[Qemu-devel] Re: [RFC PATCH 00/15] Be able to compile out not needed options

[Juan Quintela]

Anthony Liguori <address@hidden> wrote:
> address@hidden wrote:
>> From: Juan Quintela <address@hidden>
>>
>> Hi
>>
>> this series of patches:
>> a- move object files only used by one target to that target Makefile.target
>> b- add flags to disable parts: --disable-{bluez,usb,vwmare,virtio,scsi}
>>    defaults is leave it enabled.  You need to add the --disable-* flag to 
>> get any change
>> c- disable the use of --smb <dir>
>>
>> What is the intent:  we want to be able to not compile-in things that we are 
>> not
>> interested in (they are experimental/not needed for our target/...).
>>
>> Is this the right approach?  Should I do something different?
>>
>> For the next series, I am also interested on enable/disabling bits of a 
>> subsysem:
>> being able to support usb-hid but not usb-{host,net,msnd}.  I already have 
>> patches
>> to disable that, just waiting to hear what is the preffered way to get
>> that functionality.
>>
>> Known problems:
>> - qemu-*.hx files don't run over cpp and then we are not able to remove from
>>   the help page the options that we don't support.
>> - drive_hot_add without scsi support do nothing.
>>
>> Any comments?
>>   
>
> To me, there are a few fundamental requirements for this:
>
> 1) This be configurable via a .config file instead of via ./configure
> options.

We have config-hosts.mak.
If we don't want to do it with ./configure, with what/how do you want it
to happen.

Do we agree in having:

qemu/.config
qemu/.config.mak
target-*/.config
target-*/.config.mak

And remove Makefile.target (i.e. split it in the target directories).

The problem that I saw otherwise with current approach is that it
is difficult to have a module linked for one target and not for another.
(No adding yet more ifdefs tricks is not a solution IMHO).

> 2) This involve no additional #ifdefs in the code

That is doable, if we agree that putting stub declarations in .h files
is ok.  I was following the "current style".

> 3) In the Makefiles, instead of having ifdef conditionals, we do:
>    objs-$(CONFIG_FOO) += foo.o

No problem with that for me if people agree in merging this solution.

> The block/ drivers are the model here.  If you drop individual files
> from the build, it Just Works.

But block/ drivers are _easy_ in this regard, you only have to register
a struct, and they become available.  USB/SCSI/... touch code in the
middle of pc.c and the other platforms "machine" files.

On the other hand, block implementation is not flexible enough for us
yet (TM).  We would like to be able to complie all block drivers for
qemu-img and only some of them for qemu :)

Will redo the patches with this (and the other people suggestions).

Thank for the input, Juan.

> Regards,
>
> Anthony Liguori