On 22/03/2022 14:03, Hannes Reinecke wrote:
As mentioned in the cover letter response, it just seems best to keep
the normal scsi_cmnd payload but have other means to add on the
internal command data, like using host_scribble or scsi_cmnd priv data.
Well; I found that most drivers I had been looking at the scsi command
payload isn't used at all; the drivers primarily cared about the
(driver-provided) payload, and were completely ignoring the scsi command
payload.
Similar for ATA/libsas: you basically never issue real scsi commands,
but either 'raw' ATA requests or SCSI TMFs. None of which are scsi
commands, so providing them is a bit of a waste.
(And causes irritations, too, as a scsi command requires associated
pointers like ->device etc to be set up. Which makes it tricky to use
for the initial device setup.)
A problem I see is that in scsi_mq_init_request() we allocate memories
like sense_buffer and prot_sdb and store the pointers in the scsi_cmnd
payload. If we then reuse a scsi_cmnd payload as an "internal" command
payload then this data may be lost.
It might be possible to reuse the scsi cmnd payload for the "internal",
but I would rather not get hung up on it now if possible.
Thanks,
John
