docs: add at driver warnings (estkme-group#385)

* docs: add at driver warnings

* chore(CMake): disable APDU AT backend by default

* refactor(driver/at): replace warning message macro with function

* docs(at): refine warning messages for clarity and consistency

* refactor(at): move warning message implementation to at_helpers.c

* docs(at): update warning messages for clarity and compliance with ETSI TS 127 007

Author: septs

.github/scripts/build-ci.sh

@@ -19,7 +19,7 @@ cd "$BUILD"
 
 case "${1:-}" in
 make)
-    cmake "$WORKSPACE" -DSTANDALONE_MODE=ON
+    cmake "$WORKSPACE" -DSTANDALONE_MODE=ON -DLPAC_WITH_APDU_AT=ON
     make -j VERBOSE=1
     make DESTDIR="$PKGDIR" install
     copy-license "$PKGDIR/executables"

docs/backends/at.md

@@ -1,7 +1,22 @@
 # AT APDU Backend
 
-The AT Backend is used to communicate with the eUICC via AT commands over a serial interface.
-It is commonly used with cellular modems that support AT commands for SIM card management.
+> [!CAUTION]
+>
+> **FOR DEMO PURPOSES ONLY.**
+> 
+> Only requests that strictly follow the [ETSI TS 127 007] specification are supported. \
+> Requests outside the specification will be **REJECTED**.
+>
+> Some operations (e.g: download, delete, etc.), may fail due to insufficient response time. \
+> The Maximum Response Time is typically 300ms, which is insufficient for many eUICC operations.
+
+The AT Backend is used to communicate with the eUICC via AT commands over a serial port. \
+It is commonly used with cellular modems that support AT commands for eUICC management.
+
+Not all cellular modems support the required AT commands for eUICC management. \
+Please refer to your modem's documentation to verify compatibility.
+
+[ETSI TS 127 007]: https://www.etsi.org/deliver/etsi_ts/127000_127099/127007/15.02.00_60/ts_127007v150200p.pdf
 
 ## Unix-like platform
 

driver/CMakeLists.txt

@@ -1,5 +1,5 @@
 option(LPAC_WITH_APDU_PCSC "Build APDU PCSC Backend (requires PCSC libraries)" ON)
-option(LPAC_WITH_APDU_AT "Build APDU AT Backend" ON)
+option(LPAC_WITH_APDU_AT "Build APDU AT Backend" OFF)
 option(LPAC_WITH_APDU_GBINDER "Build APDU Gbinder backend for libhybris devices (requires gbinder headers)" OFF)
 option(LPAC_WITH_APDU_QMI "Build QMI backend for Qualcomm devices (requires libqmi)" OFF)
 option(LPAC_WITH_APDU_QMI_QRTR "Build QMI-over-QRTR backend for Qualcomm devices (requires libqrtr and libqmi headers)" OFF)
@@ -68,6 +68,8 @@ if (LPAC_WITH_APDU_PCSC)
 endif ()
 
 if (LPAC_WITH_APDU_AT)
+    message(WARNING "LPAC_WITH_APDU_AT is NO LONGER MAINTAINED and maybe REMOVED in future releases.")
+
     function(add_at_driver target_name extra_sources)
         add_library(${target_name} SHARED
             ${CMAKE_CURRENT_SOURCE_DIR}/apdu/at_helpers.c

driver/apdu/at_etsi.c

@@ -137,6 +137,8 @@ static void apdu_interface_logic_channel_close(struct euicc_ctx *ctx, const uint
 }
 
 static int libapduinterface_init(struct euicc_apdu_interface *ifstruct) {
+    at_warning_message();
+
     set_deprecated_env_name(ENV_AT_DEBUG, "AT_DEBUG");
     set_deprecated_env_name(ENV_AT_DEVICE, "AT_DEVICE");
 

driver/apdu/at_etsi_csim.c

@@ -141,6 +141,8 @@ static void apdu_interface_logic_channel_close(struct euicc_ctx *ctx, const uint
 }
 
 static int libapduinterface_init(struct euicc_apdu_interface *ifstruct) {
+    at_warning_message();
+
     set_deprecated_env_name(ENV_AT_DEBUG, "AT_DEBUG");
     set_deprecated_env_name(ENV_AT_DEVICE, "AT_DEVICE");
 

driver/apdu/at_helpers.c

@@ -4,7 +4,22 @@
 #include <string.h>
 
 #include "at_helpers.h"
+
 #include <lpac/utils.h>
+#include <unistd.h>
+
+inline void at_warning_message(void) {
+    static char *message =
+        "WARNING: AT driver is for demo purposes only.\n"
+        "WARNING: AT driver strictly complies with \"ETSI TS 127 007\" specification.\n"
+        "WARNING: Some operations (e.g: download, delete, etc.), may fail due to insufficient response time.\n";
+
+    if (isatty(fileno(stdin))) {
+        fprintf(stderr, "\033[0;31m%s\033[0m", message);
+    } else {
+        fprintf(stderr, "%s", message);
+    }
+}
 
 char *at_channel_get(struct at_userdata *userdata, const int index) {
     if (index <= 0 || index > AT_MAX_LOGICAL_CHANNELS)

driver/apdu/at_helpers.h

@@ -2,6 +2,7 @@
 
 #include "at_cmd.h"
 
+void at_warning_message(void);
 char *at_channel_get(struct at_userdata *userdata, int index);
 int at_channel_set(struct at_userdata *userdata, int index, const char *identifier);
 int at_channel_next_id(struct at_userdata *userdata);