add skeleton for BSD licensed "raw" BlockDriver

On 08/05/13 15:03, Paolo Bonzini wrote:
>
>
> ----- Original Message -----
>> From: "Laszlo Ersek" <lersek@redhat.com>
>> To: "Paolo Bonzini" <pbonzini@redhat.com>
>> Sent: Monday, August 5, 2013 2:43:46 PM
>> Subject: Re: [PATCH 1/2] raw: add license header
>>
>> On 08/02/13 00:27, Paolo Bonzini wrote:
>>> On 08/01/2013 10:13 AM, Christoph Hellwig wrote:
>>>> On Wed, Jul 31, 2013 at 08:19:51AM +0200, Paolo Bonzini wrote:
>>>>> Most of the block layer is under the BSD license, thus it is
>>>>> reasonable to license block/raw.c the same way.  CCed people should
>>>>> ACK by replying with a Signed-off-by line.
>>>>
>>>> The coded was intended to be GPLv2.
>>>
>>> Laszlo, would you be willing to do clean-room reverse engineering?
>>>
>>> (No rants, please. :))
>>
>> What's the scope exactly?
>
> It's quite small, it's a file full of forwarders like
>
> static void raw_foo(BlockDriverState *bs)
> {
>     return bdrv_foo(bs->file);
> }
>
> It's 170 lines of code, all as boring as this.  I only picked you
> because I'm quite certain you have never seen the file (and the answer
> confirmed it).
>
> Basically:
>
> 1) BlockDriver is a struct in which these function members are
> interesting:
>
>     .bdrv_reopen_prepare
>     .bdrv_co_readv
>     .bdrv_co_writev
>     .bdrv_co_is_allocated
>     .bdrv_co_write_zeroes
>     .bdrv_co_discard
>     .bdrv_getlength
>     .bdrv_get_info
>     .bdrv_truncate
>     .bdrv_is_inserted
>     .bdrv_media_changed
>     .bdrv_eject
>     .bdrv_lock_medium
>     .bdrv_ioctl
>     .bdrv_aio_ioctl
>     .bdrv_has_zero_init
>
> They should be implemented as simple forwarders (see above).
> There are 16 functions listed here, you can easily see how this
> already accounts for 100+ SLOC roughly...
>
> The implementations of bdrv_co_readv and bdrv_co_writev should also
> call BLKDBG_EVENT on bs->file too, before forwarding to bs->file.  The
> events to be generated are BLKDBG_READ_AIO and BLKDBG_WRITE_AIO.
>
> 2) This is also a simple forwarder function:
>
>     .bdrv_create
>
> but there is no BlockDriverState argument so the forwarded-to function
> does not have a bs->file argument either.  The forwarded-to function
> is bdrv_create_file.
>
> 3) These members are special
>
>     .format_name   is the string "raw"
>     .bdrv_open     raw_open should set bs->sg to bs->file->sg and return 0
>     .bdrv_close    raw_close should do nothing
>     .bdrv_probe    raw_probe should just return 1.
>
> 4) There is another member, .create_options, which is an array of
> QEMUOptionParameter structs, terminated by an all-zero item.  The only
> option you need is for the virtual disk size.  You will find something
> to copy from in other block drivers, for example block/qcow2.c.
>
> 5) Formats are registered with bdrv_register (takes a BlockDriver*).
> You also need to pass the caller of bdrv_register to block_init.
>
> 6) I'm not sure how to organize the patch series, so I'll leave this to
> your creativity.  I guess in this case move/copy detection of git should
> be disabled.  I would definitely include this spec in the commit
> message as a proof of clean-room reverse engineering.
>
> 7) Remember a BSD header like the one in block.c.
>
> Paolo

This patch implements the email up to the paragraph ending with "100+ SLOC
roughly". The skeleton is generated from the list there, with a simple
shell loop using "sed" and the raw_foo() template.

The BSD license block is copied (and reflowed) from
"util/qemu-progress.c".

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
