[Qemu-devel] Re: [PATCH 0/3] Remove ->bdrv_pread() internal block layer API

[Anthony Liguori <anthony@codemonkey.ws>]

Avi Kivity wrote:
> The internal block layer API has a wart in the form of the
> ->bdrv_pread() and ->bdrv_pwrite() methods.  These duplicate
> bdrv_read() and bdrv_write(), and are unnatural for a block
> device in that they are not sector oriented.
>
> One of the reasons for their existence is the scsi-generic host support.
> That is also a wart, as scsi-generic is really a packet (command/response)
> rather than a block (random access to sectors) API.  There is also the
> wierd negative sector count == byte count thing.
>   

Great stuff, this has always bugged me.

Regards,

Anthony Liguori

> This patchset addresses these warts by adding a new API for scsi-generic
> and dropping ->bdrv_pread() and bdrv_pwrite().  While the improvement
> falls short of spectacular, it does make further hacking on the block
> layer easier as there are fewer callbacks to worry about.
>
> Avi Kivity (3):
>   Add specialized block driver scsi generic API
>   Add internal scsi generic block API
>   Drop internal bdrv_pread()/bdrv_pwrite() APIs
>
>  block-raw-posix.c |   50 +++++++++++++++++++++++++--
>  block-raw-win32.c |   20 +++++++----
>  block.c           |   95 +++++++++++++++-------------------------------------
>  block.h           |    8 ++++
>  block_int.h       |   14 +++++--
>  hw/scsi-generic.c |   39 ++++++++++++---------
>  6 files changed, 126 insertions(+), 100 deletions(-)
>
>