Rather than creating stubs for every command that just return
QERR_UNSUPPORTED, use 'if' conditions in the QAPI schema to
fully exclude generation of the filesystem trimming commands
on POSIX platforms lacking required APIs.

The command will be rejected at QMP dispatch time instead,
avoiding reimplementing rejection by blocking the stub commands.
This changes the error message for affected commands from

    {"class": "CommandNotFound", "desc": "Command FOO has been disabled"}

to

    {"class": "CommandNotFound", "desc": "The command FOO has not been found"}

This has the additional benefit that the QGA protocol reference
now documents what conditions enable use of the command.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Konstantin Kostiuk <kkostiuk@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 qga/commands-posix.c | 13 -------------
 qga/qapi-schema.json |  9 ++++++---
 2 files changed, 6 insertions(+), 16 deletions(-)

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 9207cb7a8f..d92fa0ec87 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -1144,22 +1144,9 @@ error:
 
 #endif /* HAVE_GETIFADDRS */
 
-#if !defined(CONFIG_FSTRIM)
-GuestFilesystemTrimResponse *
-qmp_guest_fstrim(bool has_minimum, int64_t minimum, Error **errp)
-{
-    error_setg(errp, QERR_UNSUPPORTED);
-    return NULL;
-}
-#endif
-
 /* add unsupported commands to the list of blocked RPCs */
 GList *ga_command_init_blockedrpcs(GList *blockedrpcs)
 {
-#if !defined(CONFIG_FSTRIM)
-    blockedrpcs = g_list_append(blockedrpcs, g_strdup("guest-fstrim"));
-#endif
-
     return blockedrpcs;
 }
 
diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
index 62462f092c..21c65d1806 100644
--- a/qga/qapi-schema.json
+++ b/qga/qapi-schema.json
@@ -510,7 +510,8 @@
 ##
 { 'struct': 'GuestFilesystemTrimResult',
   'data': {'path': 'str',
-           '*trimmed': 'int', '*minimum': 'int', '*error': 'str'} }
+           '*trimmed': 'int', '*minimum': 'int', '*error': 'str'},
+  'if': { 'any': ['CONFIG_WIN32', 'CONFIG_FSTRIM'] } }
 
 ##
 # @GuestFilesystemTrimResponse:
@@ -520,7 +521,8 @@
 # Since: 2.4
 ##
 { 'struct': 'GuestFilesystemTrimResponse',
-  'data': {'paths': ['GuestFilesystemTrimResult']} }
+  'data': {'paths': ['GuestFilesystemTrimResult']},
+  'if': { 'any': ['CONFIG_WIN32', 'CONFIG_FSTRIM'] } }
 
 ##
 # @guest-fstrim:
@@ -542,7 +544,8 @@
 ##
 { 'command': 'guest-fstrim',
   'data': { '*minimum': 'int' },
-  'returns': 'GuestFilesystemTrimResponse' }
+  'returns': 'GuestFilesystemTrimResponse',
+  'if': { 'any': ['CONFIG_WIN32', 'CONFIG_FSTRIM'] } }
 
 ##
 # @guest-suspend-disk:
-- 
2.45.1