On Thu, 30 Dec 2010 11:08:20 -0500 Douglas Gilbert wrote:
quoted text > Randy,
> Add some extra words to define what is expected if
> a transport can do out-of-order data delivery
> (e.g. FCP_RESID, theoretically, is not precisely
> the resid we want).
Can James use your previous:
quoted text >> Signed-off-by: Douglas Gilbert<dgilbert@interlog.com>
for this patch?
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Thanks.
quoted text > diff --git a/Documentation/scsi/scsi_mid_low_api.txt
> b/Documentation/scsi/scsi_mid_low_api.txt
> index df322c1..d998af0 100644
> --- a/Documentation/scsi/scsi_mid_low_api.txt
> +++ b/Documentation/scsi/scsi_mid_low_api.txt
> @@ -185,7 +185,7 @@ scsi_remove_host() ---------+
> scsi_host_put()
> ------------------------------------------------------------
>
> -It may be useful for a LLD to keep track of struct Scsi_Host instances
> +It may be useful for an LLD to keep track of struct Scsi_Host instances
> (a pointer is returned by scsi_host_alloc()). Such instances are "owned"
> by the mid-level. struct Scsi_Host instances are freed from
> scsi_host_put() when the reference count hits zero.
> @@ -749,7 +749,7 @@ void scsi_unblock_requests(struct Scsi_Host * shost)
> *
> * Notes: Should not be invoked if the "hotplug initialization
> * model" is being used. Called internally by exit_this_scsi_driver()
> - * in the "passive initialization model". Hence a LLD has no need to
> + * in the "passive initialization model". Hence an LLD has no need to
> * call this function directly.
> *
> * Defined in: drivers/scsi/hosts.c .
> @@ -1343,7 +1343,7 @@ Members of interest:
> underruns (overruns should be rare). If possible an LLD
> should set 'resid' prior to invoking 'done'. The most
> interesting case is data transfers from a SCSI target
> - device device (i.e. READs) that underrun.
> + device (e.g. READs) that underrun.
> underflow - LLD should place (DID_ERROR << 16) in 'result' if
> actual number of bytes transferred is less than this
> figure. Not many LLDs implement this check and some that
> @@ -1351,6 +1351,22 @@ Members of interest:
> report a DID_ERROR. Better for an LLD to implement
> 'resid'.
>
> +It is recommended that an LLD set 'resid' on data transfers from a SCSI
> +target device (e.g. READs). It is especially important that 'resid' is set
> +when such data transfers have sense keys of MEDIUM ERROR and HARDWARE ERROR
> +(and possibly RECOVERED ERROR). In these cases if an LLD is in doubt how much
> +data has been received then the safest approach is to indicate no bytes have
> +been received. For example: to indicate that no valid data has been received
> +an LLD might use these helpers:
> + scsi_set_resid(SCpnt, scsi_bufflen(SCpnt));
> +where 'SCpnt' is a pointer to a scsi_cmnd object. To indicate only three 512
> +bytes blocks has been received 'resid' could be set like this:
> + scsi_set_resid(SCpnt, scsi_bufflen(SCpnt) - (3 * 512));
> +
> +For transports that can do "out of order" delivery of data from a SCSI target
> +device, the 'resid' should reflect the number of valid, consecutive bytes
> +from the start of the buffer.
> +
> The scsi_cmnd structure is defined in include/scsi/scsi_cmnd.h
>
>
> Doug Gilbert
>
>
> On 10-12-24 12:46 PM, Randy Dunlap wrote:
> > On Thu, 23 Dec 2010 21:40:37 -0500 Douglas Gilbert wrote:
> >
> >> As discussed in a thread on this list titled:
> >> "RFC: short reads on block devices"
> >> this patch adds recommendations for LLDs to set resid
> >> when there might be uncertainty about how much data
> >> has been returned by a device.
> >>
> >> This patch inline and attached] is against scsi-misc-2.6.git
> >>
> >>
> >> Signed-off-by: Douglas Gilbert<dgilbert@interlog.com>
> >>
> >>
> >> diff --git a/Documentation/scsi/scsi_mid_low_api.txt
> >> b/Documentation/scsi/scsi_mid_low_api.txt
> >> index df322c1..7bcdea7 100644
> >> --- a/Documentation/scsi/scsi_mid_low_api.txt
> >> +++ b/Documentation/scsi/scsi_mid_low_api.txt
> >
> >> @@ -1351,6 +1351,18 @@ Members of interest:
> >> report a DID_ERROR. Better for an LLD to implement
> >> 'resid'.
> >>
> >> +It is recommended that a LLD set 'resid' on data transfers from a SCSI
> >> +target device (e.g. READs). It is especially important that 'resid' is set
> >> +when such data transfers have sense keys of MEDIUM ERROR and HARDWARE ERROR
> >> +(and possibly RECOVERED ERROR). In these cases if a LLD is in doubt how much
> >> +data has been received then the safest approach is to indicate no bytes have
> >> +been received. For example: to indicate that no valid data has been received
> >> +a LLD might use these helpers:
> >> + scsi_set_resid(SCpnt, scsi_bufflen(SCpnt));
> >> +where 'SCpnt' is a pointer to a scsi_cmnd object. To indicate only three 512
> >> +bytes blocks has been received 'resid' could be set like this:
> >> + scsi_set_resid(SCpnt, scsi_bufflen(SCpnt) - (3 * 512));
> >> +
> >> The scsi_cmnd structure is defined in include/scsi/scsi_cmnd.h
> >
> >
> > Hi Doug,
> >
> > Using "an LLD" instead of "a LLD" would be more consistent with the rest
> > of this txt file (and read better to me).
---
~Randy
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