On Tue, 2011-10-11 at 13:56 +0530, Amit Sahrawat wrote: > SCSI: Retrieve Cache Mode Using SG_ATA_16 if normal routine fails > > It has been observed that a number of USB HDD's do not respond correctly > to SCSI mode sense command(retrieve caching pages) which results in their > Write Cache being discarded by queue requests i.e., WCE if left set to > '0'(disabled). So, in order to identify the devices correctly - give it > a last try using SG_ATA_16 after failure from normal routine. This is a non-starter, as I've said before. Apart from the layering violation of trying to make sd ATA aware, ATA_16 is known to crash some USB devices (the bug reports are mostly about smartctl which can be made to use ATA_16 failing). The correct way to implement this is to have a user visible WCE variable that can be written to in the scsi_disk class sysfs files so the user can alter the caching type on the fly. James -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
