On Wed, Feb 24, 2010 at 10:00 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > 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 Dear Alan, James, Martin, Jens Thanks a lot for your valuable information. I will let all you know, If I see any progress. Thanks and Regards, RD. -- 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
