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When editing a mode page on a tape drive, do not clear the device

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specific parameter.

Tape drives include write protect (WP), Buffered Mode and Speed
settings in the device-specific parameter.  Clearing this
parameter on a mode select can have the effect of turning off
write protect or buffered mode, or changing the speed setting of
the tape drive.

Disks report DPO/FUA support via the device specific parameter
for MODE SENSE, but the bit is reserved for MODE SELECT.  So we
clear this for disks (and other non-tape devices) to avoid
potential errors from the target device.

sbin/camcontrol/modeedit.c:
	Clear the device-specific parameter in the mode page
	header if we're not operating on a tape drive.

MFC after:	3 days
Sponsored by:	Spectra Logic
This commit is contained in:
Kenneth D. Merry 2017-05-05 21:29:28 +00:00
parent 6790499792
commit 1e773aeb99
1 changed files with 14 additions and 1 deletions
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15
sbin/camcontrol/modeedit.c
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@ -629,8 +629,21 @@ editlist_save(struct cam_device *device, int dbd, int pc, int page,
/* Recalculate headers & offsets. */
mh->data_length = 0; /* Reserved for MODE SELECT command. */
mh->dev_spec = 0; /* Clear device-specific parameters. */
mh->blk_desc_len = 0; /* No block descriptors. */
/*
* Tape drives include write protect (WP), Buffered Mode and Speed
* settings in the device-specific parameter. Clearing this
* parameter on a mode select can have the effect of turning off
* write protect or buffered mode, or changing the speed setting of
* the tape drive.
*
* Disks report DPO/FUA support via the device specific parameter
* for MODE SENSE, but the bit is reserved for MODE SELECT. So we
* clear this for disks (and other non-tape devices) to avoid
* potential errors from the target device.
*/
if (device->pd_type != T_SEQUENTIAL)
mh->dev_spec = 0;
mph = MODE_PAGE_HEADER(mh);
mph->page_code &= ~SMPH_PS; /* Reserved for MODE SELECT command. */