dm: stdio: Allow lazy probing of video devices

At present all video devices are probed on start-up. It would be better to
probe a device only when it is needed. This can happen if it is referenced
in the stdout environment variable, for example.

Add support for this by searching for a suitable device when needed, probing
it, and finding the stdio device it creates.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

diff --git a/common/stdio.c b/common/stdio.c
index f99cfe7f4f0db6cf560dd0766cba3ab5224322da..ab9b05df48abb61c03d46f6e47ac845c8125a3e5 100644 (file)
--- a/common/stdio.c
+++ b/common/stdio.c
@@ -121,19 +121,87 @@ struct list_head* stdio_get_list(void)
        return &(devs.list);
 }
 
+#ifdef CONFIG_DM_VIDEO
+/**
+ * stdio_probe_device() - Find a device which provides the given stdio device
+ *
+ * This looks for a device of the given uclass which provides a particular
+ * stdio device. It is currently really only useful for UCLASS_VIDEO.
+ *
+ * Ultimately we want to be able to probe a device by its stdio name. At
+ * present devices register in their probe function (for video devices this
+ * is done in vidconsole_post_probe()) and we don't know what name they will
+ * use until they do so.
+ * TODO(sjg@chromium.org): We should be able to determine the name before
+ * probing, and probe the required device.
+ *
+ * @name:      stdio device name (e.g. "vidconsole")
+ * id:         Uclass ID of device to look for (e.g. UCLASS_VIDEO)
+ * @sdevp:     Returns stdout device, if found, else NULL
+ * @return 0 if found, -ENOENT if no device found with that name, other -ve
+ *        on other error
+ */
+static int stdio_probe_device(const char *name, enum uclass_id id,
+                             struct stdio_dev **sdevp)
+{
+       struct stdio_dev *sdev;
+       struct udevice *dev;
+       int seq, ret;
+
+       *sdevp = NULL;
+       seq = trailing_strtoln(name, NULL);
+       if (seq == -1)
+               ret = uclass_first_device_err(id, &dev);
+       else
+               ret = uclass_get_device_by_seq(id, seq, &dev);
+       if (ret) {
+               debug("No %s device for seq %d (%s)\n", uclass_get_name(id),
+                     seq, name);
+               return ret;
+       }
+       /* The device should be be the last one registered */
+       sdev = list_empty(&devs.list) ? NULL :
+                       list_last_entry(&devs.list, struct stdio_dev, list);
+       if (!sdev || strcmp(sdev->name, name)) {
+               debug("Device '%s' did not register with stdio as '%s'\n",
+                     dev->name, name);
+               return -ENOENT;
+       }
+       *sdevp = sdev;
+
+       return 0;
+}
+#endif
+
 struct stdio_dev* stdio_get_by_name(const char *name)
 {
        struct list_head *pos;
-       struct stdio_dev *dev;
+       struct stdio_dev *sdev;
 
        if(!name)
                return NULL;
 
        list_for_each(pos, &(devs.list)) {
-               dev = list_entry(pos, struct stdio_dev, list);
-               if(strcmp(dev->name, name) == 0)
-                       return dev;
+               sdev = list_entry(pos, struct stdio_dev, list);
+               if (strcmp(sdev->name, name) == 0)
+                       return sdev;
        }
+#ifdef CONFIG_DM_VIDEO
+       /*
+        * We did not find a suitable stdio device. If there is a video
+        * driver with a name starting with 'vidconsole', we can try probing
+        * that in the hope that it will produce the required stdio device.
+        *
+        * This function is sometimes called with the entire value of
+        * 'stdout', which may include a list of devices separate by commas.
+        * Obviously this is not going to work, so we ignore that case. The
+        * call path in that case is console_init_r() -> search_device() ->
+        * stdio_get_by_name().
+        */
+       if (!strncmp(name, "vidconsole", 10) && !strchr(name, ',') &&
+           !stdio_probe_device(name, UCLASS_VIDEO, &sdev))
+               return sdev;
+#endif
 
        return NULL;
 }
@@ -282,6 +350,16 @@ int stdio_add_devices(void)
 #endif
 #endif
 #ifdef CONFIG_DM_VIDEO
+       /*
+        * If the console setting is not in environment variables then
+        * console_init_r() will not be calling iomux_doenv() (which calls
+        * search_device()). So we will not dynamically add devices by
+        * calling stdio_probe_device().
+        *
+        * So just probe all video devices now so that whichever one is
+        * required will be available.
+        */
+#ifndef CONFIG_SYS_CONSOLE_IS_IN_ENV
        struct udevice *vdev;
 # ifndef CONFIG_DM_KEYBOARD
        int ret;
@@ -293,6 +371,7 @@ int stdio_add_devices(void)
                ;
        if (ret)
                printf("%s: Video device failed (ret=%d)\n", __func__, ret);
+#endif /* !CONFIG_SYS_CONSOLE_IS_IN_ENV */
 #else
 # if defined(CONFIG_LCD)
        drv_lcd_init ();