http://bugzilla.kernel.org/show_bug.cgi?id=12207 --- Comment #28 from Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> 2009-04-10 15:19:23 --- On Fri, 10 Apr 2009 bugzilla-daemon@xxxxxxxxxxxxxxxxxxx wrote: > --- Comment #27 from oshida@xxxxxxxxxxx 2009-04-10 09:48:44 --- > Thanks for reading. > > Please share that this is just for tape device. Your patch affects the max_sectors attribute file for all devices, not just for tape devices. > > Where did your limit come from? > > Just above experiments. > But 4MB (or twiced 8MB) is not my recommend. For reguralizing I hope you to > decide which is reasonable value. > > Generally, there is no device which can operate the block size larger than > 0xffffff bytes. This is from the SCSI tape device specification. (T10/SSC) So there is no _tape_ device which can operate with larger block size. But maybe a non-tape device can. Besides, the block size isn't the same as max_sectors. max_sectors is allowed to be larger than the block size (but it mustn't be smaller). > > Why do you want to do this? The attribute is named "max_sectors", so > > shouldn't it return the value of max_sectors? > > I can agree your suggestion but then I need declaring the read only attribute > named "max_hw_sectors". Why? > I don't know the restrictions arround scsi driver stacks, ex, what max_sectors > is used for and max_hw_sectors is used for. But by simple image, if a really > effective value can be set onto a variable, it should be verifiable by reading > same variable. max_hw_sectors is supposed to be the largest transfer size supported by the hardware. max_sectors is supposed to be the largest transfer size the kernel will use. Therefore we should always have max_sectors <= max_hw_sectors. With USB mass-storage devices this is difficult, because the driver doesn't know what transfer sizes are supported by the hardware. The USB protocol doesn't provide this information. > > Did you know that max_sectors can also be changed through the block > > interface? > > I'm sorry I did not. Thanks for teaching. > But I could not find the device (of course tape drive) under that tree. I think > that is just for kinds of block device which can be manipulated with T10/SBC > command set. No, it is for all block devices. If you can't find your device under /sys/block/ then look for it somewhere else, such as under /sys/bus/scsi/devices/. Alan Stern -- Configure bugmail: http://bugzilla.kernel.org/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are the assignee for the bug. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
