*nix Documentation Project
·  Home
 +   man pages
·  Linux HOWTOs
·  FreeBSD Tips
·  *niX Forums

  man pages->FreeBSD man pages -> i386/gsc (4)              



NAME    [Toc]    [Back]

     gsc -- a device driver for a handy scanner

SYNOPSIS    [Toc]    [Back]

     #include <machine/gsc.h>

     Minor number bits: uu d g p ...
	   uu	unit gsc0 .. gsc3
	   d	selects logging of debug messages
	   g	selects bitmap vs.  graymap output
	   p	selects raw vs. portable pnm output

DESCRIPTION    [Toc]    [Back]

     The gsc character device driver currently handles only the Genius GS-4500
     handy scanner.  It operates in pure DMA modes, although the hardware
     could be set up to work with irq.	I had neither enough documentation nor
     experience in writing interrupt driven device drivers.

     The device can operate at four different resolutions: 100, 200, 300 and
     400dpi.  It produces a simple bitmap with the most significant bit at the
     left side.  The driver can optionally output the famous and likely simple
     portable bitmap file format pbm(5) by Jef Poskanzer.  Thus the scans can
     easily processed by any graphic package around ( xpaint(1), xv(1), xli(1)
     only to name some of them ...).  In raw mode a bit which is set means a
     black pixel because the scanner detects black points on white paper.  On
     the other hand, because pnm format describes intensities of electron
     beams in video screens a set bit in pbm mode means a white pixel.

     The width of the output bitmap is fixed as given by the resolution value.
     However, the height of the bitmap must be supplied in pnm mode since the
     driver must know at what time the `end-of-file' shall be reached.	With
     this feature you are able to directly copy the scanner output into a pbm
     file with cat(1).	Of course you can obtain a similar effect by using
     dd(1) with the driver in raw mode.

     The graymap output mode is not yet implemented into the driver.  It is
     even questionable if external programs would not do this job better
     thereby not counting to the size of the kernel.  Even though, I do not
     know of tools which produce a graymap from a halftone bitmap.

     The ioctl requests that are served by gsc are listed below.  There is a
     utility, called sgsc(1), that provides access to these requests from
     within shell.

     GSC_SRES int
	     Set the resolution value.	If this call is made after the first
	     read access to the device there will be no effect unless the
	     device is closed and opened again.

     GSC_GRES int
	     Get current resolution in dots per inch (dpi).

     GSC_SRESSSW void
	     Set resolution value from selector switch.  The driver must be in
	     an open though untouched state otherwise the request will fail
	     and errno(2) is set to EBUSY.

     GSC_SWIDTH int
	     Set the width of the bitmap.  Actually, this is an alternative
	     way of setting the resolution, since any allowed resolution
	     matches exactly one width.  Allowed are listed in the table
		   resolution  width
		   100 dpi     424 pixels
		   200 dpi     840 pixels
		   300 dpi     1264 pixels
		   400 dpi     1648 pixels
		   ?	       1696 pixels
		   ?	       2544 pixels
		   ?	       3648 pixels

	     Values which are not reported in the above table will cause the
	     ioctl call to fail with errno(2) set to EINVAL.

	     As you can see, there are width values > 1696.  This does, however,
 not mean that you can obtain scanned lines longer than the
	     width of your scanner or by higher resolutions.  Actually, the
	     resolution is selected by only by the hardware switch.  Any line
	     that is longer than what is defined for the actual resolution
	     will be undefined (usually white) on the right part that is
	     exceeding the standard line.

     GSC_GWIDTH int
	     Get current width of the bitmap in pixels.

     GSC_SHEIGHT int
	     Set the height of the bitmap in pnm mode.	This is actually a
	     limit on the amount of lines scannable after the first read operation.
  When the limit is reached read will return 0. However,
	     the device is turned off only when a close is performed (either
	     explicitly or implicitly on exit of the calling process).

     GSC_GHEIGHT int
	     Get the current height of the bitmap.

     GSC_SBLEN int
	     Set the length of the buffer used internally to do the DMA transfer.
  The buffer length is supplied in lines of the bitmap.
	     Since the buffer size limit is (currently) 0x3000 bytes the maximum
 number of lines allowed will vary with the width of each
	     line.  This upper limit is checked before it overwrites the current
 value and passes an ENOMEM in the errno(2) variable.	However,
 since the bitmap width can change after a buffer length was
	     selected a read request may fail with ENOMEM if the buffer length
	     turns out too high.  It is generally wise to choose long buffers
	     rather than go save in order to obtain better output.

     GSC_GBLEN int
	     Get the current buffer length in lines.

     GSC_SBTIME int
	     Set the timeout for the completion of reading one buffer.	Since
	     a handy scanner is a human/computer interface timeout values are
	     usually higher than those of a flat scanner.  Default is 15 seconds.
  After timeout is reached the read operation will fail with
	     EBUSY.  Note that the timeout timer starts anew for each buffer
	     to be read and thus does not cause you to scan faster for longer
	     images.  BLEN/BTIME is similar as MIN/TIME in termios(4).

     GSC_GBTIME int
	     Get the current buffer timeout.

     All ioctl requests that modify a parameter except GSC_SBTIME do not have
     an effect on an ongoing scan process, i.e. after the first read request
     that follows open.  You must close the device and open it again for the
     new selections to take effect.  Consequently, the selections are not
     reset when you close or open the device.

     Similarly, requests that read a value do not report the value that is
     used for the ongoing scan process.  The values needed during the scan
     process are saved when it starts and thus are not accessed by ioctl

     The BTIME value does, however, have an immediate effect on the ongoing
     scan.  Thus the timeout can for example be set to long until the user
     starts scanning.  It can then be set to a short amount to react (nearly)
     immediately when the user stops.  Note that the user should be left time
     to at least fill one buffer without having to haste.

     Note that the pbm versus raw mode selection is done by the minor number
     not by ioctl requests.  In raw mode the selected height of the bitmap
     will have no effect.

FILES    [Toc]    [Back]

     /dev/gsc0	  device node for raw output, has minor number 0.

     /dev/gsc0d   device node for raw output emitting debug messages if the
		  GSCDEBUG option was given at compile time, has minor number

     /dev/gsc0p   device node for output in pbm file format, has minor number

     /dev/gsc0pd  device node for pbm and debug mode, has minor number 40.

EXAMPLES    [Toc]    [Back]

	   dd if=/dev/gsc0 of=rawfile bs=(width/8) count=(height)

	   cat /dev/gsc0p > pbmfile

DIAGNOSTICS    [Toc]    [Back]

     GSCDEBUG	   When you define this name as an `option' in the kernel configuration
 you can get debug output if you access the
		   driver with a minor number whose debug bit (i.e. bit 5 out
		   of 7) is set.

SEE ALSO    [Toc]    [Back]

     cat(1), dd(1), pbmtopgm(1), pnm(1), sgsc(1), close(2), intro(2),
     ioctl(2), open(2), read(2), termios(4), pbm(5)

AUTHORS    [Toc]    [Back]

     Gunther Schadow <gusw@fub46.zedat.fu-berlin.de>

BUGS    [Toc]    [Back]

     Even though the scanner device has a little switch by which you should be
     able to select one of the four resolution modes, I could not yet determine
 how to read its status.  Unless this is not fixed the driver depends
     on the value passed by means of ioctl(2) which need not match what is
     selected by the hardware.

FreeBSD 5.2.1			January 9, 1995 		 FreeBSD 5.2.1
[ Back ]
 Similar pages
Name OS Title
asc FreeBSD device driver for a GI1904-based hand scanner
sgsc FreeBSD set the options of the gsc scanner device
ss OpenBSD SCSI Scanner device
sasc FreeBSD set the options of the asc scanner device
el FreeBSD Ethernet driver for 3Com Etherlink 3C501 device driver
bfs IRIX big file scanner
hil HP-UX HP-HIL device driver
ed FreeBSD ethernet device driver
fdes_to_drivername IRIX determine the driver name for the device
iic FreeBSD I2C generic i/o device driver
Copyright © 2004-2005 DeniX Solutions SRL
newsletter delivery service