Il 25/07/2012 17:28, Boaz Harrosh ha scritto: >> 1) what I get is a scsi_cmnd which contains an N-element scatterlist. >> >> 2) virtio-scsi has to build the "packet" that is passed to the hardware >> (it does not matter that the hardware is virtual). This packet (per >> virtio-scsi spec) has an N+1-element scatterlist, where the first >> element is a request descriptor (struct virtio_scsi_cmd_req), and the >> others describe the written data. > > Then "virtio-scsi spec" is crap. It overloads the meaning of > "struct scatterlist" of the first element in an array. to be a > "struct virtio_scsi_cmd_req". What the holy fuck? The first element simply _points_ to the "struct virtio_scsi_cmd_req", just like subsequent elements point to the data. And the protocol of the device is _not_ a struct scatterlist[]. The virtio _API_ takes that array and converts to a series of physical address + offset pairs. > Since you need to change the standard to support chaining then > it is a good time to fix this. Perhaps it is a good time for you to read the virtio spec. You are making a huge confusion between the LLD->virtio interface and the virtio->hardware interface. I'm talking only of the former. >> 3) virtio takes care of converting the "packet" from a scatterlist >> (which currently must be a flat one) to the hardware representation. >> Here a walk is inevitable, so we don't care about this walk. > > "hardware representation" you mean aio or biovec, what ever the > IO submission path uses at the host end? No, I mean the way the virtio spec encodes the physical address + offset pairs. I stopped reading here. Paolo -- 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
