On 08/16/2011 02:09 PM, Nicholas A. Bellinger wrote:
<snip>
>> +static enum dma_data_direction tcm_qla2xxx_mapping_dir(struct se_cmd *se_cmd)
>> +{
>> + if (se_cmd->t_tasks_bidi)
>> + return DMA_BIDIRECTIONAL;
>> +
>
> Mmmm, I don't think this is correct. It's my understanding that
> DMA_BIDIRECTIONAL is different from SCSI bidi operation, and that the
> individual bidi payloads should be retaining their individual
> DMA_FROM_DEVICE and DMA_TO_DEVICE usage.. (Boaz CC'ed)
>
Yes! DMA_BIDIRECTIONAL means that the same direct-access buffer could
be written to and read from at the same time. For example a shared
host-DSP buffer could be that case. It tells the (true) IOMMU to
let both type of access on this single buffer.
In SCSI bidi commands we have two *separate* buffers. One buffer is
only read to. Second buffer is only written from (Yes Initiator view).
But each buffer is always only DMA_FROM_DEVICE or DMA_TO_DEVICE.
You should I identify the two different buffers and only flip for
each one individually so something like
+ if (se_cmd->t_tasks_bidi)
+ // TODO: Call a routine to also flip the se_cmd->t_tasks_bidi direction
>
>> + switch (se_cmd->data_direction) {
>> + case DMA_TO_DEVICE:
>> + return DMA_FROM_DEVICE;
>> + case DMA_FROM_DEVICE:
>> + return DMA_TO_DEVICE;
>> + case DMA_NONE:
>> + default:
>> + return DMA_NONE;
>> + }
>> +}
>> +
Cheers
Boaz
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