core: new 'rpmsg' subsystem

Most older Qualcomm SoCs (e.g. MSM8916, MSM8974, ...) communicate with
the integrated modem via shared memory (SMD channels). This is similar
to QRTR on newer SoCs, but without the "network" layer. In fact, the
older SoCs also have QRTR, but the modem QMI services are not exposed
there.

The mainline Linux kernel exposes SMD channels via the "remote processor
messaging bus" (rpmsg). Through special IOCTL calls it is possible to
create a char device for a rpmsg/SMD channel. We can then use these to
send QMI/AT messages to the modem, much like the ordinary serial char
devices when using a Qualcomm modem through USB.

This commit introduces support for the new 'rpmsg' subsystem, which
allows exporting QMI-capable and AT-capable ports.

By default NO rpmsg port is flagged as candidate, it is assumed that
the plugin adding support for the rpmsg subsystem will add specific
rules to do so (e.g. so that non-modem ports are explicitly not
flagged as candidate).

All rpmsg ports will be probed for AT or QMI capabilities, unless
explicit port type hints (e.g. ID_MM_PORT_TYPE_QMI or
ID_MM_PORT_TYPE_AT_PRIMARY) are set.

These changes are highly based on the initial integration work done by
Stephan Gerhold <stephan@gerhold.net> in postmarketOS, see:
  https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/merge_requests/363

7 files changed, 62 insertions, 23 deletions

diff --git a/cli/mmcli-manager.c b/cli/mmcli-manager.c
index 950617b6..01d2972c 100644
--- a/cli/mmcli-manager.c
+++ b/cli/mmcli-manager.c
@@ -444,7 +444,7 @@ get_manager_ready (GObject      *source,
 
 #if defined WITH_UDEV
     if (report_kernel_event_auto_scan) {
-        const gchar *subsys[] = { "tty", "usbmisc", "net", NULL };
+        const gchar *subsys[] = { "tty", "usbmisc", "net", "rpmsg", NULL };
         guint i;
 
         ctx->udev = g_udev_client_new (subsys);
diff --git a/src/mm-base-modem.c b/src/mm-base-modem.c
index 09227da5..29256f7d 100644
--- a/src/mm-base-modem.c
+++ b/src/mm-base-modem.c
@@ -238,6 +238,20 @@ base_modem_create_usbmisc_port (MMBaseModem *self,
 }
 
 static MMPort *
+base_modem_create_rpmsg_port (MMBaseModem *self,
+                              const gchar *name,
+                              MMPortType   ptype)
+{
+#if defined WITH_QMI
+    if (ptype == MM_PORT_TYPE_QMI)
+        return MM_PORT (mm_port_qmi_new (name, MM_PORT_SUBSYS_RPMSG));
+#endif
+    if (ptype == MM_PORT_TYPE_AT)
+        return MM_PORT (mm_port_serial_at_new (name, MM_PORT_SUBSYS_RPMSG));
+    return NULL;
+}
+
+static MMPort *
 base_modem_create_virtual_port (MMBaseModem *self,
                                 const gchar *name)
 {
@@ -278,6 +292,8 @@ mm_base_modem_grab_port (MMBaseModem         *self,
         port = base_modem_create_tty_port (self, name, kernel_device, ptype);
     else if (g_str_equal (subsys, "usbmisc"))
         port = base_modem_create_usbmisc_port (self, name, ptype);
+    else if (g_str_equal (subsys, "rpmsg"))
+        port = base_modem_create_rpmsg_port (self, name, ptype);
     else if (g_str_equal (subsys, "virtual"))
         port = base_modem_create_virtual_port (self, name);
 
@@ -327,8 +343,6 @@ mm_base_modem_grab_port (MMBaseModem         *self,
     return TRUE;
 }
 
-/******************************************************************************/
-
 gboolean
 mm_base_modem_disable_finish (MMBaseModem   *self,
                               GAsyncResult  *res,
diff --git a/src/mm-filter.c b/src/mm-filter.c
index c5a15312..52575a1c 100644
--- a/src/mm-filter.c
+++ b/src/mm-filter.c
@@ -199,6 +199,13 @@ mm_filter_port (MMFilter        *self,
         return TRUE;
     }
 
+    /* If this is a rpmsg channel device, we always allow it */
+    if ((self->priv->enabled_rules & MM_FILTER_RULE_RPMSG) &&
+        (g_strcmp0 (subsystem, "rpmsg") == 0)) {
+        mm_obj_dbg (self, "(%s/%s) port allowed: rpmsg device", subsystem, name);
+        return TRUE;
+    }
+
     /* If this is a tty device, we may allow it */
     if ((self->priv->enabled_rules & MM_FILTER_RULE_TTY) &&
         (g_strcmp0 (subsystem, "tty") == 0)) {
diff --git a/src/mm-filter.h b/src/mm-filter.h
index dc5f2bff..8d2e0e22 100644
--- a/src/mm-filter.h
+++ b/src/mm-filter.h
@@ -53,15 +53,16 @@ typedef enum { /*< underscore_name=mm_filter_rule >*/
     MM_FILTER_RULE_VIRTUAL               = 1 << 3,
     MM_FILTER_RULE_NET                   = 1 << 4,
     MM_FILTER_RULE_USBMISC               = 1 << 5,
-    MM_FILTER_RULE_TTY                   = 1 << 6,
-    MM_FILTER_RULE_TTY_BLACKLIST         = 1 << 7,
-    MM_FILTER_RULE_TTY_MANUAL_SCAN_ONLY  = 1 << 8,
-    MM_FILTER_RULE_TTY_PLATFORM_DRIVER   = 1 << 9,
-    MM_FILTER_RULE_TTY_DEFAULT_ALLOWED   = 1 << 10,
-    MM_FILTER_RULE_TTY_DRIVER            = 1 << 11,
-    MM_FILTER_RULE_TTY_ACM_INTERFACE     = 1 << 12,
-    MM_FILTER_RULE_TTY_WITH_NET          = 1 << 13,
-    MM_FILTER_RULE_TTY_DEFAULT_FORBIDDEN = 1 << 14,
+    MM_FILTER_RULE_RPMSG                 = 1 << 6,
+    MM_FILTER_RULE_TTY                   = 1 << 7,
+    MM_FILTER_RULE_TTY_BLACKLIST         = 1 << 8,
+    MM_FILTER_RULE_TTY_MANUAL_SCAN_ONLY  = 1 << 9,
+    MM_FILTER_RULE_TTY_PLATFORM_DRIVER   = 1 << 10,
+    MM_FILTER_RULE_TTY_DEFAULT_ALLOWED   = 1 << 11,
+    MM_FILTER_RULE_TTY_DRIVER            = 1 << 12,
+    MM_FILTER_RULE_TTY_ACM_INTERFACE     = 1 << 13,
+    MM_FILTER_RULE_TTY_WITH_NET          = 1 << 14,
+    MM_FILTER_RULE_TTY_DEFAULT_FORBIDDEN = 1 << 15,
 } MMFilterRule;
 
 #define MM_FILTER_RULE_ALL                  \
@@ -71,6 +72,7 @@ typedef enum { /*< underscore_name=mm_filter_rule >*/
      MM_FILTER_RULE_VIRTUAL               | \
      MM_FILTER_RULE_NET                   | \
      MM_FILTER_RULE_USBMISC               | \
+     MM_FILTER_RULE_RPMSG                 | \
      MM_FILTER_RULE_TTY                   | \
      MM_FILTER_RULE_TTY_BLACKLIST         | \
      MM_FILTER_RULE_TTY_MANUAL_SCAN_ONLY  | \
@@ -89,6 +91,7 @@ typedef enum { /*< underscore_name=mm_filter_rule >*/
      MM_FILTER_RULE_VIRTUAL              | \
      MM_FILTER_RULE_NET                  | \
      MM_FILTER_RULE_USBMISC              | \
+     MM_FILTER_RULE_RPMSG                | \
      MM_FILTER_RULE_TTY                  | \
      MM_FILTER_RULE_TTY_BLACKLIST        | \
      MM_FILTER_RULE_TTY_MANUAL_SCAN_ONLY | \
@@ -104,6 +107,7 @@ typedef enum { /*< underscore_name=mm_filter_rule >*/
      MM_FILTER_RULE_VIRTUAL               | \
      MM_FILTER_RULE_NET                   | \
      MM_FILTER_RULE_USBMISC               | \
+     MM_FILTER_RULE_RPMSG                 | \
      MM_FILTER_RULE_TTY                   | \
      MM_FILTER_RULE_TTY_PLATFORM_DRIVER   | \
      MM_FILTER_RULE_TTY_DRIVER            | \
@@ -120,6 +124,7 @@ typedef enum { /*< underscore_name=mm_filter_rule >*/
      MM_FILTER_RULE_VIRTUAL               | \
      MM_FILTER_RULE_NET                   | \
      MM_FILTER_RULE_USBMISC               | \
+     MM_FILTER_RULE_RPMSG                 | \
      MM_FILTER_RULE_TTY                   | \
      MM_FILTER_RULE_TTY_BLACKLIST         | \
      MM_FILTER_RULE_TTY_MANUAL_SCAN_ONLY  | \
diff --git a/src/mm-plugin.c b/src/mm-plugin.c
index be6e39ff..13b46a75 100644
--- a/src/mm-plugin.c
+++ b/src/mm-plugin.c
@@ -781,6 +781,11 @@ mm_plugin_supports_port (MMPlugin            *self,
             probe_run_flags |= MM_PORT_PROBE_MBIM;
         else
             probe_run_flags |= MM_PORT_PROBE_AT;
+    } else if (g_str_equal (mm_kernel_device_get_subsystem (port), "rpmsg")) {
+        if (self->priv->at)
+            probe_run_flags |= MM_PORT_PROBE_AT;
+        if (self->priv->qmi)
+            probe_run_flags |= MM_PORT_PROBE_QMI;
     }
 
     /* For potential AT ports, check for more things */
diff --git a/src/mm-port-probe.c b/src/mm-port-probe.c
index c6b535b5..d4bffb3e 100644
--- a/src/mm-port-probe.c
+++ b/src/mm-port-probe.c
@@ -491,16 +491,22 @@ wdm_probe_qmi (MMPortProbe *self)
     ctx = g_task_get_task_data (self->priv->task);
 
 #if defined WITH_QMI
-    mm_obj_dbg (self, "probing QMI...");
+    {
+        MMPortSubsys subsys = MM_PORT_SUBSYS_USBMISC;
 
-    /* Create a port and try to open it */
-    ctx->port_qmi = mm_port_qmi_new (mm_kernel_device_get_name (self->priv->port),
-                                     MM_PORT_SUBSYS_USBMISC);
-    mm_port_qmi_open (ctx->port_qmi,
-                      FALSE,
-                      NULL,
-                      (GAsyncReadyCallback) port_qmi_open_ready,
-                      self);
+        mm_obj_dbg (self, "probing QMI...");
+
+        if (g_str_equal (mm_kernel_device_get_subsystem (self->priv->port), "rpmsg"))
+            subsys = MM_PORT_SUBSYS_RPMSG;
+
+        /* Create a port and try to open it */
+        ctx->port_qmi = mm_port_qmi_new (mm_kernel_device_get_name (self->priv->port), subsys);
+        mm_port_qmi_open (ctx->port_qmi,
+                          FALSE,
+                          NULL,
+                          (GAsyncReadyCallback) port_qmi_open_ready,
+                          self);
+    }
 #else
     /* If not compiled with QMI support, just assume we won't have any QMI port */
     mm_port_probe_set_result_qmi (self, FALSE);
@@ -1273,6 +1279,8 @@ serial_open_at (MMPortProbe *self)
 
         if (g_str_equal (mm_kernel_device_get_subsystem (self->priv->port), "usbmisc"))
             subsys = MM_PORT_SUBSYS_USBMISC;
+        else if (g_str_equal (mm_kernel_device_get_subsystem (self->priv->port), "rpmsg"))
+            subsys = MM_PORT_SUBSYS_RPMSG;
 
         ctx->serial = MM_PORT_SERIAL (mm_port_serial_at_new (mm_kernel_device_get_name (self->priv->port), subsys));
         if (!ctx->serial) {
diff --git a/src/mm-port.h b/src/mm-port.h
index 2d8d1ad6..8295d264 100644
--- a/src/mm-port.h
+++ b/src/mm-port.h
@@ -28,8 +28,8 @@ typedef enum { /*< underscore_name=mm_port_subsys >*/
     MM_PORT_SUBSYS_NET,
     MM_PORT_SUBSYS_USBMISC,
     MM_PORT_SUBSYS_UNIX,
-
-    MM_PORT_SUBSYS_LAST = MM_PORT_SUBSYS_UNIX /*< skip >*/
+    MM_PORT_SUBSYS_RPMSG,
+    MM_PORT_SUBSYS_LAST = MM_PORT_SUBSYS_RPMSG /*< skip >*/
 } MMPortSubsys;
 
 typedef enum { /*< underscore_name=mm_port_type >*/