greybus: embed message buffer into message structure

Embed the buffer for message data into the message structure itself.
This allows us to use a single allocation for each message, and
more importantly will allow us to derive the message structure
describing a message from the buffer itself.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

diff --git a/drivers/staging/greybus/operation.c b/drivers/staging/greybus/operation.c
index b02c531..c9988fd 100644 (file)
--- a/drivers/staging/greybus/operation.c
+++ b/drivers/staging/greybus/operation.c
@@ -229,27 +229,6 @@ static void operation_timeout(struct work_struct *work)
        gb_operation_complete(operation);
 }
 
-static void *
-gb_buffer_alloc(struct greybus_host_device *hd, size_t size, gfp_t gfp_flags)
-{
-       u8 *buffer;
-
-       buffer = kzalloc(hd->buffer_headroom + size, gfp_flags);
-       if (buffer)
-               buffer += hd->buffer_headroom;
-
-       return buffer;
-}
-
-static void
-gb_buffer_free(struct greybus_host_device *hd, void *buffer)
-{
-       u8 *allocated = buffer;
-
-       if (allocated)
-               kfree(allocated - hd->buffer_headroom);
-}
-
 /*
  * Allocate a message to be used for an operation request or
  * response.  For outgoing messages, both types of message contain a
@@ -257,46 +236,47 @@ gb_buffer_free(struct greybus_host_device *hd, void *buffer)
  * responses also contain the same header, but there's no need to
  * initialize it here (it'll be overwritten by the incoming
  * message).
+ *
+ * Our message structure consists of:
+ *     message structure
+ *     headroom
+ *     message header  \_ these combined are
+ *     message payload /  the message size
  */
 static struct gb_message *
 gb_operation_message_alloc(struct greybus_host_device *hd, u8 type,
-                               size_t size, gfp_t gfp_flags)
+                               size_t payload_size, gfp_t gfp_flags)
 {
        struct gb_message *message;
        struct gb_operation_msg_hdr *header;
+       size_t message_size = payload_size + sizeof(*header);
+       size_t size;
+       u8 *buffer;
 
-       size += sizeof(*header);
-       if (size > hd->buffer_size_max)
+       if (message_size > hd->buffer_size_max)
                return NULL;
 
-       message = kzalloc(sizeof(*message), gfp_flags);
+       size = sizeof(*message) + hd->buffer_headroom + message_size;
+       message = kzalloc(size, gfp_flags);
        if (!message)
                return NULL;
-
-       header = gb_buffer_alloc(hd, size, gfp_flags);
-       if (!header) {
-               kfree(message);
-               return NULL;
-       }
+       buffer = &message->buffer[0];
+       header = (struct gb_operation_msg_hdr *)(buffer + hd->buffer_headroom);
 
        /* Fill in the header structure */
-       header->size = cpu_to_le16(size);
+       header->size = cpu_to_le16(message_size);
        header->operation_id = 0;       /* Filled in when submitted */
        header->type = type;
 
        message->header = header;
        message->payload = header + 1;
-       message->size = size;
+       message->size = message_size;
 
        return message;
 }
 
 static void gb_operation_message_free(struct gb_message *message)
 {
-       struct greybus_host_device *hd;
-
-       hd = message->operation->connection->hd;
-       gb_buffer_free(hd, message->header);
        kfree(message);
 }
 

diff --git a/drivers/staging/greybus/operation.h b/drivers/staging/greybus/operation.h
index 567bb70..2fdb41c 100644 (file)
--- a/drivers/staging/greybus/operation.h
+++ b/drivers/staging/greybus/operation.h
@@ -31,6 +31,8 @@ struct gb_message {
        struct gb_operation             *operation;
 
        void                            *cookie;
+
+       u8                              buffer[];
 };
 
 /*