[PATCH]: 4afd67affc drivers/cmsis_dap: fix misleading error selecting not compiled backend

[gerrit]

This is an automated email from Gerrit.

"Tomas Vanek <van...@fbl.cz>" just uploaded a new patch set to Gerrit, which 
you can find at https://review.openocd.org/c/openocd/+/8760

-- gerrit

commit 4afd67affccac3e13b2c5b2d3603da67db12ec91
Author: Tomas Vanek <van...@fbl.cz>
Date:   Mon Feb 17 12:15:09 2025 +0100

    drivers/cmsis_dap: fix misleading error selecting not compiled backend
    
    If one of CMSIS-DAP backends was not compiled (due to
    missing library or configure --disable-cmsis-dap) and
    Tcl config explicitly selected it, a misleading message
    "invalid backend argument to cmsis-dap backend <backend>"
    was printed.
    
    Create dummy backends in struct cmsis_dap_backend
    to replace a not built backend.
    
    Check for NULL open backend method to distinguish
    the backend is dummy.
    
    Rework 'cmsis-dap backend' command to honour dummy
    backend. While on it print more helpful error messages.
    
    Change-Id: I8f12aeaaecf19302032870bc232e5135c1d935e7
    Signed-off-by: Tomas Vanek <van...@fbl.cz>

diff --git a/src/jtag/drivers/cmsis_dap.c b/src/jtag/drivers/cmsis_dap.c
index c8a7cf8fcd..be9ebaed58 100644
--- a/src/jtag/drivers/cmsis_dap.c
+++ b/src/jtag/drivers/cmsis_dap.c
@@ -39,14 +39,22 @@
 #include "cmsis_dap.h"
 #include "libusb_helper.h"
 
-static const struct cmsis_dap_backend *const cmsis_dap_backends[] = {
-#if BUILD_CMSIS_DAP_USB == 1
-       &cmsis_dap_usb_backend,
+/* Create a dummy backend for 'backend' command if real one does not build */
+#if BUILD_CMSIS_DAP_USB == 0
+const struct cmsis_dap_backend cmsis_dap_usb_backend = {
+       .name = "usb_bulk",
+};
 #endif
 
-#if BUILD_CMSIS_DAP_HID == 1
-       &cmsis_dap_hid_backend,
+#if BUILD_CMSIS_DAP_HID == 0
+const struct cmsis_dap_backend cmsis_dap_hid_backend = {
+       .name = "hid"
+};
 #endif
+
+static const struct cmsis_dap_backend *const cmsis_dap_backends[] = {
+       &cmsis_dap_usb_backend,
+       &cmsis_dap_hid_backend,
 };
 
 /* USB Config */
@@ -261,26 +269,32 @@ static int cmsis_dap_open(void)
                return ERROR_FAIL;
        }
 
+       int retval = ERROR_FAIL;
        if (cmsis_dap_backend >= 0) {
                /* Use forced backend */
                backend = cmsis_dap_backends[cmsis_dap_backend];
-               if (backend->open(dap, cmsis_dap_vid, cmsis_dap_pid, 
adapter_get_required_serial()) != ERROR_OK)
-                       backend = NULL;
+               if (backend->open)
+                       retval = backend->open(dap, cmsis_dap_vid, 
cmsis_dap_pid, adapter_get_required_serial());
+               else
+                       LOG_ERROR("Requested CMSIS-DAP backend is disabled by 
configure");
+
        } else {
                /* Try all backends */
                for (unsigned int i = 0; i < ARRAY_SIZE(cmsis_dap_backends); 
i++) {
                        backend = cmsis_dap_backends[i];
-                       if (backend->open(dap, cmsis_dap_vid, cmsis_dap_pid, 
adapter_get_required_serial()) == ERROR_OK)
+                       if (!backend->open)
+                               continue;
+
+                       retval = backend->open(dap, cmsis_dap_vid, 
cmsis_dap_pid, adapter_get_required_serial());
+                       if (retval == ERROR_OK)
                                break;
-                       else
-                               backend = NULL;
                }
        }
 
-       if (!backend) {
+       if (retval != ERROR_OK) {
                LOG_ERROR("unable to find a matching CMSIS-DAP device");
                free(dap);
-               return ERROR_FAIL;
+               return retval;
        }
 
        dap->backend = backend;
@@ -293,7 +307,8 @@ static int cmsis_dap_open(void)
 static void cmsis_dap_close(struct cmsis_dap *dap)
 {
        if (dap->backend) {
-               dap->backend->close(dap);
+               if (dap->backend->close)
+                       dap->backend->close(dap);
                dap->backend = NULL;
        }
 
@@ -2192,22 +2207,27 @@ COMMAND_HANDLER(cmsis_dap_handle_vid_pid_command)
 
 COMMAND_HANDLER(cmsis_dap_handle_backend_command)
 {
-       if (CMD_ARGC == 1) {
-               if (strcmp(CMD_ARGV[0], "auto") == 0) {
-                       cmsis_dap_backend = -1; /* autoselect */
-               } else {
-                       for (unsigned int i = 0; i < 
ARRAY_SIZE(cmsis_dap_backends); i++) {
-                               if (strcasecmp(cmsis_dap_backends[i]->name, 
CMD_ARGV[0]) == 0) {
+       if (CMD_ARGC != 1)
+               return ERROR_COMMAND_SYNTAX_ERROR;
+
+       if (strcmp(CMD_ARGV[0], "auto") == 0) {
+               cmsis_dap_backend = -1; /* autoselect */
+       } else {
+               for (unsigned int i = 0; i < ARRAY_SIZE(cmsis_dap_backends); 
i++) {
+                       if (strcasecmp(cmsis_dap_backends[i]->name, 
CMD_ARGV[0]) == 0) {
+                               if (cmsis_dap_backends[i]->open) {
                                        cmsis_dap_backend = i;
                                        return ERROR_OK;
                                }
-                       }
 
-                       command_print(CMD, "invalid backend argument to 
cmsis-dap backend <backend>");
-                       return ERROR_COMMAND_ARGUMENT_INVALID;
+                               command_print(CMD, "Requested cmsis-dap backend 
%s is disabled by configure",
+                                                         
cmsis_dap_backends[i]->name);
+                               return ERROR_NOT_IMPLEMENTED;
+                       }
                }
-       } else {
-               return ERROR_COMMAND_SYNTAX_ERROR;
+
+               command_print(CMD, "invalid argument %s to cmsis-dap backend", 
CMD_ARGV[0]);
+               return ERROR_COMMAND_ARGUMENT_INVALID;
        }
 
        return ERROR_OK;

--