# Re: Probable Bugs & Suggestions

Rogier Wolff (R.E.Wolff@BitWizard.nl)
Tue, 13 Jan 1998 09:15:50 +0100 (MET)

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David Mosberger-Tang wrote:
>
> >>>>> On Thu, 18 Dec 1997 22:05:34 -0500, Matto Marjanovic <maddog@mir.com> said:
>
> Matto> While a scan is in progress, the microtek backend responds to
> Matto> any requests to change parameters with
> Matto> SANE_STATUS_DEVICE_BUSY... Is this a reasonable behavior?
> Matto> This response is actually not enumerated as a valid response
> Matto> to sane_control_option in the API documentation. Should the
> Matto> frontend retry on its own volition, or pop up an error for
> Matto> the user and drop the issue?
>
> Yeah, this has been a long-standing issue that hasn't been fully resolved
> yet.
>
> I see two reasonable solutions:
>
> 1. Make sane_start() return a special status value when the backend
> does not want to see any control_option() calls while a scan is in
> progress (e.g., something like
> SANE_STATUS_IN_PROGRESS_DO_NOT_TOUCH_OPTION_SETTINGS but maybe not
> quite as verbose... ;-)
>
> 2. Add a option descriptor bit to indicate which options are busy
> during a scan (i.e., which options can't be modified while a scan
> is in progress).
>
> I currently favor the first solution since its simpler and since I'm
> not sure how often there would be backends that have some but not all
> options being busy while a scan is in progress. Other opinions?

What is wrong with the backend returning "busy", and a frontend then
having to conclude "oops, can't seem to do that right now"?

+ No added options
+ Allows for selective "locking".
+ Minimal intrusion in installed base.
- frontends must perform a scan to be able to gray out invalid options.

Roger.

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