343 lines
9.3 KiB
Groff
343 lines
9.3 KiB
Groff
.\" gsc.4 - manual page for the scanner device driver `gsc'
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.\"
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.\"
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.\" Copyright (c) 1995 Gunther Schadow. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by Gunther Schadow.
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.\" 4. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd January 9, 1995
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.Os
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.Dt GSC 4 i386
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.Sh NAME
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.Nm gsc
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.Nd a device driver for a handy scanner
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.Sh SYNOPSIS
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.In machine/gsc.h
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.Pp
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.Cd Minor number bits: Ar uu d g p ...
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.Bl -tag -width "uu " -compact -offset indent
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.It Ar uu
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unit gsc0 .. gsc3
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.It Ar d
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selects logging of
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.Em debug
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messages
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.It Ar g
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selects
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.Em bitmap
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vs.
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.Em graymap
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output
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.It Ar p
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selects
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.Em raw
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vs. portable
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.Em pnm
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output
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.El
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.Sh DESCRIPTION
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The
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.Nm
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character device driver currently handles only the
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Genius GS-4500 handy scanner.
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It operates in pure DMA modes, although
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the hardware could be set up to work with irq.
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I had neither enough
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documentation nor experience in writing interrupt driven device
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drivers.
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.Pp
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The device can operate at four different
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.Em resolutions :
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100, 200,
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300 and 400dpi.
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It produces a simple bitmap with the most significant
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bit at the left side.
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The driver can optionally output the famous and
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likely simple portable bitmap file format
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.Xr pbm 5
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by Jef Poskanzer.
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Thus the scans can easily processed by any graphic package around
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(
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.Xr xpaint 1 ,
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.Xr xv 1 ,
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.Xr xli 1
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only to name some of them ...). In
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.Em raw
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mode a
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bit which is set means a black pixel because the scanner detects black
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points on white paper.
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On the other hand, because pnm format describes
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intensities of electron beams in video screens a set bit in
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.Em pbm
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mode means a white pixel.
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.Pp
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The
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.Em width
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of the output bitmap is fixed as given by the
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resolution value.
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However, the
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.Em height
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of the bitmap must be
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supplied in
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.Em pnm
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mode since the driver must know at what time the
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.Sq end-of-file
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shall be reached.
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With this feature you are able to
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directly copy the scanner output into a pbm file with
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.Xr cat 1 .
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Of course you can obtain a similar effect by using
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.Xr dd 1
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with the driver in
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.Em raw
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mode.
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.Pp
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The
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.Em graymap
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output mode is not yet implemented into the driver.
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It is even questionable if external programs would not do this job
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better thereby not counting to the size of the kernel.
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Even though, I
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do not know of tools which produce a graymap from a halftone bitmap.
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.Pp
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The ioctl requests that are served by
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.Nm
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are listed below.
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There is a utility, called
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.Xr sgsc 1 ,
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that provides access to these
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requests from within shell.
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.Bl -tag -width Ds
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.It GSC_SRES int
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Set the
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.Em resolution
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value.
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If this call is made after the first
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read access to the device there will be no effect unless the device is
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closed and opened again.
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.It GSC_GRES int
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Get current resolution in dots per inch (dpi).
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.It GSC_SRESSSW void
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Set resolution value from selector switch.
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The driver must be in an
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open though untouched state otherwise the request will fail and
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.Xr errno 2
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is set to
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.Er EBUSY .
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.It GSC_SWIDTH int
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Set the
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.Em width
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of the bitmap.
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Actually, this is an alternative
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way of setting the resolution, since any allowed resolution matches
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exactly one width.
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Allowed are listed in the table below.
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.Bl -tag -width resolution -compact -offset indent
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.It resolution
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width
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.It 100 dpi
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424 pixels
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.It 200 dpi
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840 pixels
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.It 300 dpi
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1264 pixels
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.It 400 dpi
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1648 pixels
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.It ?
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1696 pixels
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.It ?
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2544 pixels
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.It ?
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3648 pixels
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.El
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.Pp
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Values which are not reported in the above table will cause the ioctl
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call to fail with
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.Xr errno 2
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set to
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.Er EINVAL .
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.Pp
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As you can see, there are width values > 1696.
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This does, however, not
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mean that you can obtain scanned lines longer than the width of your
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scanner or by higher resolutions.
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Actually, the resolution is selected
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by only by the hardware switch.
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Any line that is longer than what is
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defined for the actual resolution will be undefined (usually white) on
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the right part that is exceeding the standard line.
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.It GSC_GWIDTH int
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Get current width of the bitmap in pixels.
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.It GSC_SHEIGHT int
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Set the
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.Em height
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of the bitmap in
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.Em pnm
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mode.
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This is actually
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a limit on the amount of lines scannable after the first read
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operation.
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When the limit is reached read will return 0. However, the
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device is turned off only when a close is performed (either
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explicitly or implicitly on exit of the calling process).
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.It GSC_GHEIGHT int
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Get the current height of the bitmap.
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.It GSC_SBLEN int
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Set the length of the buffer used internally to do the DMA transfer.
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The buffer length is supplied in lines of the bitmap.
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Since the buffer
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size limit is (currently) 0x3000 bytes the maximum number of lines
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allowed will vary with the width of each line.
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This upper limit is
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checked before it overwrites the current value and passes an
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.Er ENOMEM
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in the
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.Xr errno 2
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variable.
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However, since the bitmap width can change
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after a buffer length was selected a read request may fail with
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.Er ENOMEM
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if the buffer length turns out too high.
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It is generally wise to
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choose long buffers rather than go save in order to obtain better
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output.
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.It GSC_GBLEN int
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Get the current buffer length in lines.
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.It GSC_SBTIME int
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Set the timeout for the completion of reading one buffer.
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Since a
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handy scanner is a human/computer interface timeout values are usually
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higher than those of a flat scanner.
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Default is 15 seconds.
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After
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timeout is reached the read operation will fail with
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.Er EBUSY .
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Note that
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the timeout timer starts anew for each buffer to be read and thus does
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not cause you to scan faster for longer images.
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BLEN/BTIME is similar
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as MIN/TIME in
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.Xr termios 4 .
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.It GSC_GBTIME int
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Get the current buffer timeout.
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.El
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.Pp
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All ioctl requests that modify a parameter except GSC_SBTIME do not
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have an effect on an ongoing scan process, i.e. after the first read
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request that follows open.
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You must close the device and open it again
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for the new selections to take effect.
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Consequently, the selections
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are not reset when you close or open the device.
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.Pp
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Similarly, requests that read a value do not report the value that is
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used for the ongoing scan process.
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The values needed during the scan
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process are saved when it starts and thus are not accessed by ioctl
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requests.
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.Pp
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The BTIME value does, however, have an immediate effect on the ongoing
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scan.
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Thus the timeout can for example be set to long until the user
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starts scanning. It can then be set to a short amount to react
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(nearly) immediately when the user stops.
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Note that the user should be
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left time to at least fill one buffer without having to haste.
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.Pp
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Note that the
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.Em pbm
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versus
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.Em raw
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mode selection is done by the
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minor number not by ioctl requests.
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In
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.Em raw
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mode the selected
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height of the bitmap will have no effect.
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.Sh FILES
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.Bl -tag -width /dev/gsc0pd
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.It Pa /dev/gsc0
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device node for
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.Em raw
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output, has minor number 0.
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.It Pa /dev/gsc0d
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device node for
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.Em raw
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output emitting
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.Em debug
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messages if the
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GSCDEBUG option was given at compile time, has minor number 32.
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.It Pa /dev/gsc0p
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device node for output in
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.Em pbm
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file format, has minor number 8.
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.It Pa /dev/gsc0pd
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device node for
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.Em pbm
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and
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.Em debug
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mode, has minor number 40.
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.El
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.Sh EXAMPLES
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.Bd -literal -offset indent
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dd if=/dev/gsc0 of=rawfile bs=(width/8) count=(height)
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cat /dev/gsc0p > pbmfile
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.Ed
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.Sh DIAGNOSTICS
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.Bl -tag -width Cd
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.It GSCDEBUG
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When you define this name as an `option' in the kernel configuration
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you can get debug output if you access the driver with a minor number
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whose debug bit (i.e. bit 5 out of 7) is set.
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.El
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.Sh SEE ALSO
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.Xr cat 1 ,
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.Xr dd 1 ,
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.Xr pbmtopgm 1 ,
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.Xr pnm 1 ,
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.Xr sgsc 1 ,
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.Xr close 2 ,
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.Xr intro 2 ,
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.Xr ioctl 2 ,
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.Xr open 2 ,
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.Xr read 2 ,
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.Xr termios 4 ,
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.Xr pbm 5
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.Sh AUTHORS
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.An Gunther Schadow Aq gusw@fub46.zedat.fu-berlin.de
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.Sh BUGS
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Even though the scanner device has a little switch by which you should
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be able to select one of the four resolution modes, I could not yet
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determine how to read its status.
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Unless this is not fixed the driver
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depends on the value passed by means of
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.Xr ioctl 2
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which need not match
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what is selected by the hardware.
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