Re: [Qemu-devel] [PATCH] Give detailed info when pcie downstream port init failed

[Cao jin <caoj.fnst@cn.fujitsu.com>]

On 11/27/2015 10:22 PM, Markus Armbruster wrote:
> Cao jin <caoj.fnst@cn.fujitsu.com> writes:
>
>> Hi, Markus
>>
>> On 11/24/2015 06:08 PM, Markus Armbruster wrote:
[...]
>>
>> and this will cover to output to the monitor, right?
>
> The device still implements the old PCIDeviceClass.init() instead of the
> new .realize().  All devices need to be converted to .realize().  You
> can help by converting this one.
>
> .init() reports errors with error_report() and returns 0 on success, -1
> on failure.
>
> .realize() passes errors to its callers via its errp argument.
>

After reading you commit 28b07e7, I am aware of this;) Thanks very much 
for your detailed explanation:) I was always curious about why there are 
2 function(.init() & .realize()) for initializing device, now I guess I 
get it: it has just .init() at first, because of error report issue, the 
.realize() is added to replace it, in order to pass the error above. Do 
I understand it right ?

If I understand it right, I see there are still devices initialization 
using .init() of DeviceClass & PCIDeviceClass, maybe I can help to 
convert some of these.

> Commit 28b07e7 can serve as example of how to convert a device to
> realize().  There are many more.  The ones I did usually have "Convert
> to realize()" in the commit message's first line.
>

> Regarding six error paths: I counted six places that return -1 directly
> or goto err or similar.  Your patch adds a suitable error message to one
> of them.  The other five need one, too.  You'll have to examine the
> called functions to find out whether they report anything.  If they do,
> they need to be first converted to pass an Error to their callers
> instead.
>

It seems I have a misunderstanding about the "6 error paths":-[ I 
thought "error path" is a "error *reporting path*", like: fprintf the 
msg to stderr is a path, while output it via QMP is also a path. Because 
I did`t touch the code about -chardev/-mon/-monitor/-qmp before, so I 
spent 2 days reading the code:)

Now I am cleared, Thanks you very much for the clarifying, Markus, I 
think this mistake won`t happen to me later;) And actually, I was 
already thinking add suitable error msg to each error path:)

> .
>

-- 
Yours Sincerely,

Cao Jin