config.h has been updated after "make silentoldconfig".

@# We need to touch include/config/auto.conf so it gets newer

@# than include/config.h.

@# Otherwise, 'make silentoldconfig' would be invoked twice.

$(Q)touch include/config/auto.conf
#endif

其中(1)(2)兩行嘗試包含 auto.conf 和 auto.conf.cmd 這兩個文件。由於使用 -include 進行聲明，所以即使這兩個文件不存在也不會報錯退出，比如在第 1 次編譯uboot，且已經配置好 .config 文件時，這兩個文件還未生成。

假如我們已經編譯好了xxx_deconfig 這個目標，那麼我們會在 include/config 這個目錄下看到 auto.conf 和 auto.conf.cmd 這兩個文件。
在這裡插入圖片描述
從 include/config/%.conf: $(KCONFIG_CONFIG) include/config/auto.conf.cmd 這條規則可以知道，auto.conf 文件依賴於 $(KCONFIG_CONFIG) 和 include/config/auto.conf.cmd 。其中 $(KCONFIG_CONFIG) 變數的值就是 .config 這個配置文件。

3. 分析

# To avoid any implicit rule to kick in, define an empty command
$(KCONFIG_CONFIG) include/config/auto.conf.cmd: ;

現在仍然假設 auto.conf 和 auto.conf.cmd 還沒有生成，那麼由上面這條語句可以知道，該語句中的目標沒有依賴，也沒有生成它的規則命令，所以可想 GNU Make 本身無法生成 auto.conf.cmd 的。然後該條語句後面的一個分號表明，這兩個目標被強制是最新的。所以下麵標註的這幾條命令得以執行：

#note： 頂層Makefile
include/config/%.conf: $(KCONFIG_CONFIG) include/config/auto.conf.cmd
	$(Q)$(MAKE) -f $(srctree)/Makefile silentoldconfig                          （1）
	@# If the following part fails, include/config/auto.conf should be
	@# deleted so "make silentoldconfig" will be re-run on the next build.
	$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.autoconf || \
		{ rm -f include/config/auto.conf; false; }                              （2）
	@# include/config.h has been updated after "make silentoldconfig".
	@# We need to touch include/config/auto.conf so it gets newer
	@# than include/config.h.
	@# Otherwise, 'make silentoldconfig' would be invoked twice.
	$(Q)touch include/config/auto.conf                                          （3）

3.1 語句 $ (Q) $(MAKE) -f $(srctree)/Makefile silentoldconfig

這裡我們看到要生成一個目標 silentoldconfig ，這個目標定義在 scripts/kconfig/Makefile 中。因為這裡使用 -f 選項重新指定了頂層 Makefile，而目標又是 silentoldconfig ，所以該命令最終會在頂層 Makefile 里執行：

#note： 頂層Makefile
# We need some generic definitions (do not try to remake the file).
scripts/Kbuild.include: ;
include scripts/Kbuild.include            //註意這個引用
......
%config: scripts_basic outputmakefile FORCE
	$(Q)$(MAKE) $(build)=scripts/kconfig $@

在scripts/kconfig/Makefile中(至於為什麼會引用scripts/kconfig/Makefile，參見UBOOT編譯— make xxx_deconfig過程詳解(一)4.1.4.3 小節)

# note：scripts/kconfig/Makefile
ifdef KBUILD_KCONFIG
Kconfig := $(KBUILD_KCONFIG)
else
Kconfig := Kconfig
endif
......
silentoldconfig: $(obj)/conf
	$(Q)mkdir -p include/config include/generated
	$(Q)test -e include/generated/autoksyms.h || \
	    touch   include/generated/autoksyms.h
	$< $(silent) --$@ $(Kconfig)

從上面看到，silentoldconfig 目標需要依賴 conf 這個程式，該程式也在 scripts/kconfig 目錄下生成。
$ < $ (silent) --$ @ $ (Kconfig)該條命令相當於 scripts/kconfig/conf -s --myimx8mmek240-8mm-2g_defconfig .config 。
其中scripts/kconfig/conf的生成：參見UBOOT編譯— make xxx_deconfig過程詳解(一)4.4小節。

conf 程式的源代碼的主函數在同目錄的 conf.c 文件中，在 main() 函數中看到：

#note：/scripts/kconfig/conf.c
enum input_mode {
	oldaskconfig,
	silentoldconfig, //1
	oldconfig,
	allnoconfig,
	allyesconfig,
	allmodconfig,
	alldefconfig,
	randconfig,
	defconfig,
	savedefconfig,
	listnewconfig,
	olddefconfig,
} input_mode = oldaskconfig;
......

while ((opt = getopt_long(ac, av, "s", long_opts, NULL)) != -1) {

if (opt == 's') {

conf_set_message_callback(NULL);

continue;

}

input_mode = (enum input_mode)opt;

switch (opt) {

case silentoldconfig:

sync_kconfig = 1;

break;

所以，
(1) 在使用 s 參數時，message的回調函數被註冊為空，即conf_message函數無輸出列印；
(2) 同時參數opt被賦值為1，等價於silentoldconfig；sync_kconfig = 1；
(3) input_mode = silentoldconfig；

同樣在 main() 函數還看到：

#note：/scripts/kconfig/confdata.c
const char *conf_get_configname(void)
{
	char *name = getenv("KCONFIG_CONFIG");
<span class="token keyword">return</span> name <span class="token operator">?</span> name <span class="token operator">:</span> <span class="token string">".config"</span><span class="token punctuation">;</span>

}
#note：/scripts/kconfig/conf.c

if (sync_kconfig) {

name = conf_get_configname();

if (stat(name, &tmpstat)) {

fprintf(stderr, _("\n"

" Configuration file "%s" not found!\n"

"\n"

" Please run some configurator (e.g. "make oldconfig" or\n"

"*** "make menuconfig" or "make xconfig").\n"

"***\n"), name);

exit(1);

}

}

上面代碼中，如果我們從未配置過UBOOT，那麼就會列印出錯誤信息，然後退出。這裡假設已經配置過UBOOT(參見UBOOT編譯— make xxx_deconfig過程詳解(一)），並生成了 .config 文件，那麼在 main() 函數中會來到：

#note：/scripts/kconfig/conf.c
	switch (input_mode) {
	case defconfig:
		if (!defconfig_file)
			defconfig_file = conf_get_default_confname();
		if (conf_read(defconfig_file)) {
			printf(_("***\n"
				"*** Can't find default configuration \"%s\"!\n"
				"***\n"), defconfig_file);
			exit(1);
		}
		break;
	case savedefconfig:
	case silentoldconfig:
	case oldaskconfig:
	case oldconfig:
	case listnewconfig:
	case olddefconfig:
		conf_read(NULL);
		break;

前面已經講過由於使用 -s 選項，則 input_mode 為silentoldconfig，所以這裡會執行 conf_read(NULL)函數。
conf_read(NULL) 函數用來讀取 .config 文件。讀取的各種相關內容主要存放在一個 struct symbol 結構鏈表裡，而各個結構的相關指針則放在一個 symbol_hash[] 的數組中，對於數組中元素的尋找通過 fnv32 哈希演算法進行定位。

最後會來到 conf.c 中的底部：

#note：/scripts/kconfig/conf.c
	if (sync_kconfig) {
		/* silentoldconfig is used during the build so we shall update autoconf.
		 * All other commands are only used to generate a config.
		 */
		if (conf_get_changed() && conf_write(NULL)) {
			fprintf(stderr, _("\n*** Error during writing of the configuration.\n\n"));
			exit(1);
		}
		if (conf_write_autoconf()) {
			fprintf(stderr, _("\n*** Error during update of the configuration.\n\n"));
			return 1;
		}
	} else if (input_mode == savedefconfig) {
		if (conf_write_defconfig(defconfig_file)) {
			fprintf(stderr, _("n*** Error while saving defconfig to: %s\n\n"),
				defconfig_file);
			return 1;
		}
	} else if (input_mode != listnewconfig) {
		if (conf_write(NULL)) {
			fprintf(stderr, _("\n*** Error during writing of the configuration.\n\n"));
			exit(1);
		}
	}

實際上也只有當處理 silentoldconfig 目標時 sync_kconfig 變數才會為 1 。
（1）在 if (conf_get_changed() && conf_write(NULL)) 這個判斷里，conf_get_changed() 函數判斷 .config 文件是否做過變動，如果是，那麼會調用 conf_write(NULL) 來重新寫 .config 文件。實際上，對於 defconfig, oldconfig,menuconfig,***xxx_deconfig 等目標來說，conf 程式最終也是調用 conf_write() 函數將配置結果寫入 .config 文件中。
（2）確保了 .config 已經最新後，那麼調用 conf_write_autoconf() 生成 auto.conf，auto.conf.cmd 以及 autoconf.h 這 3 個文件。
來到 conf_write_autoconf() 函數：

#note：/scripts/kconfig/confdata.c
int conf_write_autoconf(void)
{
	struct symbol *sym;
	const char *name;
	FILE *out, *tristate, *out_h;
	int i;
<span class="token function">sym_clear_all_valid</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token function">file_write_dep</span><span class="token punctuation">(</span><span class="token string">"include/config/auto.conf.cmd"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">conf_split_config</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
	<span class="token keyword">return</span> <span class="token number">1</span><span class="token punctuation">;</span>

......

在 conf_write_autoconf() 里，調用 file_write_dep(“include/config/auto.conf.cmd”); 函數將相關內容寫入 auto.conf.cmd 文件。在生成的 auto.conf.cmd 文件中可以看到：

deps_config := \
	test/overlay/Kconfig \
	test/env/Kconfig \
	test/dm/Kconfig \
<span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>

board<span class="token operator">/</span>abilis<span class="token operator">/</span>tb100<span class="token operator">/</span>Kconfig \
arch<span class="token operator">/</span>arc<span class="token operator">/</span>Kconfig \
arch<span class="token operator">/</span>Kconfig \
Kconfig

include/config/auto.conf: 

$(deps_config)
ifneq "$(UBOOTVERSION)" "2018.03"

include/config/auto.conf: FORCE

endif
$(deps_config): ;

可以看到 auto.conf 文件中的內容依賴於 $(deps_config) 變數里定義的東西，這些東西基本上是各個目錄下的 Kconfig 以及其它一些相關文件。

仍然在 conf_write_autoconf() 里，分別建立了 .tmpconfig，.tmpconfig_tristate 和 .tmpconfig.h 這 3 個臨時文件,然後將文件頭的註釋部分分別寫入到這幾個臨時文件中，接著在 for_all_symbols(i, sym) 這個迴圈里(是一個巨集)里將相關內容分別寫入到這幾個文件中。

#note：/scripts/kconfig/confdata.c
	out = fopen(".tmpconfig", "w");
	if (!out)
		return 1;
tristate <span class="token operator">=</span> <span class="token function">fopen</span><span class="token punctuation">(</span><span class="token string">".tmpconfig_tristate"</span><span class="token punctuation">,</span> <span class="token string">"w"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>tristate<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
	<span class="token function">fclose</span><span class="token punctuation">(</span>out<span class="token punctuation">)</span><span class="token punctuation">;</span>
	<span class="token keyword">return</span> <span class="token number">1</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

out_h <span class="token operator">=</span> <span class="token function">fopen</span><span class="token punctuation">(</span><span class="token string">".tmpconfig.h"</span><span class="token punctuation">,</span> <span class="token string">"w"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>out_h<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
	<span class="token function">fclose</span><span class="token punctuation">(</span>out<span class="token punctuation">)</span><span class="token punctuation">;</span>
	<span class="token function">fclose</span><span class="token punctuation">(</span>tristate<span class="token punctuation">)</span><span class="token punctuation">;</span>
	<span class="token keyword">return</span> <span class="token number">1</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>

<span class="token function">conf_write_heading</span><span class="token punctuation">(</span>out<span class="token punctuation">,</span> <span class="token operator">&amp;</span>kconfig_printer_cb<span class="token punctuation">,</span> <span class="token constant">NULL</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token function">conf_write_heading</span><span class="token punctuation">(</span>tristate<span class="token punctuation">,</span> <span class="token operator">&amp;</span>tristate_printer_cb<span class="token punctuation">,</span> <span class="token constant">NULL</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token function">conf_write_heading</span><span class="token punctuation">(</span>out_h<span class="token punctuation">,</span> <span class="token operator">&amp;</span>header_printer_cb<span class="token punctuation">,</span> <span class="token constant">NULL</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token function">for_all_symbols</span><span class="token punctuation">(</span>i<span class="token punctuation">,</span> sym<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span>
	<span class="token function">sym_calc_value</span><span class="token punctuation">(</span>sym<span class="token punctuation">)</span><span class="token punctuation">;</span>
	<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span><span class="token punctuation">(</span>sym<span class="token operator">-&gt;</span>flags <span class="token operator">&amp;</span> SYMBOL_WRITE<span class="token punctuation">)</span> <span class="token operator">||</span> <span class="token operator">!</span>sym<span class="token operator">-&gt;</span>name<span class="token punctuation">)</span>
		<span class="token keyword">continue</span><span class="token punctuation">;</span>

	<span class="token comment">/* write symbol to auto.conf, tristate and header files */</span>
	<span class="token function">conf_write_symbol</span><span class="token punctuation">(</span>out<span class="token punctuation">,</span> sym<span class="token punctuation">,</span> <span class="token operator">&amp;</span>kconfig_printer_cb<span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token keyword">void</span> <span class="token operator">*</span><span class="token punctuation">)</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

	<span class="token function">conf_write_symbol</span><span class="token punctuation">(</span>tristate<span class="token punctuation">,</span> sym<span class="token punctuation">,</span> <span class="token operator">&amp;</span>tristate_printer_cb<span class="token punctuation">,</span> <span class="token punctuation">(</span><span class="token keyword">void</span> <span class="token operator">*</span><span class="token punctuation">)</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

	<span class="token function">conf_write_symbol</span><span class="token punctuation">(</span>out_h<span class="token punctuation">,</span> sym<span class="token punctuation">,</span> <span class="token operator">&amp;</span>header_printer_cb<span class="token punctuation">,</span> <span class="token constant">NULL</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>
<span class="token function">fclose</span><span class="token punctuation">(</span>out<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">fclose</span><span class="token punctuation">(</span>tristate<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">fclose</span><span class="token punctuation">(</span>out_h<span class="token punctuation">)</span><span class="token punctuation">;</span>

在這裡插入圖片描述

在最後一段代碼中，將這幾個臨時文件進行改名：

#note：/scripts/kconfig/confdata.c
const char *conf_get_autoconfig_name(void)
{
	char *name = getenv("KCONFIG_AUTOCONFIG");
<span class="token keyword">return</span> name <span class="token operator">?</span> name <span class="token operator">:</span> <span class="token string">"include/config/auto.conf"</span><span class="token punctuation">;</span>

}
......
name <span class="token operator">=</span> <span class="token function">getenv</span><span class="token punctuation">(</span><span class="token string">"KCONFIG_AUTOHEADER"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>name<span class="token punctuation">)</span>
	name <span class="token operator">=</span> <span class="token string">"include/generated/autoconf.h"</span><span class="token punctuation">;</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">rename</span><span class="token punctuation">(</span><span class="token string">".tmpconfig.h"</span><span class="token punctuation">,</span> name<span class="token punctuation">)</span><span class="token punctuation">)</span>
	<span class="token keyword">return</span> <span class="token number">1</span><span class="token punctuation">;</span>
name <span class="token operator">=</span> <span class="token function">getenv</span><span class="token punctuation">(</span><span class="token string">"KCONFIG_TRISTATE"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>name<span class="token punctuation">)</span>
	name <span class="token operator">=</span> <span class="token string">"include/config/tristate.conf"</span><span class="token punctuation">;</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">rename</span><span class="token punctuation">(</span><span class="token string">".tmpconfig_tristate"</span><span class="token punctuation">,</span> name<span class="token punctuation">)</span><span class="token punctuation">)</span>
	<span class="token keyword">return</span> <span class="token number">1</span><span class="token punctuation">;</span>
name <span class="token operator">=</span> <span class="token function">conf_get_autoconfig_name</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment">/*
 * This must be the last step, kbuild has a dependency on auto.conf
 * and this marks the successful completion of the previous steps.
 */</span>
<span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token function">rename</span><span class="token punctuation">(</span><span class="token string">".tmpconfig"</span><span class="token punctuation">,</span> name<span class="token punctuation">)</span><span class="token punctuation">)</span>
	<span class="token keyword">return</span> <span class="token number">1</span><span class="token punctuation">;</span>

從上面可以看到，分別生成了以下幾個文件：

include/generated/autoconf.h 
include/config/tristate.conf 
include/config/auto.conf

3.2 語句 $ (Q) $(MAKE) -f $(srctree)/scripts/Makefile.autoconf

由於篇幅的原因，放在下一講。

4. 總結

（1）auto.conf 和 .config 的差別是：auto.conf 里去掉了 .config 中的註釋項目以及空格行，其它的都一樣。

（2） include/generated/autoconf.h 頭文件由UBOOT本身使用，主要用來預處理 C 代碼，把auto.conf中的定義轉換成C語言的巨集定義。。

（1）在 .config 或 auto.conf 中後接"=y"的項，如：
　 CONFIG_OF_LIBFDT=y
　在 autoconfig.h 中會被定義為：
#define CONFIG_OF_LIBFDT 1

（2）在 .config 或 auto.conf 中後接字元串值的項，如：
　 CONFIG_DEFAULT_FDT_FILE="myimx8mmek240-8mm.dtb"
　在 autoconfig.h 中會被定義為：
#define CONFIG_DEFAULT_FDT_FILE "myimx8mmek240-8mm.dtb"

（3）在 .config 或 auto.conf 中後接數值的項，如：
　 CONFIG_SDP_LOADADDR=0x40400000
　在 autoconfig.h 中會被定義為：
#define CONFIG_SDP_LOADADDR 0x40400000

UBOOT編譯--- include/config/auto.conf、 include/config/auto.conf.cmd、 include/generated/autoconf.h (二)