Re: Alternate ways to do Scatter-Gather from BOT Class driver

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

 



On Tue, 29 Jun 2010, Subs wrote:

> On Tue, Jun 29, 2010 at 12:25 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> > On Mon, 28 Jun 2010, Subs wrote:
> >
> >> Hi All,
> >>
> >> In my class driver I am receiving data transfer buffer as number of
> >> Scatter-Gather lists from SCSI layer to perform data transfers.
> >>
> >> Is there any alternate way to get the transfer buffer from SCSI other
> >> than SG. I wanted to receive the complete data transfer buffer as a
> >> single pointer.
> >
> > As far as I know, there is no alternate way to get the transfer buffer
> > from the SCSI layer.
> >
> > However you can get the effect you want by setting the sg_tablesize
> > field in your scsi_host_template to 1.
> >
> > Just out of curiosity, why are you writing a class driver for the BOT
> > class?  Aren't the two existing drivers in the kernel good enough?
> >
> > Alan Stern
> >
> >
> 
> By changing sg_tablesize to 1, there is no change in number of buffers
> that I am receiving in SG list.

Then you must be doing something wrong.  I just tried changing
sg_tablesize in the usb-storage driver, and as a result the
scatterlists it received contained only one element.  (Of course, in
usb-storage what matters is not the value in the scsi_host_template but
rather the value returned by usb_stor_sg_tablesize.)

> > Just out of curiosity, why are you writing a class driver for the BOT
> > class?  Aren't the two existing drivers in the kernel good enough?
> 
> I am writing my custom class driver, which can do Control and Bulk
> transfers only. This is nowhere related to Mass Storage BOT transfers.

Then why did you mention BOT in the email Subject: line?  Does it refer 
to something other than Bulk-Only-Transport?

Alan Stern

--
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


[Index of Archives]     [Linux Media]     [Linux Input]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [Old Linux USB Devel Archive]

  Powered by Linux