On Wed, 24 Feb 2010, Ramya Desai wrote: > I did exactly. I removed the following statement from > store_max_sectors (drivers/usb/storage/scsiglue.c) function. > " && ms <= SCSI_DEFAULT_MAX_SECTORS". I also changed the .max_sectors > = 2048 in the host template. > > Then I restarted the system and build the usb-storage without any issue. > > After inserting my device, I found 1024 in > /sys/block/sdb/device/max_sectors. So, I tried to increase the value > through echo 2048 > /sys/block/sdb/device/max_sectors. When I do this, > it invoked the store_max_sectors() in the scsiglue.c file and able to > see ms (the variable in the store_max_sectors()) is 2048. But, the > value in the /sys/block/sdb/device/max_sectors is still 1024 only. That's right. Writing 2048 to that file sets max_hw_sectors to 2048 while leaving max_sectors set at 1024. The value displayed in the file is max_sectors -- it really ought to be max_hw_sectors. You can fix this by editing the show_max_sectors() function in scsiglue.c: change "queue_max_sectors" to "queue_max_hw_sectors". > When I looked into the /sys/block/sdb/queue/max_hw_sectors_kb, it > shows 1024, which is 2048 sectors. As it should be. > Then, I tried to increase the value > in /sys/block/sdb/queue/max_sectors_kb through echo 1024 > > /sys/block/sdb/queue/max_sectors_kb. After this, I saw 1024 in the > /sys/block/sdb/queue/max_sectors_kb. When I see 1024 in > /sys/block/sdb/queue/max_sectors_kb then I found 2048 in > /sys/block/sdb/device/max_sectors. Right, because that file displays max_sectors instead of max_hw_sectors. > However, this time, still my device > received 512 KB (1024) data transfer buffers in scsi_command. At this point everything was set up correctly. I don't know why the transfer lengths are still 512 KB. Maybe someone else has an idea. Alan Stern -- 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
