platform/x86: think-lmi: Add possible_values for ThinkStation

ThinkStation platforms don't support the API to return possible_values
but instead embed it in the settings string.

Try and extract this information and set the possible_values attribute
appropriately.

Fixes: a40cd7ef22 ("platform/x86: think-lmi: Add WMI interface support on Lenovo platforms")
Signed-off-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Link: https://lore.kernel.org/r/20230320003221.561750-4-mpearson-lenovo@squebb.ca
Reviewed-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/think-lmi.c

@@ -1450,6 +1450,26 @@ static int tlmi_analyze(void)
 			if (ret || !setting->possible_values)
 				pr_info("Error retrieving possible values for %d : %s\n",
 						i, setting->display_name);
+		} else {
+			/*
+			 * Older Thinkstations don't support the bios_selections API.
+			 * Instead they store this as a [Optional:Option1,Option2] section of the
+			 * name string.
+			 * Try and pull that out if it's available.
+			 */
+			char *item, *optstart, *optend;
+
+			if (!tlmi_setting(setting->index, &item, LENOVO_BIOS_SETTING_GUID)) {
+				optstart = strstr(item, "[Optional:");
+				if (optstart) {
+					optstart += strlen("[Optional:");
+					optend = strstr(optstart, "]");
+					if (optend)
+						setting->possible_values =
+							kstrndup(optstart, optend - optstart,
+									GFP_KERNEL);
+				}
+			}
 		}
 		/*
 		 * firmware-attributes requires that possible_values are separated by ';' but