Re: Maximum data size in a single transfer for MS driver

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [SCSI Target Devel]     [Linux SCSI Target Infrastructure]     [Kernel Newbies]     [IDE]     [Security]     [Git]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux ATA RAID]     [Linux IIO]     [Samba]     [Device Mapper]
  Powered by Linux