1.. SPDX-License-Identifier: GPL-2.0+
2
3Implementing shell commands
4===========================
5
6Command definition
7------------------
8
9Commands are added to U-Boot by creating a new command structure.
10This is done by first including command.h, then using the U_BOOT_CMD() or the
11U_BOOT_CMD_COMPLETE macro to fill in a struct cmd_tbl structure.
12
13.. code-block:: c
14
15    U_BOOT_CMD(name, maxargs, repeatable, command, "usage", "help")
16    U_BOOT_CMD_COMPLETE(name, maxargs, repeatable, command, "usage, "help", comp)
17
18name
19    The name of the command. This is **not** a string.
20
21maxargs
22    The maximum number of arguments this function takes including
23    the command itself.
24
25repeatable
26    Either 0 or 1 to indicate if autorepeat is allowed.
27
28command
29    Pointer to the command function. This is the function that is
30    called when the command is issued.
31
32usage
33    Short description. This is a string.
34
35help
36    Long description. This is a string. The long description is
37    only available if CONFIG_SYS_LONGHELP is defined.
38
39comp
40    Pointer to the completion function. May be NULL.
41    This function is called if the user hits the TAB key while
42    entering the command arguments to complete the entry. Command
43    completion is only available if CONFIG_AUTO_COMPLETE is defined.
44
45Sub-command definition
46----------------------
47
48Likewise an array of struct cmd_tbl holding sub-commands can be created using
49either of the following macros:
50
51.. code-block:: c
52
53    U_BOOT_CMD_MKENT(name, maxargs, repeatable, command, "usage", "help")
54    U_BOOT_CMD_MKENTCOMPLETE(name, maxargs, repeatable, command, "usage, "help", comp)
55
56This table has to be evaluated in the command function of the main command, e.g.
57
58.. code-block:: c
59
60    static struct cmd_tbl cmd_sub[] = {
61        U_BOOT_CMD_MKENT(foo, CONFIG_SYS_MAXARGS, 1, do_foo, "", ""),
62        U_BOOT_CMD_MKENT(bar, CONFIG_SYS_MAXARGS, 1, do_bar, "", ""),
63    };
64
65    static int do_cmd(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
66    {
67        struct cmd_tbl *cp;
68
69        if (argc < 2)
70                return CMD_RET_USAGE;
71
72        /* drop sub-command argument */
73        argc--;
74        argv++;
75
76        cp = find_cmd_tbl(argv[0], cmd_ut_sub, ARRAY_SIZE(cmd_sub));
77
78        if (cp)
79            return cp->cmd(cmdtp, flag, argc, argv);
80
81        return CMD_RET_USAGE;
82    }
83
84Command function
85----------------
86
87The command function pointer has to be of type
88
89.. code-block:: c
90
91    int (*cmd)(struct cmd_tbl *cmdtp, int flag, int argc, const char *argv[]);
92
93cmdtp
94    Table entry describing the command (see above).
95
96flag
97    A bitmap which may contain the following bits
98
99    * CMD_FLAG_REPEAT - The last command is repeated.
100    * CMD_FLAG_BOOTD  - The command is called by the bootd command.
101    * CMD_FLAG_ENV    - The command is called by the run command.
102
103argc
104    Number of arguments including the command.
105
106argv
107    Arguments.
108
109Allowable return value are:
110
111CMD_RET_SUCCESS
112    The command was successfully executed.
113
114CMD_RET_FAILURE
115    The command failed.
116
117CMD_RET_USAGE
118    The command was called with invalid parameters. This value
119    leads to the display of the usage string.
120
121Completion function
122-------------------
123
124The completion function pointer has to be of type
125
126.. code-block:: c
127
128    int (*complete)(int argc, char *const argv[], char last_char,
129                    int maxv, char *cmdv[]);
130
131argc
132    Number of arguments including the command.
133
134argv
135    Arguments.
136
137last_char
138    The last character in the command line buffer.
139
140maxv
141    Maximum number of possible completions that may be returned by
142    the function.
143
144cmdv
145    Used to return possible values for the last argument. The last
146    possible completion must be followed by NULL.
147
148The function returns the number of possible completions (without the terminating
149NULL value).
150
151Behind the scene
152----------------
153
154The structure created is named with a special prefix and placed by
155the linker in a special section using the linker lists mechanism
156(see include/linker_lists.h)
157
158This makes it possible for the final link to extract all commands
159compiled into any object code and construct a static array so the
160command array can be iterated over using the linker lists macros.
161
162The linker lists feature ensures that the linker does not discard
163these symbols when linking full U-Boot even though they are not
164referenced in the source code as such.
165
166If a new board is defined do not forget to define the command section
167by writing in u-boot.lds ($(srctree)/board/boardname/u-boot.lds) these
1683 lines:
169
170.. code-block:: c
171
172    .u_boot_list : {
173        KEEP(*(SORT(.u_boot_list*)));
174    }
175
176Writing tests
177-------------
178
179All new commands should have tests. Tests for existing commands are very
180welcome.
181
182It is fairly easy to write a test for a command. Enable it in sandbox, and
183then add code that runs the command and checks the output.
184
185Here is an example:
186
187.. code-block:: c
188
189    /* Test 'acpi items' command */
190    static int dm_test_acpi_cmd_items(struct unit_test_state *uts)
191    {
192        struct acpi_ctx ctx;
193        void *buf;
194
195        buf = malloc(BUF_SIZE);
196        ut_assertnonnull(buf);
197
198        ctx.current = buf;
199        ut_assertok(acpi_fill_ssdt(&ctx));
200        console_record_reset();
201        run_command("acpi items", 0);
202        ut_assert_nextline("dev 'acpi-test', type 1, size 2");
203        ut_assert_nextline("dev 'acpi-test2', type 1, size 2");
204        ut_assert_console_end();
205
206        ctx.current = buf;
207        ut_assertok(acpi_inject_dsdt(&ctx));
208        console_record_reset();
209        run_command("acpi items", 0);
210        ut_assert_nextline("dev 'acpi-test', type 2, size 2");
211        ut_assert_nextline("dev 'acpi-test2', type 2, size 2");
212        ut_assert_console_end();
213
214        console_record_reset();
215        run_command("acpi items -d", 0);
216        ut_assert_nextline("dev 'acpi-test', type 2, size 2");
217        ut_assert_nextlines_are_dump(2);
218        ut_assert_nextline("%s", "");
219        ut_assert_nextline("dev 'acpi-test2', type 2, size 2");
220        ut_assert_nextlines_are_dump(2);
221        ut_assert_nextline("%s", "");
222        ut_assert_console_end();
223
224        return 0;
225    }
226    DM_TEST(dm_test_acpi_cmd_items, UT_TESTF_SCAN_PDATA | UT_TESTF_SCAN_FDT);
227