Messages in this thread | | | Date | Fri, 3 Aug 2018 12:56:23 +1000 (AEST) | From | Finn Thain <> | Subject | Re: [PATCH] scsi:NCR5380: remove same check condition in NCR5380_select |
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On Thu, 2 Aug 2018, Michael Schmitz wrote:
> > This redundant load of the ICR has been in the driver code for a long > time. There's a small chance it is intentional,
Actually, it is intentional.
> so at least minimal testing might be in order. >
Minimal testing is almost useless if you are trying to prove the absence of race conditions. SCSI arbitration is a race between targets by design; so a race between the CPU and the 5380 is going to be hard to observe.
> Finn - does the ICR_ARBITRATION_LOST bit have to be cleared by a write > to the mode register? >
Something like that: the write to the mode register does clear the ICR_ARBITRATION_LOST bit, because it clears the MR_ARBITRATE bit.
> In that case, the first load would have been redundant and can be > omitted without changing driver behaviour?
This code is a faithful rendition of the arbitration flow chart in the datasheet, so even if you are right, I wouldn't want to change the code.
Besides, I think your argument assumes that ICR and MR are synchronized, and also assumes that targets are obeying the spec.
--
> Cheers, > > Michael > >
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