Re: [virtio-dev] [PATCH] virtio-blk: document VIRTIO_BLK_T_GET_ID

[Jan Kiszka <jan.kiszka@siemens.com>]

On 02.12.19 11:02, Stefan Hajnoczi wrote:
> The VIRTIO_BLK_T_GET_ID request type was implemented in Linux and QEMU
> in 2010.  It does not have a feature bit but devices respond with
> VIRTIO_BLK_S_UNSUPP if a request type is unimplemented.
>
> This patch documents the VIRTIO_BLK_T_GET_ID request type as currently
> implemented in Linux and QEMU.
>
> Suggested-by: Jan Kiszka <jan.kiszka@siemens.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>   content.tex | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/content.tex b/content.tex
> index d68cfaf..b8baaad 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -4094,12 +4094,14 @@ \subsection{Device Operation}\label{sec:Device Types / Block Device / Device Ope
>   
>   The type of the request is either a read (VIRTIO_BLK_T_IN), a write
>   (VIRTIO_BLK_T_OUT), a discard (VIRTIO_BLK_T_DISCARD), a write zeroes
> -(VIRTIO_BLK_T_WRITE_ZEROES) or a flush (VIRTIO_BLK_T_FLUSH).
> +(VIRTIO_BLK_T_WRITE_ZEROES), a flush (VIRTIO_BLK_T_FLUSH), or a get device ID
> +string command (VIRTIO_BLK_T_GET_ID).
>   
>   \begin{lstlisting}
>   #define VIRTIO_BLK_T_IN           0
>   #define VIRTIO_BLK_T_OUT          1
>   #define VIRTIO_BLK_T_FLUSH        4
> +#define VIRTIO_BLK_T_GET_ID       8
>   #define VIRTIO_BLK_T_DISCARD      11
>   #define VIRTIO_BLK_T_WRITE_ZEROES 13
>   \end{lstlisting}
> @@ -4135,6 +4137,10 @@ \subsection{Device Operation}\label{sec:Device Types / Block Device / Device Ope
>   the device to discard the specified range, provided that following reads return
>   zeroes.
>   
> +VIRTIO_BLK_T_GET_ID requests fetch the device ID string from the device into
> +\field{data}.  The device ID string is a NUL-padded ASCII string up to 20 bytes
> +long.  If the string is 20 bytes long then there is no NUL terminator.
> +
>   The final \field{status} byte is written by the device: either
>   VIRTIO_BLK_S_OK for success, VIRTIO_BLK_S_IOERR for device or driver
>   error or VIRTIO_BLK_S_UNSUPP for a request unsupported by device:
> @@ -4166,6 +4172,8 @@ \subsection{Device Operation}\label{sec:Device Types / Block Device / Device Ope
>   virtio_blk_discard_write_zeroes for VIRTIO_BLK_T_DISCARD and
>   VIRTIO_BLK_T_WRITE_ZEROES requests.
>   
> +The length of \field{data} MUST be 20 bytes for VIRTIO_BLK_T_GET_ID requests.
> +
>   VIRTIO_BLK_T_DISCARD requests MUST NOT contain more than
>   \field{max_discard_seg} struct virtio_blk_discard_write_zeroes segments in
>   \field{data}.

Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>

Thanks,
Jan

--
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