On Feb 13, 9:40am, Douglas Gilbert wrote:
>
> Daniel,
> Does that driver take any account of Scsi_Cmnd::sc_data_direction_flag?
> All upper level drivers (including sg) in the lk 2.4 series set
> the corresponding Scsi_Request::sr_data_direction_flag .
>
> In the case of sg in lk 2.4, it supports 2 interfaces:
> - In the newer one (not yet used by cdrecord) the data
> direction flag is given explicitly. [There could be
> PCI bus problems if the app gets the direction wrong].
> - In the older interface the internal data direction flag
> is deduced from the sizes of the data buffers given.
> There is a slight ambiguity when the write (to device)
> buffer and the read (from device) buffer are both
> given; a read from device data direction flag is assumed.
> [BTW The SCSI_IOCTL_SEND_COMMAND ioctl() makes a similar
> deduction.]
>
> If cdrecord is sending a vendor specific command that
> writes data to the device, but sets the read buffer
> up as well and thus tricks the above logic, then we get
> cdrecord changed. Cdrecord has a library called libscg
> that interfaces to many OSes and the generic structures
> within libscg have a data direction flag.
>
> > The other drivers in question may or may not be able
> > to recover from the missing item in their tables, but the fact that
> > these tables are in the drivers at all implies that they work best if
> > the tables are correct.
>
> Data direction tables shouldn't be needed in lk 2.4 .
>
> Doug Gilbert
I was reading Documentation/scsi-generic.txt in 2.4.1. I didn't see
anything about direction in the "new sg_header". Is there something
newer?
| The new sg_header offered in this driver is:
| #define SG_MAX_SENSE 16
| struct sg_header
| {
| int pack_len; /* [o] reply_len (ie useless) ignored as input */
| int reply_len; /* [i] max length of expected reply (inc. sg_header) */
| int pack_id; /* [io] id number of packet (use ints >= 0) */
| int result; /* [o] 0==ok, else (+ve) Unix errno (best ignored) */
| unsigned int twelve_byte:1;
| /* [i] Force 12 byte command length for group 6 & 7 commands */
| unsigned int target_status:5; /* [o] scsi status from target */
| unsigned int host_status:8; /* [o] host status (see "DID" codes) */
| unsigned int driver_status:8; /* [o] driver status+suggestion */
|
| unsigned int other_flags:10; /* unused */
| unsigned char sense_buffer[SG_MAX_SENSE]; /* [o] Output in 3 cases:
| when target_status is CHECK_CONDITION or
| when target_status is COMMAND_TERMINATED or
| when (driver_status & DRIVER_SENSE) is true. */
| }; /* This structure is 36 bytes long on i386 */
thanks
jeremy
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