Re: [PATCH] libata: add support for ATA_16 commands to ATAPI devices

[Jeff Garzik <jeff@garzik.org>]

Mark Lord wrote:
> This patch adds support for passing ATA_16 commands
> through to ATAPI devices in libata.  In practice, the upper layers will
> still currently prevent ATA_16 commands, as no (?) ATAPI drives support
> them yet.  But it will work if such a drive is ever encountered.
> 
> Support for ATA_16 is necessary for using SG_IO from userspace,
> and an upcoming hdparm release will be updated to use this interface.
> 
> This version is very similar to the earlier first submission,
> except that ATA_12 is no longer passed through to ATAPI
> because of the conflict it has with the SCSI BLANK opcode.
> 
> Signed-off-by:  Mark Lord <mlord@pobox.com>
> 
> --- old/drivers/ata/libata-scsi.c	2007-01-02 19:20:23.000000000 -0500
> +++ new/drivers/ata/libata-scsi.c	2007-01-02 19:20:49.000000000 -0500
> @@ -2650,6 +2650,12 @@
>  
>  static inline ata_xlat_func_t ata_get_xlat_func(struct ata_device *dev, u8 cmd)
>  {
> +	if (cmd == ATA_16)
> +		return ata_scsi_pass_thru;
> +
> +	if (dev->class == ATA_DEV_ATAPI)
> +		return atapi_xlat;
> +

As I said, provide some avenue for the user to choose.

I do not wish to completely eliminate the current behavior, which passes 
through all opcodes to the ATAPI device.  You cannot guarantee that 
ATA_16 is never used for a vendor-reserved opcode, for example.

Your proposed change to the default behavior is ACK'd, as long as the 
current behavior is not completely eliminated, as you have done above.

	Jeff