On 08/18/2009 09:22 AM, Madhavi Manchala wrote: > Dear All, > > I have seen that SCSI supports bi-directional commands > DMA_BIDIRECTIONAL. However, I did not get such type of commands in my > mass storage driver. My device supports bi-directional data transfers. > My question is, how can I get such type of requests to my mass storage > driver? If so, how can I handle the IN and OUT buffers? Are there > separate buffers for both? Is there any support for the bi-directional > in the current SCSI implementation? I am currently using the 2.6.28 > kernel code. > > We have only one pointer for data buffer instead of two, one for data > OUT and one for data IN in command block. There is only one length > variable. How can we use the OUT and IN buffers? How can I pass > different IN length and OUT length to lower stack from SCSI layer? > > Is there any thing need to be changed in the SCSI layer code to handle > the bi-directional data transfers? > > Please point to me some links which shows the bi-directional data transfers. > > Thanks in advance. > > With Regards, > Madhavi M. > -- > 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 Bidi is fully supported since 2.6.25 If you want example of how to issue bidi commands you can see these two files: block/bsg.c drivers/scsi/osd/osd_initiator.c Basically you allocate two struct request one for OUT one for IN. You map some memory on them and do "out_req->next_rq = in_req;" And you execute the out_req. These two request will go together as one bidi request. On the scsi-driver side you do: if (scsi_bidi_cmnd(cmnd)) { in_sgl = scsi_in(cmnd)->table.sgl; in_nents = scsi_in(cmnd)->table.nents; in_bytes = scsi_in(cmnd)->length; /* Same thing for out */ out_sgl = scsi_out(cmnd)->table.sgl; ... } scsi_in() and scsi_out() will return a pointer or NULL if the cmnd does not have a buffer in this direction. So for example scsi_in() is always used on receive regardless if it is a bidi or a uni_read. NOTE: in bidi_commands scsi_bidi_cmnd(cmnd) == true; but cmnd->sc_data_direction == DMA_TO_DEVICE; DMA_BIDIRECTIONAL is *never* returned from scsi and it means something else inside the DMA engines. For example driver that supports bidi see: drivers/scsi/iscsi_tcp.c drivers/scsi/scsi_debug.c (Search for "scsi_in" and "scsi_out") What type of scsi-device are you using? what bidi commands? Have a good day Boaz -- 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
