[PATCH 4/6] fastboot: only populate variables explicitly asked for

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

To allow flashing an image with a partition table followed by an image
for a specific partition, the fastboot implementation was changed to
evaluate partitions on demand.

As there are partition-specific variables and the magic "all" variable,
which lists all variables, all partitions are evaluated in getvar
unconditionally, when only a variable for a specific partition is needed.

When one partition doesn't exist and is not marked as optional, this
leads to an error, even if something innocuous as the general
max-download-size is requested.

Change this, so only partitions that were explicitly asked for have their
variables populated on demand, unless "all" variables were requested.

Fixes: 6a191155be4e ("fastboot: evaluate fastboot partitions when used")
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 common/fastboot.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/common/fastboot.c b/common/fastboot.c
index 231f49c1a6c9..529d9690db79 100644
--- a/common/fastboot.c
+++ b/common/fastboot.c
@@ -310,10 +310,15 @@ static void cb_getvar(struct fastboot *fb, const char *cmd)
 {
 	LIST_HEAD(partition_list);
 	struct file_list_entry *fentry;
+	const char *partition;
 	bool all;
 
 	pr_debug("getvar: \"%s\"\n", cmd);
 
+	partition = strchr(cmd, ':');
+	if (partition)
+		partition++;
+
 	all = !strcmp(cmd, "all");
 	if (all)
 		cmd = NULL;
@@ -321,9 +326,15 @@ static void cb_getvar(struct fastboot *fb, const char *cmd)
 	if (fastboot_tx_print_var(fb, &fb->variables, cmd))
 		goto out;
 
+	if (!all && !partition)
+		goto skip_partitions;
+
 	file_list_for_each_entry(fb->files, fentry) {
 		int ret;
 
+		if (!all && strcmp(partition, fentry->name))
+			continue;
+
 		ret = fastboot_add_partition_variables(fb, &partition_list, fentry);
 		if (ret) {
 			char *msg = xasprintf("%s: Failed to add '%s' partition variables: %pe",
@@ -338,6 +349,7 @@ static void cb_getvar(struct fastboot *fb, const char *cmd)
 	if (fastboot_tx_print_var(fb, &partition_list, cmd))
 		goto out;
 
+skip_partitions:
 	fastboot_tx_print(fb, FASTBOOT_MSG_OKAY, "");
 out:
 	fastboot_free_variables(&partition_list);
-- 
2.39.5