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Re: [Qemu-devel] Re: [RFC][PATCH v5 01/21] Move code related to fd handl

From: Michael Roth
Subject: Re: [Qemu-devel] Re: [RFC][PATCH v5 01/21] Move code related to fd handlers into utility functions
Date: Tue, 07 Dec 2010 08:48:08 -0600
User-agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-US; rv: Gecko/20101027 Thunderbird/3.1.6

On 12/07/2010 07:31 AM, Jes Sorensen wrote:
On 12/03/10 19:03, Michael Roth wrote:
This allows us to implement an i/o loop outside of vl.c that can
interact with objects that use qemu_set_fd_handler()

Signed-off-by: Michael Roth<address@hidden>

This commit message really tells us nothing. Please be more specific
about what is in the commit.

Currently, in qemu, the virtagent client/server functionality is driven by vl.c:main_loop_wait(), which implements a select() loop that kicks off handlers registered for various FDs/events via qemu_set_fd_handler().

To share the code with the agent, qemu-va.c, I re-implemented this i/o loop to do same thing, along with vl.c:qemu_set_fd_handler*() and friends. It was big nasty copy/paste job and I think most of the reviewers agreed that the i/o loop code should be shared.

This commit moves the shared code into back-end utility functions that get called by vl.c:qemu_set_fd_handler()/qemu_process_fd_handlers() and friends for qemu, and by qemu-tools.c:qemu_set_fd_handler()/qemu_process_fd_handlers() for tools.

So now to interact with code that uses qemu_set_fd_handler() you can built a select() loop around these utility functions.

diff --git a/qemu-ioh.c b/qemu-ioh.c
new file mode 100644
index 0000000..cc71470
--- /dev/null
+++ b/qemu-ioh.c
@@ -0,0 +1,115 @@
+ * QEMU System Emulator
+ *
+ * Copyright (c) 2003-2008 Fabrice Bellard
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to 
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:

Is this moved or new code? If the former, fine, but if it is new code,
you might want to leave your own name on the (c). I presume at least
some of the changes are (c) 2010?

It's moved out from vl.c, nearly verbatim...

+/* XXX: fd_read_poll should be suppressed, but an API change is
+   necessary in the character devices to suppress fd_can_read(). */

XXX in the comment isn't really of much use. Please make it more
explicit, or put your name in if it is a statement you wish to make.

Even down to the comments :)

+int qemu_set_fd_handler3(void *ioh_record_list,
+                         int fd,
+                         IOCanReadHandler *fd_read_poll,
+                         IOHandler *fd_read,
+                         IOHandler *fd_write,
+                         void *opaque)

I am not happy with this addition of numbers to these functions, it
doesn't tell us why we have a 3 and how it differs from 2. If 3 is
really the backend for implementing 2, maybe it would be better to name
it __qemu_set_fd_handler2() and then have macros/wrappers calling into it.

That was the initial plan, but qemu_set_fd_handler2() is a back-end of sorts for qemu_set_fd_handler(), so I was just trying to be consistent with the naming. Personally I don't have any objections one way or the other.


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