On Tue, Feb 23, 2010 at 11:31 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: Dear Alan, Thanks a lot. > So Ramya, it looks like you need to edit store_max_sectors() in > drivers/usb/storage/scsiglue.c. Get rid of the " && ms <= > SCSI_DEFAULT_MAX_SECTORS" part. > > Then you should be able to write a large value to > /sys/block/sdX/device/max_sectors to increase the hardware limit. The > new value divided by 2 will show up in > /sys/block/sdX/queue/max_hw_sectors_kb. > > Once that limit is increased, you can write a large value to > /sys/block/sdX/queue/max_sectors_kb. That should give you long > transfer lengths. 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. When I looked into the /sys/block/sdb/queue/max_hw_sectors_kb, it shows 1024, which is 2048 sectors. 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. However, this time, still my device received 512 KB (1024) data transfer buffers in scsi_command. Please let me know If I missed any thing here? Thanks and Regards, RD. -- 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
