Add environment SANE_HP_KEEPOPEN...

doc/sane-hp.man

@@ -1,4 +1,4 @@
-.TH sane-hp 5 "09 Oct 2003" "@PACKAGEVERSION@" "SANE Scanner Access Now Easy"
+.TH sane-hp 5 "27 Mar 2004" "@PACKAGEVERSION@" "SANE Scanner Access Now Easy"
 .IX sane-hp
 .SH NAME
 sane-hp \- SANE backend for HP ScanJet scanners
@@ -219,6 +219,19 @@ Only used for OS/2 and along with use of HP PhotoSmart PhotoScanner.
 Must be set to the directory where the directory .sane is located. 
 Is used to save and read the calibration file.
 .TP
+.B SANE_HP_KEEPOPEN_SCSI
+.TP
+.B SANE_HP_KEEPOPEN_USB
+.TP
+.B SANE_HP_KEEPOPEN_DEVICE
+For each type of connection (connect-scsi, connect-usb, connect-device)
+it can be specified if the connection to the device should be kept open ("1")
+or not ("0").
+Usually the connections are closed after an operation is performed.
+Keeping connection open to SCSI-devices can result in errors during device IO
+when the scanner has not been used for some time. By default, USB-connections
+are kept open. Other connections are closed.
+.TP
 .B SANE_HP_RDREDO
 Specifies number of retries for read operation before returning an EOF error.
 Only supported for non-SCSI devices. Default: 1 retry. Time between retries