[Qemu-devel] [PATCH v4 3/3] Use help sub-sections to create sub-help options

[Laurent Vivier <lvivier@redhat.com>]

As '-help' output is 400 lines long it is not easy
to find information, but generally we know from
which area we want the information.

As sections already exist in the help description,
add some options to only display the wanted section.

'-help' now can take an optional parameter, which is
a comma separated list of sections to display:

    standard  display standard options
    block     display block options
    usb       display usb options
    display   display display options
    machine   display machine options
    network   display network options
    character display character options
    url       display url options
    bt        display bt options
    tpm       display tpm options
    kernel    display kernel options
    expert    display expert options
    object    display object options

'-help' without option displays all help sections.

Example:

    $ x86_64-softmmu/qemu-system-x86_64 -help kernel,usb
    QEMU emulator version 2.4.50, Copyright (c) 2003-2008 Fabrice Bellard
    usage: qemu-system-x86_64 [options] [disk_image]

    'disk_image' is a raw hard disk image for IDE hard disk 0

    Linux/Multiboot boot specific:
    -kernel bzImage use 'bzImage' as kernel image
    -append cmdline use 'cmdline' as kernel command line
    -initrd file    use 'file' as initial ram disk
    -dtb    file    use 'file' as device tree image

    USB options:
    -usb            enable the USB driver (will be the default soon)
    -usbdevice name add the host or guest USB device 'name'

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---
 qemu-options.hx | 120 +++++++++++++++++++++++++++++++++++++++---
 vl.c            | 160 ++++++++++++++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 265 insertions(+), 15 deletions(-)

diff --git a/qemu-options.hx b/qemu-options.hx
index ab1af02..ddf71db 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -6,17 +6,76 @@ HXCOMM construct option structures, enums and help message for specified
 HXCOMM architectures.
 HXCOMM HXCOMM can be used for comments, discarded from both texi and C
 
-DEFHEADING(Standard options:)
+#if defined(QEMU_HELP_SELECT_HELP) || !defined(QEMU_HELP_SELECT)
+#undef QEMU_HELP_SELECT_HELP
+DEFHEADING(Help/version options:)
 STEXI
 @table @option
 ETEXI
 
-DEF("help", 0, QEMU_OPTION_h,
-    "-h or -help     display this help and exit\n", QEMU_ARCH_ALL)
+DEF("help", HAS_ARG|IS_OPT, QEMU_OPTION_h,
+    "-h|-help [section][,...]\n"
+    "                list help options.\n"
+    "                You can provide the list of sections to display.\n"
+    "                available sections are:\n"
+    "                standard,block,usb,display,machine,network,character,\n"
+    "                url,bt,tpm,kernel,expert,object\n" , QEMU_ARCH_ALL)
 STEXI
-@item -h
+@item -help [section][,...]
 @findex -h
-Display help and exit
+list help options.
+
+You can provide the list of sections to display:
+@table @option
+@item standard
+display standard options
+@item block
+display block options
+@item usb
+display usb options
+@item display
+display display options
+@item machine
+display machine options
+@item network
+display network options
+@item character
+display character options
+@item url
+display url options
+@item bt
+display bt options
+@item tpm
+display tpm options
+@item kernel
+display kernel options
+@item expert
+display expert options
+@item object
+display object options
+@end table
+
+'-help' without option displays all help sections.
+
+@example
+Example:
+    $ x86_64-softmmu/qemu-system-x86_64 -help kernel,usb
+    QEMU emulator version 2.4.50, Copyright (c) 2003-2008 Fabrice Bellard
+    usage: qemu-system-x86_64 [options] [disk_image]
+
+    'disk_image' is a raw hard disk image for IDE hard disk 0
+
+    Linux/Multiboot boot specific:
+    -kernel bzImage use 'bzImage' as kernel image
+    -append cmdline use 'cmdline' as kernel command line
+    -initrd file    use 'file' as initial ram disk
+    -dtb    file    use 'file' as device tree image
+
+    USB options:
+    -usb            enable the USB driver (will be the default soon)
+    -usbdevice name add the host or guest USB device 'name'
+@end example
+
 ETEXI
 
 DEF("version", 0, QEMU_OPTION_version,
@@ -27,6 +86,19 @@ STEXI
 Display version information and exit
 ETEXI
 
+STEXI
+@end table
+ETEXI
+DEFHEADING()
+#endif
+
+#if defined(QEMU_HELP_SELECT_STANDARD) || !defined(QEMU_HELP_SELECT)
+#undef QEMU_HELP_SELECT_STANDARD
+DEFHEADING(Standard options:)
+STEXI
+@table @option
+ETEXI
+
 DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
     "-machine [type=]name[,prop[=value][,...]]\n"
     "                selects emulated machine ('-machine help' for list)\n"
@@ -410,7 +482,10 @@ STEXI
 @end table
 ETEXI
 DEFHEADING()
+#endif
 
+#if defined(QEMU_HELP_SELECT_BLOCK) || !defined(QEMU_HELP_SELECT)
+#undef QEMU_HELP_SELECT_BLOCK
 DEFHEADING(Block device options:)
 STEXI
 @table @option
@@ -798,7 +873,10 @@ STEXI
 @end table
 ETEXI
 DEFHEADING()
+#endif
 
+#if defined(QEMU_HELP_SELECT_USB) || !defined(QEMU_HELP_SELECT)
+#undef QEMU_HELP_SELECT_USB
 DEFHEADING(USB options:)
 STEXI
 @table @option
@@ -862,7 +940,10 @@ STEXI
 @end table
 ETEXI
 DEFHEADING()
+#endif
 
+#if defined(QEMU_HELP_SELECT_DISPLAY) || !defined(QEMU_HELP_SELECT)
+#undef QEMU_HELP_SELECT_DISPLAY
 DEFHEADING(Display options:)
 STEXI
 @table @option
@@ -1329,7 +1410,10 @@ STEXI
 @end table
 ETEXI
 ARCHHEADING(, QEMU_ARCH_I386)
+#endif
 
+#if defined(QEMU_HELP_SELECT_MACHINE) || !defined(QEMU_HELP_SELECT)
+#undef QEMU_HELP_SELECT_MACHINE
 ARCHHEADING(i386 target only:, QEMU_ARCH_I386)
 STEXI
 @table @option
@@ -1441,7 +1525,10 @@ STEXI
 @end table
 ETEXI
 DEFHEADING()
+#endif
 
+#if defined(QEMU_HELP_SELECT_NETWORK) || !defined(QEMU_HELP_SELECT)
+#undef QEMU_HELP_SELECT_NETWORK
 DEFHEADING(Network options:)
 STEXI
 @table @option
@@ -1995,7 +2082,10 @@ STEXI
 @end table
 ETEXI
 DEFHEADING()
+#endif
 
+#if defined(QEMU_HELP_SELECT_CHARACTER) || !defined(QEMU_HELP_SELECT)
+#undef QEMU_HELP_SELECT_CHARACTER
 DEFHEADING(Character device options:)
 STEXI
 
@@ -2273,7 +2363,10 @@ STEXI
 @end table
 ETEXI
 DEFHEADING()
+#endif
 
+#if defined(QEMU_HELP_SELECT_URL) || !defined(QEMU_HELP_SELECT)
+#undef QEMU_HELP_SELECT_URL
 DEFHEADING(Device URL Syntax:)
 STEXI
 
@@ -2482,7 +2575,10 @@ ETEXI
 STEXI
 @end table
 ETEXI
+#endif
 
+#if defined(QEMU_HELP_SELECT_BT) || !defined(QEMU_HELP_SELECT)
+#undef QEMU_HELP_SELECT_BT
 DEFHEADING(Bluetooth(R) options:)
 STEXI
 @table @option
@@ -2557,7 +2653,10 @@ STEXI
 @end table
 ETEXI
 DEFHEADING()
+#endif
 
+#if defined(QEMU_HELP_SELECT_TPM) || !defined(QEMU_HELP_SELECT)
+#undef QEMU_HELP_SELECT_TPM
 #ifdef CONFIG_TPM
 DEFHEADING(TPM device options:)
 
@@ -2632,7 +2731,10 @@ ETEXI
 DEFHEADING()
 
 #endif
+#endif
 
+#if defined(QEMU_HELP_SELECT_KERNEL) || !defined(QEMU_HELP_SELECT)
+#undef QEMU_HELP_SELECT_KERNEL
 DEFHEADING(Linux/Multiboot boot specific:)
 STEXI
 
@@ -2688,7 +2790,10 @@ STEXI
 @end table
 ETEXI
 DEFHEADING()
+#endif
 
+#if defined(QEMU_HELP_SELECT_EXPERT) || !defined(QEMU_HELP_SELECT)
+#undef QEMU_HELP_SELECT_EXPERT
 DEFHEADING(Debug/Expert options:)
 STEXI
 @table @option
@@ -3518,7 +3623,10 @@ STEXI
 Dump json-encoded vmstate information for current machine type to file
 in @var{file}
 ETEXI
+#endif
 
+#if defined(QEMU_HELP_SELECT_OBJECT) || !defined(QEMU_HELP_SELECT)
+#undef QEMU_HELP_SELECT_OBJECT
 DEFHEADING(Generic object creation)
 
 DEF("object", HAS_ARG, QEMU_OPTION_object,
@@ -3571,7 +3679,7 @@ to the RNG daemon.
 @end table
 
 ETEXI
-
+#endif
 
 HXCOMM This is the last statement. Insert new options before this line!
 STEXI
diff --git a/vl.c b/vl.c
index a4fa7e5..3da663f 100644
--- a/vl.c
+++ b/vl.c
@@ -1911,24 +1911,166 @@ static void version(void)
     printf("QEMU emulator version " QEMU_VERSION QEMU_PKGVERSION ", Copyright (c) 2003-2008 Fabrice Bellard\n");
 }
 
-static void help(int exitcode)
+#define QEMU_HELP_SELECT
+static void help_help(void)
 {
+#define QEMU_HELP_SELECT_HELP
+#define QEMU_OPTIONS_GENERATE_HELP
+#include "qemu-options-wrapper.h"
+}
+static void help_standard(void)
+{
+#define QEMU_HELP_SELECT_STANDARD
+#define QEMU_OPTIONS_GENERATE_HELP
+#include "qemu-options-wrapper.h"
+}
+static void help_block(void)
+{
+#define QEMU_HELP_SELECT_BLOCK
+#define QEMU_OPTIONS_GENERATE_HELP
+#include "qemu-options-wrapper.h"
+}
+static void help_usb(void)
+{
+#define QEMU_HELP_SELECT_USB
+#define QEMU_OPTIONS_GENERATE_HELP
+#include "qemu-options-wrapper.h"
+}
+static void help_display(void)
+{
+#define QEMU_HELP_SELECT_DISPLAY
+#define QEMU_OPTIONS_GENERATE_HELP
+#include "qemu-options-wrapper.h"
+}
+static void help_machine(void)
+{
+#define QEMU_HELP_SELECT_MACHINE
+#define QEMU_OPTIONS_GENERATE_HELP
+#include "qemu-options-wrapper.h"
+}
+static void help_network(void)
+{
+#define QEMU_HELP_SELECT_NETWORK
+#define QEMU_OPTIONS_GENERATE_HELP
+#include "qemu-options-wrapper.h"
+}
+static void help_character(void)
+{
+#define QEMU_HELP_SELECT_CHARACTER
+#define QEMU_OPTIONS_GENERATE_HELP
+#include "qemu-options-wrapper.h"
+}
+static void help_url(void)
+{
+#define QEMU_HELP_SELECT_URL
+#define QEMU_OPTIONS_GENERATE_HELP
+#include "qemu-options-wrapper.h"
+}
+static void help_bt(void)
+{
+#define QEMU_HELP_SELECT_BT
+#define QEMU_OPTIONS_GENERATE_HELP
+#include "qemu-options-wrapper.h"
+}
+#ifdef CONFIG_TPM
+static void help_tpm(void)
+{
+#define QEMU_HELP_SELECT_TPM
+#define QEMU_OPTIONS_GENERATE_HELP
+#include "qemu-options-wrapper.h"
+}
+#endif
+static void help_kernel(void)
+{
+#define QEMU_HELP_SELECT_KERNEL
+#define QEMU_OPTIONS_GENERATE_HELP
+#include "qemu-options-wrapper.h"
+}
+static void help_expert(void)
+{
+#define QEMU_HELP_SELECT_EXPERT
+#define QEMU_OPTIONS_GENERATE_HELP
+#include "qemu-options-wrapper.h"
+}
+static void help_object(void)
+{
+#define QEMU_HELP_SELECT_OBJECT
+#define QEMU_OPTIONS_GENERATE_HELP
+#include "qemu-options-wrapper.h"
+}
+#undef QEMU_HELP_SELECT
+
+#define SUBHELP(n) { .name = #n, .handler = help_##n }
+typedef struct {
+    const char *name;
+    void (*handler)(void);
+} QEMUHelpOptions;
+
+static QEMUHelpOptions help_handler[] = {
+    SUBHELP(help),
+    SUBHELP(standard),
+    SUBHELP(block),
+    SUBHELP(usb),
+    SUBHELP(display),
+    SUBHELP(machine),
+    SUBHELP(network),
+    SUBHELP(character),
+    SUBHELP(url),
+    SUBHELP(bt),
+#ifdef CONFIG_TPM
+    SUBHELP(tpm),
+#endif
+    SUBHELP(kernel),
+    SUBHELP(expert),
+    SUBHELP(object),
+    { NULL, NULL }
+};
+
+static void help(const char *optarg, int exitcode)
+{
+    const char *p, *e;
+    size_t l;
+    int i;
+
     version();
     printf("usage: %s [options] [disk_image]\n\n"
            "'disk_image' is a raw hard disk image for IDE hard disk 0\n\n",
             error_get_progname());
 
+    if (optarg == NULL) {
 #define QEMU_OPTIONS_GENERATE_HELP
 #include "qemu-options-wrapper.h"
 
-    printf("\nDuring emulation, the following keys are useful:\n"
-           "ctrl-alt-f      toggle full screen\n"
-           "ctrl-alt-n      switch to virtual console 'n'\n"
-           "ctrl-alt        toggle mouse and keyboard grab\n"
-           "\n"
-           "When using -nographic, press 'ctrl-a h' to get some help.\n");
+        printf("\nDuring emulation, the following keys are useful:\n"
+               "ctrl-alt-f      toggle full screen\n"
+               "ctrl-alt-n      switch to virtual console 'n'\n"
+               "ctrl-alt        toggle mouse and keyboard grab\n"
+               "\n"
+               "When using -nographic, press 'ctrl-a h' to get some help.\n");
+
+        exit(exitcode);
+    }
 
-    exit(exitcode);
+    p = optarg;
+    while (*p) {
+        e = strchr(p, ',');
+        l = !e ? strlen(p) : (size_t) (e - p);
+        for (i = 0; help_handler[i].handler; i++) {
+            if (l != strlen(help_handler[i].name)) {
+                continue;
+            }
+            if (strncmp(help_handler[i].name, p, l) == 0) {
+                break;
+            }
+        }
+        if (help_handler[i].handler) {
+            help_handler[i].handler();
+        } else {
+            printf("Unknown help option \"%.*s\"\n", (int)l, p);
+        }
+        p += l + (e != NULL);
+   }
+   exit(exitcode);
 }
 
 #define HAS_ARG 0x0001
@@ -3326,7 +3468,7 @@ int main(int argc, char **argv, char **envp)
                 select_soundhw (optarg);
                 break;
             case QEMU_OPTION_h:
-                help(0);
+                help(optarg, 0);
                 break;
             case QEMU_OPTION_version:
                 version();
-- 
2.1.0