On 4/11/10, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: Dear Alan, > > >> Yes, Ramya's transfer was one URB with a scatter-gather list of ~120 > > >> entries. He was working on a UASP driver that sets the max_sectors > > >> field in scsi_host_template to 960 or 1024, which makes some of the > > >> sglists very large. > > > > > > Then his driver is buggy. It should limit the length of scatter-gather > > > lists allowed by the host according to what the HCD can support, the > > > way usb-storage does: > > > > > > host->sg_tablesize = usb_stor_sg_tablesize(intf); > > > > Dear Alan, > > > > My device is a UASP device, however I am testing the default usb > > storage driver for maximum transfer buffer sizes as my device supports > > upto 1 MB transfer buffer sizes. There is a thread about the "Maximum > > data size in a single transfer for MS driver", which we have discussed > > in the month February, 2010. The link for the thread is as follows. > > http://marc.info/?t=126641036700002&r=3&w=2 > > > > NOTE: As we discussed in the above thread, the function, named > > store_max_sectors, has changed in 2.6.34-rc2 kernel version. > > That should not have made any difference. We are talking about > sg_tablesize, not max_sectors. In xhci-pci.c, sg_tablesize is set to > TRBS_PER_SEGMENT - 1, or 63. Therefore it should not be possible for > you to receive a transfer request containing more than 63 scatterlist > elements. But Sarah said (see above) that you submitted a request with > ~120 elements. This means something is wrong somewhere. I can accept you that sg_tablesize and max_sectors are different. Here is what Sarah said in her previous email. > > >> Yes, Ramya's transfer was one URB with a scatter-gather list of ~120 > > >> entries. He was working on a UASP driver that sets the max_sectors > > >> field in scsi_host_template to 960 or 1024, which makes some of the > > >> sglists very large According to her, she saw ~120 entries when I change the max_sectors value to 960 or 1024 in the scsi_host_template. I want to say one thing here that I am testing the default usb storage driver for 960 or 1024 sectors with my UASP device.When I am testing the default usb storage driver with 960 max_sectors Sarah saw ~120 scatter-gather list entries. Please let me know If I am wrong. I am not able to test my UASP device with default storage driver when max_sectors value is changed to 960 or 1024 in the scsi_host_template. However, when max_sectors value is 240 or 720 I am able to do all the operations with my UASP device using the default mass storage driver. Please let me know if you need any additional information. Thanks and Regards, Ramya. -- 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
