[Qemu-devel] [PATCH v2 1/2] fw_cfg: document fw_cfg_modify_iXX() update functions

[Gabriel L. Somlo]

Document the behavior of fw_cfg_modify_iXX() for leak-free update
of integer fw_cfg blobs; this function was added as a bug fix with
commit 48779e501810c5046ff8af7b9cf9c99bec2928a1.

Currently only fw_cfg_modify_i16() is coded, but 32- and 64-bit
versions may be added later if necessary.

Signed-off-by: Gabriel Somlo <address@hidden>
---
 docs/specs/fw_cfg.txt | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/docs/specs/fw_cfg.txt b/docs/specs/fw_cfg.txt
index 74351dd..5bc7b96 100644
--- a/docs/specs/fw_cfg.txt
+++ b/docs/specs/fw_cfg.txt
@@ -159,6 +159,17 @@ will convert a 16-, 32-, or 64-bit integer to 
little-endian, then add
 a dynamically allocated copy of the appropriately sized item to fw_cfg
 under the given selector key value.
 
+== fw_cfg_modify_iXX() ==
+
+Modify the value of an XX-bit item (where XX may be 16, 32, or 64).
+Similarly to the corresponding fw_cfg_add_iXX() function set, convert
+a 16-, 32-, or 64-bit integer to little endian, create a dynamically
+allocated copy of the required size, and replace the existing item at
+the given selector key value with the newly allocated one. The previous
+item, assumed to have been allocated during an earlier call to
+fw_cfg_add_iXX() or fw_cfg_modify_iXX() (of the same width XX), is freed
+before the function returns.
+
 == fw_cfg_add_file() ==
 
 Given a filename (i.e., fw_cfg item name), starting pointer, and size,
-- 
2.1.0