Only limit App partitions to 16MB, allow others to be bigger.

The bootloader will crash when starting from an app partition which exceeds
16MB, but larger sizes are fine for data partitions.

Fixes esp-rs#34

src/lib.rs

@@ -285,7 +285,7 @@ impl PartitionTable {
     pub fn validate(&self) -> Result<(), Error> {
         use self::partition::{APP_PARTITION_ALIGNMENT, DATA_PARTITION_ALIGNMENT};
 
-        const MAX_PART_SIZE: u32 = 0x100_0000; // 16MB
+        const MAX_APP_PART_SIZE: u32 = 0x100_0000; // 16MB
         const OTADATA_SIZE: u32 = 0x2000; // 8kB
 
         // There must be at least one partition with type 'app'
@@ -317,9 +317,9 @@ impl PartitionTable {
                 return Err(Error::UnalignedPartition);
             }
 
-            // Partitions cannot exceed 16MB; see:
+            // App partitions cannot exceed 16MB; see:
             // https://github.com/espressif/esp-idf/blob/c212305/components/bootloader_support/src/esp_image_format.c#L158-L161
-            if partition.size() > MAX_PART_SIZE {
+            if partition.ty() == Type::App && partition.size() > MAX_APP_PART_SIZE {
                 return Err(Error::PartitionTooLarge(partition.name()));
             }
         }