dracut: add support for one only module groups

This supports the case where only a single module from a group
will be put into the initramfs to keep initramfs sizes down where
firmware files are getting large.

The kernel will denote a group like this:

MODULE_FIRMWARE_GROUP_ONLY_ONE("ga106-gsp");
MODULE_FIRMWARE("nvidia/ga106/gsp/gsp-5258902.bin");
MODULE_FIRMWARE("nvidia/ga106/gsp/gsp-5303002.bin");
MODULE_FIRMWARE_GROUP_ONLY_ONE("ga106-gsp");

dracut will then scan this group and install at least one
of the modules between the brackets for that group.

The ordering is decided by the way modinfo is written which
is reversed from the order things are specified, so dracut
will pick the first entry in the group, which will be the
last entry the kernel module specifies.

The kernel driver will then handle whatever it ends up finding.

Signed-off-by: Dave Airlie <[email protected]>

src/install/dracut-install.c

@@ -1396,6 +1396,7 @@ static int install_firmware(struct kmod_module *mod)
         struct kmod_list *l = NULL;
         _cleanup_kmod_module_info_free_list_ struct kmod_list *list = NULL;
         int ret;
+        bool in_group_only_one = false, group_only_one_found = false;
 
         char **q;
 
@@ -1408,10 +1409,36 @@ static int install_firmware(struct kmod_module *mod)
                 const char *key = kmod_module_info_get_key(l);
                 const char *value = NULL;
 
-                if (!streq("firmware", key))
+                if (!streq("firmware", key) &&
+                    !streq("firmware_group_only_one", key))
                         continue;
 
                 value = kmod_module_info_get_value(l);
+
+                if (streq("firmware_group_only_one", key)) {
+			/*
+			 * firmware group only one, picks one firmware from the given group.
+			 * dracut will pick the first firmware it can find on the disk from
+			 * the modinfo section.
+			 * This section is written by the kernel in reverse order, so the
+			 * the kernel modules should add the preferred ones last, and that
+			 * will ensure dracut picks them first.
+			 */
+                        if (in_group_only_one) {
+                                in_group_only_one = false;
+                                if (!group_only_one_found)
+                                        log_info("Possible missing firmware for group %s for kernel module %s", value,
+                                                 kmod_module_get_name(mod));
+                        } else {
+                                in_group_only_one = true;
+                                group_only_one_found = false;
+                        }
+                        continue;
+                }
+
+                if (in_group_only_one && group_only_one_found)
+                        continue;
+
                 log_debug("Firmware %s", value);
                 ret = -1;
                 STRV_FOREACH(q, firmwaredirs) {
@@ -1428,16 +1455,20 @@ static int install_firmware(struct kmod_module *mod)
                                 for (i = 0; i < globbuf.gl_pathc; i++) {
                                         ret = install_firmware_fullpath(globbuf.gl_pathv[i]);
                                         if (ret != 0) {
-                                                log_info("Possible missing firmware %s for kernel module %s", value,
-                                                         kmod_module_get_name(mod));
-                                        }
+                                                if (!in_group_only_one)
+                                                        log_info("Possible missing firmware %s for kernel module %s", value,
+                                                                 kmod_module_get_name(mod));
+                                        } else if (in_group_only_one)
+                                                group_only_one_found = true;
                                 }
                         } else {
                                 ret = install_firmware_fullpath(fwpath);
                                 if (ret != 0) {
-                                        log_info("Possible missing firmware %s for kernel module %s", value,
-                                                 kmod_module_get_name(mod));
-                                }
+                                        if (!in_group_only_one)
+                                                log_info("Possible missing firmware %s for kernel module %s", value,
+                                                         kmod_module_get_name(mod));
+                                } else if (in_group_only_one)
+                                                group_only_one_found = true;
                         }
                 }
         }