[Qemu-devel] [PATCH 1/2] fw_cfg: add fw_cfg_modify_i16 (update) method

["Gabriel L. Somlo" <somlo@cmu.edu>]

Allow the ability to modify the value of an existing 16-bit integer
fw_cfg item.

Signed-off-by: Gabriel Somlo <somlo@cmu.edu>
---

Couple of thoughts:

   1. I'm thinking about pre-emptively creating _i16, _i32, and _i64
      versions, but right now (for fixing sparc and ppc) we only need
      the _i16 version. What to do ?

   2. Part of me wants to find the memory location containing the previous
      value and simply overwrite it, but I'll need to somehow ensure the
      blob being replaced was of the same size, etc., which could get hairy.
      So for now I'm going with the paranoid/safe version which allocates
      a new blob and frees the old one.

Thanks,
  Gabriel

 hw/nvram/fw_cfg.c         | 10 ++++++++++
 include/hw/nvram/fw_cfg.h |  1 +
 2 files changed, 11 insertions(+)

diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 68eff77..08b5cc3 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -484,6 +484,16 @@ void fw_cfg_add_i16(FWCfgState *s, uint16_t key, uint16_t value)
     fw_cfg_add_bytes(s, key, copy, sizeof(value));
 }
 
+void fw_cfg_modify_i16(FWCfgState *s, uint16_t key, uint16_t value)
+{
+    uint16_t *copy, *old;
+
+    copy = g_malloc(sizeof(value));
+    *copy = cpu_to_le16(value);
+    old = fw_cfg_modify_bytes_read(s, key, copy, sizeof(value));
+    g_free(old);
+}
+
 void fw_cfg_add_i32(FWCfgState *s, uint16_t key, uint32_t value)
 {
     uint32_t *copy;
diff --git a/include/hw/nvram/fw_cfg.h b/include/hw/nvram/fw_cfg.h
index 6d8a8ac..bc6c4a0 100644
--- a/include/hw/nvram/fw_cfg.h
+++ b/include/hw/nvram/fw_cfg.h
@@ -67,6 +67,7 @@ typedef void (*FWCfgReadCallback)(void *opaque, uint32_t offset);
 void fw_cfg_add_bytes(FWCfgState *s, uint16_t key, void *data, size_t len);
 void fw_cfg_add_string(FWCfgState *s, uint16_t key, const char *value);
 void fw_cfg_add_i16(FWCfgState *s, uint16_t key, uint16_t value);
+void fw_cfg_modify_i16(FWCfgState *s, uint16_t key, uint16_t value);
 void fw_cfg_add_i32(FWCfgState *s, uint16_t key, uint32_t value);
 void fw_cfg_add_i64(FWCfgState *s, uint16_t key, uint64_t value);
 void fw_cfg_add_callback(FWCfgState *s, uint16_t key, FWCfgCallback callback,
-- 
2.1.0