# Re: [dev] sanei_scsi.c and Linux versions < 2.2.7

From: abel deuring (a.deuring@satzbau-gmbh.de)
Date: Mon Jul 16 2001 - 04:27:40 PDT

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  - In reply to: Douglas Gilbert: "Re: [dev] sanei_scsi.c and Linux versions < 2.2.7"
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  Douglas Gilbert wrote:
  > > Well, the error report could of course be added to sanei_scsi_req_enter,
  > > but a backend should check for this error in sanei_scsi_req_wait too: If
  > > you queue two or more commands and the low level driver does not support
  > > command queueing, sanei_scsi_req_enter puts the second and following
  > > commands into its internal queue, so it cannot return an error from the
  > > SG driver.
  >
  > The reserved buffer is only good for one SCSI command
  > at a time (per file descriptor) and only if it is big
  > enough to hold the size of transfer being requested.
  >
  > Thus when commands are queued there is a risk that
  > subsequent commands will fail with ENOMEM. This "out of
  > memory" situation is more likely to occur with ISA
  > SCSI adapters which can only use the bottom 16 MB of
  > memory for DMA. This is not a hard error and should
  > not be treated as such [IMO]. The reserve buffer
  > more or less guarantees SANE can queue 1 command.
  > If memory is not available to queue 2 or more commands
  > then wait ....

  Doug,

  thanks for helping my memory :) I knew there were even more reasons to
  check ENOMEM late, but I could not remember them while I wrote my mail.

  Abel

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