'\" te
.\" Copyright (c) 2007, Sun Microsystems, Inc.  All Rights Reserved
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing.  See the License for the specific language governing permissions and limitations under the License.
.\" When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE.  If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
.TH ugen 7D "3 Dec 2008" "SunOS 5.11" "Devices"
.SH NAME
ugen \- USB generic driver
.SH SYNOPSIS
.LP
.nf
\fBNode Name@unit-address\fR
.fi

.LP
.nf
\fB#include <sys/usb/clients/ugen/usb_ugen.h>\fR
.fi

.SH DESCRIPTION
.sp
.LP
\fBugen\fR is a generic USBA (Solaris USB Architecture) compliant client
character driver that presents USB devices to applications through a standard
\fBopen\fR(2), \fBclose\fR(2), \fBread\fR(2), \fBwrite\fR(2),
\fBaioread\fR(3C), \fBaiowrite\fR(3C) Unix interface. Uninterpreted raw data
are transfered to and from the device via file descriptors created for each USB
endpoint. Status is obtained by reading file descriptors created for endpoint
and full device status.
.sp
.LP
\fBugen\fR supports control, bulk, isochronous and interrupt (in and  out)
transfers. \fBlibusb\fR(3LIB) uses \fBugen\fR to access devices that do not
contain drivers (such as digital cameras and PDAs). Refer to
\fB/usr/sfw/share/doc/libusb/libusb.txt\fR for details.
.SH BINDING
.sp
.LP
In general, no explicit binding of the \fBugen\fR driver is necessary because
\fBusb_mid\fR(7D) is the default driver for devices without a class or vendor
unique driver. \fBusb_mid\fR(7D) creates the same logical device names as
\fBugen\fR, but only if no child interfaces are explicitly bound to \fBugen\fR.
If it is necessary to bind \fBugen\fR explicitly to a device or interface, the
following section explains the necessary steps.
.sp
.LP
\fBugen\fR can bind to a device with one or more interfaces in its entirety, or
to a single interface of that device. The binding type depends on information
that is passed to \fBadd_drv\fR(1M) or \fBupdate_drv\fR(1M).
.sp
.LP
An \fBadd_drv\fR(1M) command binds \fBugen\fR to a list of device types it is
to control. \fBupdate_drv\fR(1M) adds an additional device type to the list of
device types being managed by the driver.
.sp
.LP
Names used to bind drivers can be found in \fB/var/adm/messages\fR. When a
device is on-lined after hot insertion, and no driver is found, there will be
an entry containing:
.sp
.in +2
.nf
USB 2.0 device (usb<vid>,<pid>)...
.fi
.in -2

.sp
.LP
where vid is the USB vendor identifier in hex and pid is the  product
identifier in hex supplied by the device  descriptor \fBusb_dev_descr\fR(9S).
.sp
.LP
When using ugen for the first time, you must add the  driver utilizing
\fBadd_drv\fR(1M), using a command of the following form:
.sp
.in +2
.nf
Assuming that the vid is 472 and pid is b0b0:

add_drv -n -m '* <device perms> <owner> <group>' 
   -i '"usb472,b0b0"' ugen
.fi
.in -2

.sp
.LP
If the command fails with:
.sp
.in +2
.nf
(ugen) already in use as a driver or alias.
.fi
.in -2

.sp
.LP
\&...add the device using \fBupdate_drv\fR(1M):
.sp
.in +2
.nf
update_drv -a -m '* <device perms> <owner> <group>'
   -i '"usb472,b0b0"' ugen 
.fi
.in -2

.sp
.LP
This binds \fBugen\fR to the entire device.
.sp
.LP
If ugen only binds to one interface of the device, use the following
driver_alias instead of usb<vid>,<pid>:
.sp
.in +2
.nf
       usbif<vid>,<pid>.config<cfg value>.<interface number>
.fi
.in -2

.sp
.LP
where cfg value is the value of bConfigurationValue in the configuration
descriptor (\fBusb_cfg_descr\fR(9S)). For example "usbif1234,4567.config1.0."
.sp
.LP
Note that you can use update_drv to  also  remove  bindings. Please see
\fBupdate_drv\fR(1M) for more information.
.sp
.LP
After a successful add_drv or update_drv, remove the device and reinsert. Check
with the \fBprtconf\fR(1M) -D option to determine if \fBugen\fR is successfully
bound to the device and the nodes created in /dev/usb/<vid>.<pid> (see below).
.sp
.LP
An example showing how to bind a child device representing interface 0 of
configuration 1 of a composite device follows:
.sp
.in +2
.nf
update_drv -a -m '* 0666 root sys'
    -i '"usbif472,b0b0.config1.0"' ugen
.fi
.in -2

.sp
.LP
Note that you can completely uninstall the \fBugen\fR driver and delete it from
the system by doing:
.sp
.in +2
.nf
pkgrm SUNWugen
.fi
.in -2

.sp
.LP
Any \fBpkgadd\fR of SUNWugen after the \fBpkgrm\fR reactivates any pre-existing
ugen driver device-bindings.
.sp
.LP
Any pre-existing ugen driver device-bindings are preserved across operating
system upgrades.
.SH LOGICAL DEVICE NAME FORMAT
.sp
.LP
For each device or child device it manages, \fBugen\fR creates one logical
device name for device-wide status and one logical device name for endpoint 0.
\fBugen\fR also creates logical device names for all other endpoints within the
device node's binding scope (interface or device), plus logical device names
for their status.
.sp
.LP
If separate \fBugen\fR instances control different interfaces of the same
device, the device-wide status and endpoint logical device names created for
each instance will share access to the same source or endpoint pipes. For
example, a device with two interfaces, each operated by their own \fBugen\fR
instance, will show \fBendpoint0\fR as \fBif0cntrl0\fR to the first interface,
and will show it as \fBif1cntrl0\fR to the second interface. Both of these
logical device names share \fBendpoint0\fR. Likewise for the same device,
\fBugen\fR makes the device-wide status available as \fBif0devstat\fR to the
first interface and as \fBif1devstat\fR to the second interface.
\fBif0devstat\fR and \fBif1devstat\fR both return the same data.
.sp
.LP
Any \fBugen\fR logical device name can be held open by only one user at a time,
regardless of whether the\fB O_EXCL\fR flag passed to \fBopen\fR(2). When a
single pipe or data source is shared by multiple logical device names, such as
if[0,1]cntrl0 or if[0,1]devstat above, more than one logical device name
sharing the pipe or data source can be open at a time.  However, only one user
may access the shared pipe or data source at a time, regardless of the logical
device name used for access.
.sp
.LP
When \fBugen\fR is bound to an entire device, the following logical device
names are created (each on a single line). \fIN\fR represents the instance
number of the device type.
.sp
.in +2
.nf
Endpoint 0 (default endpoint):

        /dev/usb/<vid>.<pid>/<N>/cntrl0
        /dev/usb/<vid>.<pid>/<N>/cntrl0stat

    For example:

        /dev/usb/472.b0b0/0/cntrl0
        /dev/usb/472.b0b0/0/cntrl0stat

Configuration index 1, Endpoints > 0, alternate 0:

        /dev/usb/<vid>.<pid>/<N>/if<interface#>
                                <in|out|cntrl><endpoint#>
        /dev/usb/<vid>.<pid>/<N>/if<interface#>
                                <in|out|cntrl><endpoint#>stat

    For example:

        /dev/usb/472.b0b0/0/if0in1
        /dev/usb/472.b0b0/0/if0in1stat

Configuration index 1, Endpoints > 0, alternate > 0:

        /dev/usb/<vid>.<pid>/<N>/if<interface#>.
                                <alternate><in|out|cntrl><endpoint#>
        /dev/usb/<vid>.<pid>/<N>/if<interface#>.
                                <alternate<in|out|cntrl><endpoint#>stat

    For example:
 
        /dev/usb/472.b0b0/0/if0.1in3
        /dev/usb/472.b0b0/0/if0.1in3stat

Configuration index> 1, Endpoints > 0, alternate 0:
        /dev/usb/<vid>.<pid>/<N>/cfg<value>if<interface#>
                                <in|out|cntrl><endpoint#>
        /dev/usb/<vid>.<pid>/<N>/cfg<value>if<interface#>
                                <in|out|cntrl><endpoint#>stat

    For example:

       /dev/usb/472.b0b0/0/cfg2if0in1
       /dev/usb/472.b0b0/0/cfg2if0in1stat
    
    Note that the configuration value from the configuration
    descriptor indexed by the configuration index is used in
    the node name and not the configuration index itself.

Configuration index> 1, Endpoints > 0, alternate > 0:
        /dev/usb/<vid>.<pid>/<N>/cfg<value>if<interface#>.
                                <alternate<in|out|cntrl><endpoint#>
        /dev/usb/<vid>.<pid>/<N>/cfg<value>if<interface#>.
                                <alternate<in|out|cntrl><endpoint#>stat

    For example:

        /dev/usb/472.b0b0/0/cfg2if0.1in1
        /dev/usb/472.b0b0/0/cfg2if0.1in1stat

  Device status:

        /dev/usb/<vid>.<pid>/<N>/devstat

    For example:

        /dev/usb/472.b0b0/0/devstat
.fi
.in -2

.sp
.LP
When \fBugen\fR is bound to a single device interface, the following logical
device nodes are created:
.sp
.in +2
.nf
Endpoint 0 (default endpoint):

         /dev/usb/<vid>.<pid>/<N>/if<interface#>cntrl0
         /dev/usb/<vid>.<pid>/<N>/if<interface#>cntrl0stat

    For example:

         /dev/usb/472.b0b0/0/if0cntrl0
         /dev/usb/472.b0b0/0/if0cntrl0stat

Device status:
        /dev/usb/<vid>.<pid>/<N>/if<interface#>devstat

    For example:
        /dev/usb/472.b0b0/0/if0devstat
.fi
.in -2

.sp
.LP
The format for all other logical device names is identical to the format used
when \fBugen\fR is bound to the entire device.
.sp
.LP
Opening the endpoint of a different configuration or different alternate
interface will cause an implicit change of configuration or a switch to an
alternate interface. A configuration change is prohibited when any non-zero
endpoint device nodes are open. An alternate interface switch is prohibited if
any endpoint in the same interface is open.
.SH HOT-PLUGGING
.sp
.LP
A device may be hot-removed at any time. Following hot-removal, the device
status changes to USB_DEV_STAT_DISCONNECTED, the status of open endpoints
change to USB_LC_STAT_DISCONNECTED upon their access, and all subsequent
transfer requests fail. Endpoints are reactivated by first reinserting the
device and then closing and reopening all endpoints that were open when the
device was disconnected.
.SH CPR (CHECKPOINT/RESUME)
.sp
.LP
CPR (Checkpoint/Resume) may be initiated at any time and is treated similarly
to a hot-removal. Upon successful suspend and resume, all subsequent transfer
requests fail as an indication to the application to reinitialize. Applications
should close and reopen all endpoints to reinstate them. All endpoint and
device status on Resume (before close and reopen) is USB_LC_STAT_SUSPENDED. A
system suspend will fail while \fBugen\fR is performing a transfer.
.SH DEVICE POWER MANAGEMENT
.sp
.LP
Devices which support remote wakeup can be power managed when they have no open
logical device nodes. When an application opens the first logical device node
of a device, that application should assume that a reinitialization of device
state is required.
.SH DEVICE STATUS MANAGEMENT
.sp
.LP
Applications can monitor device status changes by reading the device status
from the device status logical name. When opened without O_NONBLOCK and
O_NDELAY, all reads from that file descriptor (with the exception of the the
intial read that follows the open) block until a device status change occurs.
Calls to read will always return immediately if opened with \fBO_NONBLOCK\fR or
\fBO_NDELAY\fR. Nonblocking calls to read which have no data to return, return
no error and zero bytes read.
.sp
.LP
Device statuses are:
.sp
.ne 2
.mk
.na
\fBUSB_DEV_STAT_ONLINE\fR
.ad
.RS 29n
.rt  
Device is available.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_DEV_STAT_DISCONNECTED\fR
.ad
.RS 29n
.rt  
Device has been disconnected.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_DEV_STAT_RESUMED\fR
.ad
.RS 29n
.rt  
Device has been resumed, however, endpoints which were open on suspend have not
yet been closed and reopened.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_DEV_STAT_UNAVAILABLE\fR
.ad
.RS 29n
.rt  
Device has been reconnected, however, endpoints which were open on disconnect
have not yet been closed and reopened.
.RE

.sp
.LP
The following code reads the device status device logical name:
.sp
.in +2
.nf
int fd;
int status;

if ((fd = open("/dev/usb/472.b0b0/0/devstat",
    O_RDONLY)) < 0)     {
        /* handle error */
}

if (read(fd, &status, sizeof(status))  != sizeof(status)) {
        /* handle error */
}

switch (status) {
case USB_DEV_STAT_DISCONNECTED:
        printf ("Terminating as device has been disconnected.\en");
        exit (0);

case USB_DEV_STAT_RESUMED:
case USB_DEV_STAT_UNAVAILABLE:
        /*
         * Close and reopen endpoints to reestablish device access,
         * then reset device.
         */
        break;

case USB_DEV_STAT_ONLINE:
default:
        break;
}
.fi
.in -2

.sp
.LP
Use \fBpoll\fR(2) to block on several logical names simultaneously, including
device status logical names.  Poll indicates when reading a logical name would
return data. See \fBpoll\fR(2) for details. Calls to read may be done whether
or not they follow calls to poll.
.SH ENDPOINT STATUS MANAGEMENT
.sp
.LP
Each data endpoint has a corresponding status logical name. Use the status
logical name to retrieve the state of the data endpoint, including detail on
how its most recent transfer failed. Reads of the status file descriptors
always return immediately. See the ERRORS section for more information on
endpoint status values. All logical device name files created for returning
status must be opened with \fBO_RDONLY\fR.
.sp
.LP
The following code illustrates reading the status file descriptor of an
endpoint which just failed a data transfer in order to get more information on
the failure.
.sp
.in +2
.nf
int data_xfered, status;
int ep1_data_fd, ep1_stat_fd;
uchar_t request[8];

ep1_data_fd = open ("/dev/usb/472.b0b0/0/if0out1", O_WRONLY);

if (ep1_data_fd < 0) {
        /* Handle open error. */
}

ep1_stat_fd = open ("/dev/usb/472.b0b0/0/if0out1stat",
    O_RDONLY);
if (ep1_stat_fd < 0) {
        /* Handle open error. */
}

data_xfered = write(ep1_data_fd, request, sizeof (request));

/* An error occured during the data transfer. */
if (data_xfered != sizeof (request)) {

        /* Read status file descriptor for details on failure. */
        if (read(ep1_stat_fd, (int *)&status, sizeof (status)) !=
            sizeof (status)) {
                status = USB_LC_STAT_UNSPECIFIED_ERR;
        }

        /* Take appropriate action. */
        switch (status) {
        case USB_LC_STAT_STALL:
                printf ("Endpoint stalled.\en");
                break;
        case ...
                ...
        }

   }
.fi
.in -2

.SH CONTROL TRANSFERS
.sp
.LP
The control endpoint is typically used to set up the device and to query device
status or configuration.
.sp
.LP
Applications requiring I/O on a control endpoint should open the corresponding
logical device name and use regular UNIX I/O system calls. For example:
\fBread\fR(2), \fBwrite\fR(2), \fBaioread\fR(3C) and \fBaiowrite\fR(3C).
\fBpoll\fR(2) is not supported on control endpoints.
.sp
.LP
A control endpoint must be opened with \fBO_RDWR\fR since it is bidirectional.
It cannot be opened with \fBO_NONBLOCK\fR or \fBO_NDELAY\fR.
.sp
.LP
For example:
.sp
.in +2
.nf
fd = open("/dev/usb/472.b0b0/0/cntrl0", O_RDWR);
        
.fi
.in -2

.sp
.in +2
.nf
fdstat = open("/dev/usb/472.b0b0/0/cntrl0stat", O_RDONLY);
.fi
.in -2

.sp
.LP
Control endpoints can be read and written. A \fBread\fR operation receives data
\fBfrom\fR the device and a \fBwrite\fR operation sends data \fBto\fR the
device.
.sp
.LP
To perform a control-IN transfer, perform a \fBwrite\fR(2) of USB setup data
(see section 9.3 of the \fIUSB 1.1\fR or \fI2.0\fR specifications) followed by
a \fBread\fR(2) on the same control endpoint to fetch the desired data. For
example:
.sp
.in +2
.nf
void init_cntrl_req(
    uchar_t *req, uchar_t bmRequestType, uchar_t bRequest,
    ushort_t wValue, ushort_t wIndex, ushort_t wLength) {
        req[0] = bmRequestType;
        req[1] = bRequest;
        req[2] = 0xFF & wValue;
        req[3] = 0xFF & (wValue >> 8);
        req[4] = 0xFF & wIndex;
        req[5] = 0xFF & (wIndex >> 8);
        req[6] = 0xFF & wLength;
        req[7] = 0xFF & (wLength >> 8);
 }

 ....


        uchar_t dev_descr_req[8];
        usb_dev_descr_t descr;

        init_cntrl_req(dev_descr_req,
            USB_DEV_REQ_DEV_TO_HOST, USB_REQ_GET_DESCR,
            USB_DESCR_TYPE_SETUP_DEV, 0, sizeof (descr));

        count = write(fd, dev_descr_req, sizeof (dev_descr_req));
        if (count != sizeof (dev_descr_req)) {
                /* do some error recovery */
                ...
        }

        count = read(fd, &descr, sizeof (descr));
        if (count != sizeof (descr)) {
                /* do some error recovery */
        }
.fi
.in -2

.sp
.LP
The application can issue any number of reads to read data received on a
control endpoint. \fBugen\fR successfully completes all reads, returning the
number of bytes transferred. Zero is returned when there is no data to
transfer.
.sp
.LP
If the \fBread\fR/\fBwrite\fR fails and returns \fB-1\fR, you can access the
endpoint's status device logical name for precise error information:
.sp
.in +2
.nf
        int status;

        count = read(fdstat, &status, sizeof (status));
        if (count == sizeof (status)) {
                switch (status) {
                case USB_LC_STAT_SUSPENDED:
                case USB_LC_STAT_DISCONNECTED:
                        /* close all endpoints */
                        ...
                        break;
                default:
                        ...
                        break;
                }
        }
.fi
.in -2

.sp
.LP
Refer to the ERRORS section for all possible error values.
.sp
.LP
To perform a control-OUT transfer, send in a single transfer, the USB setup
data followed by any accompanying data bytes.
.sp
.in +2
.nf
    /* 1st 8 bytes of wbuf are setup. */
    init_cntrl_req(wbuf, .......);

    /* Data bytes begin at byte 8 of wbuf. */
    bcopy(data, &wuf[8], sizeof (data));

    /* Send it all in a single transfer. */
    count = write(fd, wbuf, sizeof (wbuf));
.fi
.in -2

.sp
.LP
A \fBwrite\fR(2) returns the number of bytes (both setup and data) actually
transferred, (whether or not the \fBwrite\fR is completely successful),
provided that some data is actually transferred. When no data is transferred,
\fBwrite\fR(2) returns \fB-1\fR. Applications can read the corresponding
endpoint status to retrieve detailed error information. Note that it is an
error to specify a size different than:
.sp
.LP
(number of data bytes + number of setup bytes).
.sp
.LP
Here is a more extensive example which gets all descriptors of a device
configuration.  For sake of brevity, uninteresting parts are omitted.
.sp
.in +2
.nf
   #include <sys/usb/usba.h>
   #include <sys/usb/clients/ugen/usb_ugen.h>

   uchar_t *config_cloud;
   uchar_t *curr_descr;

   uchar_t *bytes;
  
   int curr_descr_len;
   int curr_descr_type;
   
   usb_cfg_descr_t cfg_descr;
   usb_if_descr_t if_descr;
   usb_ep_descr_t ep_descr;
  
   /* See 9.13 of USB 2.0 spec for ordering. */
   static char *pipetypes[] = {
        "Control", "Isochronous", "Bulk", "Interrupt"
   };
  
   /*
    * Setup to send a request to read just the config descriptor.  The
    * size of the whole cloud, containing all cfg, interface, endpoint,
    * class and vendor-specific descriptors, will be returned as part of
    * the config descriptor.
    */
   init_cntrl_req(&setup_data, USB_DEV_REQ_DEV_TO_HOST, USB_REQ_GET_DESCR,
                   USB_DESCR_TYPE_SETUP_CFG, 0, USB_CFG_DESCR_SIZE);
   
   /*
    * Write setup data. USB device will prepare to return the whole
    * config cloud as a response to this. We will read this separately.
    */
   count = write(ctrl_fd, &setup_data, sizeof (setup_data));
   if (count != sizeof (setup_data)) {
            /* Error recovery. */
   } else {
           count = read(ctrl_fd, &cfg_descr, USB_CFG_DESCR_SIZE);
           if (count != USB_CFG_DESCR_SIZE) {
                    /* Error recovery. */
           }
   }
   
   /* USB data is little endian. */
   bytes = (uchar_t *)(&cfg_descr.wTotalLength);
   totalLength = bytes[0] + (bytes[1] << 8);
   
   /*
    * The size of the whole cloud is in the bLength field.  Set up
    * to read this amount of data, to get the whole cloud.
    */
   config_cloud = malloc(totalLength);
   
   init_cntrl_req(&setup_data, USB_DEV_REQ_DEV_TO_HOST, USB_REQ_GET_DESCR,
                   USB_DESCR_TYPE_SETUP_CFG, 0, totalLength);
   
   count = write(ctrl_fd, &setup_data, sizeof (setup_data));                                                                                          	   
   if (count != sizeof (setup_data)) {
           /* Error recovery. */
   } else {
           count = read(ctrl_fd, config_cloud, totalLength);
           if (count != totalLength) {
                   /* Error recovery. */
            }
   }
   
   /* Got the data.  Now loop, dumping out the descriptors found. */
   
   curr_descr = config_cloud;
   offset = 0;
   while (offset < totalLength) {
   
           /* All descr have length and type at offset 0 and 1 */
           curr_descr_len = curr_descr[0];
           curr_descr_type = curr_descr[1];
           
           switch (curr_descr_type) {
           case USB_DESCR_TYPE_CFG:
           
                    /*
                     * Copy data into separate structure, needed for                                                                   
                     * proper alignment of all non char fields.  Note:
                     * non-char fields of all descriptors begin on aligned
                     * boundaries.  The issue is that some structures may
                     * be adjacent to others which have an odd-numbered
                     * byte size, and may thus start on an odd-numbered
                     * boundary.  */
                    bcopy(curr_descr, &cfg_descr, curr_descr_len);    

                    /* Remember to read any words in endian-neutral way. */
                    
                    (void) printf("\enConfig %d found.\en",
                        cfg_descr.bConfigurationValue);
                    break;
                     
            case USB_DESCR_TYPE_IF:
                    bcopy(curr_descr, &if_descr, curr_descr_len);
                    (void) printf("\en\etInterface %d, Alt %d found.\en",
                        if_descr.bInterfaceNumber,
                        if_descr.bAlternateSetting);
                    break;
                  
            case USB_DESCR_TYPE_EP:
                    bcopy(curr_descr, &ep_descr, curr_descr_len);
                    (void) printf("\en\et\etEndpoint %d (%s-%s) found.\en",
                        (ep_descr.bEndpointAddress & USB_EP_NUM_MASK),
                        (pipetypes[
                            ep_descr.bmAttributes & USB_EP_ATTR_MASK]),
                        ((ep_descr.bEndpointAddress &
                        USB_EP_DIR_IN) ? "IN" : "OUT"));
                     break;

             default:
                     (void) printf(
                         "\en\et\et\etOther descriptor found.  Type:%d\en",
                         curr_descr_type);
                     break;
             }
             
             offset += curr_descr_len;
             curr_descr = &config_cloud[offset];
   }
.fi
.in -2

.SH INTERRUPT-IN TRANSFERS
.sp
.LP
Applications requiring data from an interrupt-IN endpoint should open the
corresponding logical device name and use \fBread\fR(2), \fBaioread\fR(3C) and
\fBpoll\fR(2) system calls.
.sp
.LP
An interrupt-IN endpoint must be opened with \fBO_RDONLY\fR. It can also be
opened using \fBO_NONBLOCK\fR or \fBO_NDELAY\fR if desired.
.sp
.in +2
.nf
fd = open("/dev/usb/472.b0b0/0/if0in1", O_RDONLY);
.fi
.in -2

.sp
.in +2
.nf
fdstat = open("/dev/usb/472.b0b0/0/if0in1stat", O_RDONLY);
    
.fi
.in -2

.sp
.LP
\fBugen\fR starts polling interrupt\(emIN endpoints immediately upon opening
them and stops polling them upon closure. (Polling refers to interrogation of
the device by the driver and should not be confused with \fBpoll\fR(2), which
is an interrogation of the driver by the application.)
.sp
.LP
A \fBread\fR(2) of an endpoint opened with the \fBO_NONBLOCK\fR or
\fBO_NDELAY\fR flags set will not block when there is insufficient data
available to satisfy the request. The \fBread\fR simply returns what it can
without signifying any error.
.sp
.LP
Applications should continuously check for and consume interrupt data.
\fBugen\fR enables buffering of up to one second of incoming data. In case of
buffer overflow, \fBugen\fR stops polling the interrupt-IN endpoint until the
application consumes all the data. In this case, a \fBread\fR(2) of an empty
buffer returns \fB-1\fR, sets the endpoint status to
\fBUSB_LC_STAT_INTR_BUF_FULL\fR (to indicate that the buffer had been full and
polling had been stopped) and causes \fBugen\fR to start polling the endpoint
again. To retrieve the status, the application can open and read the
corresponding endpoint's status device logical name.
.sp
.in +2
.nf
for (;;) {
        count = read(fd, buf, sizeof(buf));
        if (count == -1) {
                int cnt, status;

                cnt = read(fdstat, &status, sizeof (status));
                if (cnt == -1) {
                         /* more error recovery here */
                } else {
                        switch (status) {
                        case USB_LC_STAT_INTR_BUF_FULL:
                               ...
                               break;
                        default:
                               ...
                               break;
                        }
                }
           }
           /* process the data */
           ....
        }
.fi
.in -2

.sp
.LP
\fBugen\fR will never drop data. However, the device may drop data if the
application cannot read it at the rate that it is produced.
.sp
.LP
Applications requiring unbuffered data from an interrupt-IN endpoint should
open the associated status endpoint with O_RDWR before opening the associated
interrupt-IN endpoint and write a control byte with USB_EP_INTR_ONE_XFER set.
All other bits are reserved and should be 0.
.sp
.LP
"One transfer" mode will persist until disabled explicitly after the associated
interrupt-IN endpoint has been closed by writing a control byte with
USB_EP_INTR_ONE_XFER cleared.
.sp
.LP
"One transfer" mode is implicitly disabled when the status/control endpoint is
closed.
.sp
.LP
Attempts to change the "one transfer" mode while the endpoint is open will
result in \fBEINVAL\fR.
.sp
.LP
An application can open multiple interrupt-IN endpoints and can call
\fBpoll\fR(2) to monitor the availability of new data. (Note: poll works with
interrupt-IN data endpoints, not their status endpoints.)
.sp
.in +2
.nf
        struct pollfd pfd[2];

        bzero(pfd, sizeof (pfd));
        pfd[0].fd = fd1;    /* fd1 is one interrupt-IN endpoint. */
        pfd[0].events = POLLIN;
        pfd[1].fd = fd2;    /* fd2 is another interrupt-IN endpoint. */
        pfd[1].events = POLLIN;

        for (;;) {
                poll(pfd, 2, -1);

                if (pfd[0].revents & POLLIN) {
                        count = read(fd1, buf, sizeof (buf));
                        ....
                } 
                if (pfd[1].revents & POLLIN) {
                        count = read(fd2, buf, sizeof (buf));
                        ....
                } 
        }
.fi
.in -2

.sp
.LP
You can monitor the device status endpoint via \fBpoll\fR(2) concurrently with
the multiple interrupt-IN endpoints.  Simply add another pollfd element to the
pfd array in the previous code example, and initialize the new element's
\fBfd\fR field with the file  descriptor  of the device status endpoint (opened
without O_NONBLOCK  or  O_NDELAY).  Set the new element's event field to POLLIN
like the other elements. Note that only interrupt-IN endpoints and the device
status endpoint can be monitored using \fBpoll\fR(2).
.SH INTERRUPT-OUT TRANSFERS
.sp
.LP
Applications requiring output on an interrupt-OUT endpoint can open the
corresponding  logical  device name and perform regular UNIX I/O  system calls
such as \fBwrite\fR(2) and \fBaiowrite\fR(3C).
.sp
.LP
An interrupt-OUT endpoint must be opened with O_WRONLY.
.sp
.in +2
.nf
fd = open("/dev/usb/472.b0b0/0/if0out3", O_WRONLY);

fdstat = open("/dev/usb/472.b0b0/0/if0out3stat", O_RDONLY);

       
.fi
.in -2

.sp
.LP
Data can be written to an interrupt-OUT endpoint as follows:
.sp
.in +2
.nf
      count = write(fd, buf, sizeof (buf)):
      if (count == -1) {
             /* error recovery */
      }
.fi
.in -2

.SH BULK TRANSFERS
.sp
.LP
Applications requiring I/O on a bulk endpoint can open the corresponding
logical device name and perform regular UNIX I/O system calls. For example:
\fBread\fR(2), \fBwrite\fR(2), \fBaioread\fR(3C) and \fBaiowrite\fR(3C).
\fBpoll\fR(2) is not supported on bulk endpoints.
.sp
.LP
A bulk endpoint must be opened with \fBO_RDONLY\fR or \fBO_WRONLY\fR and cannot
be opened with \fBO_NONBLOCK\fR or \fBO_NDELAY:\fR
.sp
.in +2
.nf
fd = open("/dev/usb/472.b0b0/0/if0in2", O_RDONLY);
.fi
.in -2

.sp
.in +2
.nf
fdstat = open("/dev/usb/472.b0b0/0/if0in2stat", O_RDONLY);
.fi
.in -2

.sp
.LP
Data can be read from a bulk-IN endpoint as follows:
.sp
.in +2
.nf
        count = read(fd, buf, sizeof (buf)):
        if (count == -1) {
                /* error recovery */
        }

 Data can be written to a bulk-OUT endpoint as follows:

        count = write(fd, buf, sizeof (buf)):
        if (count == -1) {
                /* error recovery */
        }
.fi
.in -2

.SH ISOCHRONOUS TRANSFERS
.sp
.LP
Applications requiring I/O on an isochronous endpoint can open the
corresponding logical device name and perform regular UNIX I/O system calls
such as \fBread\fR(2), \fBwrite\fR(2), \fBpoll\fR(2), \fBaioread\fR(3C) and
\fBaiowrite\fR(3C). An isochronous endpoint must be opened with \fBO_RDWR\fR.
.sp
.in +2
.nf
fd = open("/dev/usb/472.b0b0/0/if0.3in2", O_RDWR);

fdstat = open("/dev/usb/472.b0b0/0/if0.3in2stat", O_RDONLY);
.fi
.in -2

.sp
.LP
Applications can use the status logical name to retrieve the state of the
isochronous data endpoint, including details on why the most recent transfer
failed.
.sp
.LP
Applications have the flexibility to specify the number of isochronous packets
and the size of individual packets they want to transfer. Applications should
use the following data structures to exchange isochronous packet information
with the \fBugen\fR driver:
.sp
.in +2
.nf
typedef struct ugen_isoc_pkt_descr {
		/*
		* Set by the application, for all isochro.
		* requests, to the num. of bytes to xfer
		* in a packet.
		*/
 	      ushort_t        dsc_isoc_pkt_len;
 
		/*         
		* Set by ugen to actual num. of bytes sent/received
		* in a packet.
			*/
       ushort_t        dsc_isoc_pkt_actual_len;
 
		/*
		* Per pkt. status set by ugen driver both for the
		* isochronous IN and OUT requests. Application can
		* use USB_LC_STAT_* to parse the status.
		*/
      int     dsc_isoc_pkt_status;
 } ugen_isoc_pkt_descr_t; 
      
 typedef struct ugen_isoc_req_head {
   /* pkt count of the isoc request */
    int req_isoc_pkts_count;
 
  /* pkt descriptors */
  ugen_isoc_pkt_descr_t req_isoc_pkt_descrs[1]; 
 } ugen_isoc_req_head_t;
.fi
.in -2

.sp
.LP
\fBreq_isoc_pkts_count\fR is limited by the capability of the USB host
controller driver. The current upper bound for the \fBuhci\fR and \fBohci\fR
drivers is 512. The upper bound for the \fBehci\fR driver is 1024.
.sp
.LP
For an isochronous-IN endpoint, applications must first use the
\fBugen_isoc_req_head_t\fR structure followed by \fBugen_isoc_pkt_descr_t\fR to
write packet request information to the \fBugen\fR node. The \fBugen\fR driver
then checks the validity of the request. If it is valid, the driver immediately
begins isochronous polling on the IN endpoint and applications can proceed with
\fBread\fR(2) of the data on the isochronous-IN endpoint. Upon successful
return of \fBread\fR(2), isochronous packet descriptors (whose
\fBdsc_isoc_pkt_actual_len\fR and \fBdsc_isoc_pkt_status\fR fields were filled
by the driver) are returned, followed by the request's device payload data.
.sp
.LP
Applications should continuously check for and consume isochronous data. The
\fBugen\fR driver enables buffering of up to eight seconds of incoming data for
full-speed isochronous endpoint, one second of data for high-speed isochronous
endpoints who request one transaction per microframe and 1/3 of a second of
incoming data for high-speed high-bandwidth isochronous endpoints who request
three transactions per microframe. In case of buffer overflow, \fBugen\fR
discards the oldest data.
.sp
.LP
The isochronous-IN polling can only be stopped by a \fBclose\fR(2) associated
file descriptor. If applications want to change packet information, they must
first \fBclose\fR(2) the endpoint to stop the isochronous-IN polling, then
\fBopen\fR(2) the endpoint and \fBwrite\fR(2) new packets request.
.sp
.LP
The following example shows how to read an isochronous-IN endpoint:
.sp
.in +2
.nf
		#include  <sys/usb/clients/ugen/usb_ugen.h>

		char *buf, *p;
		ushort_t  pktlen;
		int pktcnt, i;
		int len;
		ugen_isoc_req_head_t *req;
		ugen_isoc_pkt_descr_t *pktdesc;
		char rdbuf[5000];
 
		pktcnt = 4; /* 4 packets in this request */
 	
		len = sizeof(int) +
			sizeof(ugen_isoc_pkt_descr_t) * pktcount;
  
		buf = malloc(len);
		if (!buf) {
			/* Error recovery. */
 	    }
 
		req = (ugen_isoc_req_head_t *)buf;
		req->req_isoc_pkts_count = pktcnt;
 
		pktdesc = (ugen_isoc_pkt_descr_t *)
			(req->req_isoc_pkt_descrs);
 
     for (i = 0; i < pktcnt; i++) {
				/*
				* pktlen should not exceed xfer
				* capability of an endpoint
				*/
				pktdesc[i].dsc_isoc_pkt_len = pktlen; 
 
 				pktdesc[i].dsc_isoc_pkt_actual_len = 0;
				pktdesc[i].dsc_isoc_pkt_status = 0;
 	    }
 
			/*
			* write request info to driver and len must
			* be exactly the sum of
			* sizeof(int) + sizeof(ugen_isoc_pkt_descr_t) * pktcnt.
			* Otherwise, an error is returned.
			*/
			if (write(fd, buf, len) < 0) {
				/* Error recovery. */
 	    } 
 
			/*
			* Read length should be sum of all pkt descriptors
			* length + payload data length of all pkts
			* (sizeof(ugen_isoc_pkt_descr_t) + pktlen) * pktcnt
			*/
			if (read(fd, rdbuf, (sizeof(ugen_isoc_pkt_descr_t) +
 	        pktlen) * pktcnt) < 0) {
				/* Error recovery. */
 	    }
 
			pktdesc = (ugen_isoc_pkt_descr_t *) rdbuf;
 
			/* points to payload beginning */
			p = rdbuf + pktcnt * sizeof(ugen_isoc_pkt_descr_t);
 
			for (i = 0; i < pktcnt; i++) {
				printf("packet %d len = %d,"
					" actual_len = %d, status = 0x%x\n",
					i, pktdesc->dsc_isoc_pkt_len,
					pktdesc->dsc_isoc_pkt_actual_len,
					pktdesc->dsc_isoc_pkt_status);
 
				/* Processing data */
 
				/*
				* next packet data payload, do NOT use
				* dsc_isoc_pkt_actual_len
				*/
				p += pktdesc->dsc_isoc_pkt_len; 
 
				pktdesc++;
 }
.fi
.in -2

.sp
.LP
For an isochronous-OUT endpoint, applications use the same packet descriptor
and request structures to write request   information to the \fBugen\fR node.
Following the packet request head information is the packet payload data. Upon
successful return of \fBwrite\fR(2), applications can \fBread\fR(2) the same
\fBugen\fR file immediately to retrieve the individual packet transfer status
of the last request. If the application isn't concerned about the status, it
can omit it.
.sp
.LP
In the following example, an application transfers data on an isochronous-OUT
endpoint:
.sp
.in +2
.nf
		#include <sys/usb/clients/ugen/usb_ugen.h>
		char *buf, *p;
		ushort_t i, pktlen;
		int len, pktcnt;
		ugen_isoc_req_head_t *req;
		ugen_isoc_pkt_descr_t *pktdesc;
		char rdbuf[4096];
 
		pktcnt = 4;
 
		/*
		* set packet length to a proper value, don't
		* exceed endpoint's capability
		*/
		pktlen = 1024; 
 
		len = sizeof(int) +
			sizeof(ugen_isoc_pkt_descr_t) * pktcount;
 	    
		len += pktlen * pktcnt;
 
		buf = malloc(len);
		if (!buf) {
			/* Error recovery. */
 	    }
     
		req = (ugen_isoc_req_head_t *)buf;
		req->req_isoc_pkts_count = pktcnt;
 
		pktdesc =
			(ugen_isoc_pkt_descr_t *)(req->req_isoc_pkt_descrs);
 
		for (i = 0; i < pktcnt; i++) {
			pktdesc[i].dsc_isoc_pkt_len = pktlen;
			pktdesc[i].dsc_isoc_pkt_actual_len = 0;
			pktdesc[i].dsc_isoc_pkt_status = 0;
 	    }
 	
		/* moving to beginning of payload data */
		p = buf + sizeof(int) + sizeof(*pktdesc) * pktcnt;
		for (i = 0; i < pktcnt; i++) {
 
			/* fill in the data buffer */
 
			p += pktlen;
     }
 
		/*
		* write packet request information and data to ugen driver
		*
		* len should be the exact value of sizeof(int) +
		*    sizeof(ugen_isoc_pkt_descr_t) * pktcnt + payload length
		*/
		if (write(fd, buf, len) < 0) {
			/* Error recovery. */
 	    } 
 
		/* read packet status */
		if (read(fd, rdbuf, sizeof(*pktdesc) * pktcnt) < 0) {
 
			/* Error recovery. */
 
		} else {
 
			/* Parse every packet's transfer status */
 
  	    }
.fi
.in -2

.SH ERRORS
.sp
.LP
The following statuses are returned by endpoint status device logical names:
.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_NOERROR\fR
.ad
.sp .6
.RS 4n
No error.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_CRC\fR
.ad
.sp .6
.RS 4n
CRC error detected.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_BITSTUFFING\fR
.ad
.sp .6
.RS 4n
Bit stuffing error.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_DATA_TOGGLE_MM\fR
.ad
.sp .6
.RS 4n
Data toggle did not match.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_STALL\fR
.ad
.sp .6
.RS 4n
Endpoint returned stall.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_DEV_NOT_RESP\fR
.ad
.sp .6
.RS 4n
Device not responding.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_UNEXP_PID\fR
.ad
.sp .6
.RS 4n
Unexpected Packet Identifier (PID).
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_PID_CHECKFAILURE\fR
.ad
.sp .6
.RS 4n
Check bits on PID failed.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_DATA_OVERRUN\fR
.ad
.sp .6
.RS 4n
Data overrun.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_DATA_UNDERRUN\fR
.ad
.sp .6
.RS 4n
Data underrun.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_BUFFER_OVERRUN\fR
.ad
.sp .6
.RS 4n
Buffer overrun.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_BUFFER_UNDERRUN\fR
.ad
.sp .6
.RS 4n
Buffer underrun.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_TIMEOUT\fR
.ad
.sp .6
.RS 4n
Command timed out.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_NOT_ACCESSED\fR
.ad
.sp .6
.RS 4n
Not accessed by the hardware.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_UNSPECIFIED_ERR\fR
.ad
.sp .6
.RS 4n
Unspecified USBA or HCD error.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_NO_BANDWIDTH\fR
.ad
.sp .6
.RS 4n
No bandwidth available.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_HW_ERR\fR
.ad
.sp .6
.RS 4n
Host Controller h/w error.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_SUSPENDED\fR
.ad
.sp .6
.RS 4n
Device was suspended.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_DISCONNECTED\fR
.ad
.sp .6
.RS 4n
Device was disconnected.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_INTR_BUF_FULL\fR
.ad
.sp .6
.RS 4n
Polling was stopped as the interrupt-IN data buffer was full. Buffer is  now
empty and polling has been resumed.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_INTERRUPTED\fR
.ad
.sp .6
.RS 4n
Request was interrupted.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_NO_RESOURCES\fR
.ad
.sp .6
.RS 4n
No resources available for request.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_INTR_POLLING_FAILED\fR
.ad
.sp .6
.RS 4n
Failed to restart polling.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_ISOC_POLLING_FAILED\fR
.ad
.sp .6
.RS 4n
Failed to start isochronous polling.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_ISOC_UNINITIALIZED\fR
.ad
.sp .6
.RS 4n
Isochronous packet information not initialized.
.RE

.sp
.ne 2
.mk
.na
\fBUSB_LC_STAT_ISOC_PKT_ERROR\fR
.ad
.sp .6
.RS 4n
All packets in this isochronous request have errors. The polling on this
isochronous-IN endpoint is suspended and can be resumed on next \fBread\fR(2).
.RE

.sp
.LP
The following system call \fBerrno\fR values are returned:
.sp
.ne 2
.mk
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 11n
.rt  
An attempt was made to enable or disable "one transfer" mode while the
associated endpoint was open.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEBUSY\fR\fR
.ad
.RS 11n
.rt  
The endpoint has been opened and another open is attempted.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEACCES\fR\fR
.ad
.RS 11n
.rt  
An endpoint open was attempted with incorrect flags.
.RE

.sp
.ne 2
.mk
.na
\fB\fBENOTSUP\fR\fR
.ad
.RS 11n
.rt  
Operation not supported.
.RE

.sp
.ne 2
.mk
.na
\fB\fBENXIO\fR\fR
.ad
.RS 11n
.rt  
Device associated with the file descriptor does not exist.
.RE

.sp
.ne 2
.mk
.na
\fBENODEV\fR
.ad
.RS 11n
.rt  
Device has been hot-removed or a suspend/resume happened before this command.
.RE

.sp
.ne 2
.mk
.na
\fBEIO\fR
.ad
.RS 11n
.rt  
An I/O error occurred. Send a read on the endpoint status minor node to get the
exact error information.
.RE

.sp
.ne 2
.mk
.na
\fBEINTR\fR
.ad
.RS 11n
.rt  
Interrupted system call.
.RE

.sp
.ne 2
.mk
.na
\fBENOMEM\fR
.ad
.RS 11n
.rt  
No memory for the allocation of internal structures.
.RE

.SH FILES
.sp
.in +2
.nf
        /kernel/drv/ugen   32 bit ELF kernel module (x86 platform only)
        /kernel/drv/sparcv9/ugen   64 bit ELF kernel module

        /dev/usb/<vid>.<pid>/<N>/cntrl0
        /dev/usb/<vid>.<pid>/<N>/cntrl0stat

        /dev/usb/<vid>.<pid>/<N>/if<interface#>
                                <in|out|cntrl><endpoint#>
        /dev/usb/<vid>.<pid>/<N>/if<interface#>
                                <in|out|cntrl><endpoint#>stat

        /dev/usb/<vid>.<pid>/<N>/if<interface#>.
                                <alternate><in|out|cntrl<endpoint#>
        /dev/usb/<vid>.<pid>/<N>/if<interface#>.
                                <alternate><in|out|cntrl><endpoint#>stat

        /dev/usb/<vid>.<pid>/<N>/cfg<value>if<interface#>
                                <in|out|cntrl><endpoint#>
        /dev/usb/<vid>.<pid>/<N>/cfg<value>if<interface#>
                                <in|out|cntrl<endpoint#stat>

        /dev/usb/<vid>.<pid>/<N>/cfg<value>if<interface#>.
                                <alternate><in|out|cntrl><endpoint#>
        /dev/usb/<vid>.<pid>/<N>/cfg<value>if<interface#>.
                                <alternate><in|out|cntrl><endpoint#>stat


        /dev/usb/<vid>.<pid>/<N>/devstat

        /dev/usb/<vid>.<pid>/<N>/if<interface#>cntrl0
        /dev/usb/<vid>.<pid>/<N>/if<interface#>cntrl0stat
.fi
.in -2

.sp
.LP
where \fIN\fR is an integer representing the instance number of this type of
device. (All logical device names for a single device share the same \fIN\fR.)
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
ArchitecturePCI-based  SPARC
.TE

.SH SEE ALSO
.sp
.LP
\fBlibusb\fR(3LIB), \fBclose\fR(2), \fBpoll\fR(2), \fBread\fR(2),
\fBwrite\fR(2), \fBaioread\fR(3C), \fBaiowrite\fR(3C), \fBusba\fR(7D),
\fBusb_dev_descr\fR(9S).
.SH DIAGNOSTICS
.sp
.LP
In addition to being logged, the following messages may appear on the system
console. All messages are formatted in the following manner:
.sp
.in +2
.nf
Warning: <device path> (ugen<instance num>): Error Message...
.fi
.in -2
.sp

.sp
.ne 2
.mk
.na
\fBToo many minor nodes. \fR
.ad
.sp .6
.RS 4n
Device has too many minor nodes. Not all are available.
.RE

.sp
.ne 2
.mk
.na
\fBInstance number too high (<\fInumber\fR>).\fR
.ad
.sp .6
.RS 4n
Too many devices are using this driver.
.RE

.sp
.ne 2
.mk
.na
\fBCannot access <device>.  Please reconnect.\fR
.ad
.sp .6
.RS 4n
This device has been disconnected because a device other than the original one
has been inserted. The driver informs you of this fact by displaying the name
of the original device.
.RE

.sp
.ne 2
.mk
.na
\fBDevice is not identical to the previous one on this port. Please disconnect
and reconnect.\fR
.ad
.sp .6
.RS 4n
Same condition as described above; however in this case, the driver is unable
to identify the original device with a name string.
.RE

.SH NOTES
.sp
.LP
\fBugen\fR returns \fB-1\fR for all commands and sets \fBerrno\fR to
\fBENODEV\fR when device has been hot-removed or resumed from a suspend. The
application must close and reopen all open minor nodes to reinstate successful
communication.