Re: [PATCH] Clarify the cases where BLKIF_RSP_EOPNOTSUPP can be returned.

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Aug 28, 2025 at 10:38:21AM +0100, Mark Syms wrote:
> Previously this said it would only happen on barrier writes. Except
> the documentation blocks for
>  * feature-flush-cache
>  * feature-discard
> 
> Also say that they can return this error.
> 
> Signed-off-by: Mark Syms <mark.syms@xxxxxxxxx>
> ---
>  xen/include/public/io/blkif.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/xen/include/public/io/blkif.h b/xen/include/public/io/blkif.h
> index 8407453324..5e617b0c67 100644
> --- a/xen/include/public/io/blkif.h
> +++ b/xen/include/public/io/blkif.h
> @@ -710,7 +710,7 @@ typedef struct blkif_response blkif_response_t;
>  /*
>   * STATUS RETURN CODES.
>   */
> - /* Operation not supported (only happens on barrier writes). */
> + /* Operation not supported, see feature-barrier, feature-flush-cache, 
> feature-discard. */
>  #define BLKIF_RSP_EOPNOTSUPP  -2

I think there's no need to mention the specific operations. FWIW,
blkback will return BLKIF_RSP_EOPNOTSUPP for any request type it
doesn't understand (see dispatch_other_io()), which covers any
possible request type that's not yet defined:

/* Operation not supported. */
#define BLKIF_RSP_EOPNOTSUPP  -2

Should be fine.

Thanks, Roger.