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USB: g_file_storage: add CD-ROM emulation
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This patch (as1172) adds the ability to emulate a CD-ROM drive to
g_file_storage.  The emulation is limited, since it presents as a disc
containing a single data track and no audio tracks.  Still, it may
come in useful on occasion.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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Alan Stern authored and Greg Kroah-Hartman committed Jan 7, 2009
1 parent dbe6e0c commit 12aae68
Showing 1 changed file with 154 additions and 22 deletions.
176 changes: 154 additions & 22 deletions drivers/usb/gadget/file_storage.c
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
/*
* file_storage.c -- File-backed USB Storage Gadget, for USB development
*
* Copyright (C) 2003-2007 Alan Stern
* Copyright (C) 2003-2008 Alan Stern
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
Expand Down Expand Up @@ -38,16 +38,17 @@

/*
* The File-backed Storage Gadget acts as a USB Mass Storage device,
* appearing to the host as a disk drive. In addition to providing an
* example of a genuinely useful gadget driver for a USB device, it also
* illustrates a technique of double-buffering for increased throughput.
* Last but not least, it gives an easy way to probe the behavior of the
* Mass Storage drivers in a USB host.
* appearing to the host as a disk drive or as a CD-ROM drive. In addition
* to providing an example of a genuinely useful gadget driver for a USB
* device, it also illustrates a technique of double-buffering for increased
* throughput. Last but not least, it gives an easy way to probe the
* behavior of the Mass Storage drivers in a USB host.
*
* Backing storage is provided by a regular file or a block device, specified
* by the "file" module parameter. Access can be limited to read-only by
* setting the optional "ro" module parameter. The gadget will indicate that
* it has removable media if the optional "removable" module parameter is set.
* setting the optional "ro" module parameter. (For CD-ROM emulation,
* access is always read-only.) The gadget will indicate that it has
* removable media if the optional "removable" module parameter is set.
*
* The gadget supports the Control-Bulk (CB), Control-Bulk-Interrupt (CBI),
* and Bulk-Only (also known as Bulk-Bulk-Bulk or BBB) transports, selected
Expand All @@ -64,7 +65,12 @@
* The default number of LUNs is taken from the number of "file" elements;
* it is 1 if "file" is not given. If "removable" is not set then a backing
* file must be specified for each LUN. If it is set, then an unspecified
* or empty backing filename means the LUN's medium is not loaded.
* or empty backing filename means the LUN's medium is not loaded. Ideally
* each LUN would be settable independently as a disk drive or a CD-ROM
* drive, but currently all LUNs have to be the same type. The CD-ROM
* emulation includes a single data track and no audio tracks; hence there
* need be only one backing file per LUN. Note also that the CD-ROM block
* length is set to 512 rather than the more common value 2048.
*
* Requirements are modest; only a bulk-in and a bulk-out endpoint are
* needed (an interrupt-out endpoint is also needed for CBI). The memory
Expand All @@ -91,6 +97,8 @@
* USB device controller (usually true),
* boolean to permit the driver to halt
* bulk endpoints
* cdrom Default false, boolean for whether to emulate
* a CD-ROM drive
* transport=XXX Default BBB, transport name (CB, CBI, or BBB)
* protocol=YYY Default SCSI, protocol name (RBC, 8020 or
* ATAPI, QIC, UFI, 8070, or SCSI;
Expand All @@ -103,15 +111,16 @@
* PAGE_CACHE_SIZE)
*
* If CONFIG_USB_FILE_STORAGE_TEST is not set, only the "file", "ro",
* "removable", "luns", and "stall" options are available; default values
* are used for everything else.
* "removable", "luns", "stall", and "cdrom" options are available; default
* values are used for everything else.
*
* The pathnames of the backing files and the ro settings are available in
* the attribute files "file" and "ro" in the lun<n> subdirectory of the
* gadget's sysfs directory. If the "removable" option is set, writing to
* these files will simulate ejecting/loading the medium (writing an empty
* line means eject) and adjusting a write-enable tab. Changes to the ro
* setting are not allowed when the medium is loaded.
* setting are not allowed when the medium is loaded or if CD-ROM emulation
* is being used.
*
* This gadget driver is heavily based on "Gadget Zero" by David Brownell.
* The driver's SCSI command interface was based on the "Information
Expand Down Expand Up @@ -261,7 +270,7 @@

#define DRIVER_DESC "File-backed Storage Gadget"
#define DRIVER_NAME "g_file_storage"
#define DRIVER_VERSION "7 August 2007"
#define DRIVER_VERSION "20 November 2008"

static const char longname[] = DRIVER_DESC;
static const char shortname[] = DRIVER_NAME;
Expand Down Expand Up @@ -341,6 +350,7 @@ static struct {

int removable;
int can_stall;
int cdrom;

char *transport_parm;
char *protocol_parm;
Expand All @@ -359,6 +369,7 @@ static struct {
.protocol_parm = "SCSI",
.removable = 0,
.can_stall = 1,
.cdrom = 0,
.vendor = DRIVER_VENDOR_ID,
.product = DRIVER_PRODUCT_ID,
.release = 0xffff, // Use controller chip type
Expand All @@ -382,6 +393,9 @@ MODULE_PARM_DESC(removable, "true to simulate removable media");
module_param_named(stall, mod_data.can_stall, bool, S_IRUGO);
MODULE_PARM_DESC(stall, "false to prevent bulk stalls");

module_param_named(cdrom, mod_data.cdrom, bool, S_IRUGO);
MODULE_PARM_DESC(cdrom, "true to emulate cdrom instead of disk");


/* In the non-TEST version, only the module parameters listed above
* are available. */
Expand Down Expand Up @@ -411,6 +425,10 @@ MODULE_PARM_DESC(buflen, "I/O buffer size");

/*-------------------------------------------------------------------------*/

/* SCSI device types */
#define TYPE_DISK 0x00
#define TYPE_CDROM 0x05

/* USB protocol value = the transport method */
#define USB_PR_CBI 0x00 // Control/Bulk/Interrupt
#define USB_PR_CB 0x01 // Control/Bulk w/o interrupt
Expand Down Expand Up @@ -487,6 +505,8 @@ struct interrupt_data {
#define SC_READ_12 0xa8
#define SC_READ_CAPACITY 0x25
#define SC_READ_FORMAT_CAPACITIES 0x23
#define SC_READ_HEADER 0x44
#define SC_READ_TOC 0x43
#define SC_RELEASE 0x17
#define SC_REQUEST_SENSE 0x03
#define SC_RESERVE 0x16
Expand Down Expand Up @@ -2006,23 +2026,28 @@ static int do_inquiry(struct fsg_dev *fsg, struct fsg_buffhd *bh)
u8 *buf = (u8 *) bh->buf;

static char vendor_id[] = "Linux ";
static char product_id[] = "File-Stor Gadget";
static char product_disk_id[] = "File-Stor Gadget";
static char product_cdrom_id[] = "File-CD Gadget ";

if (!fsg->curlun) { // Unsupported LUNs are okay
fsg->bad_lun_okay = 1;
memset(buf, 0, 36);
buf[0] = 0x7f; // Unsupported, no device-type
buf[4] = 31; // Additional length
return 36;
}

memset(buf, 0, 8); // Non-removable, direct-access device
memset(buf, 0, 8);
buf[0] = (mod_data.cdrom ? TYPE_CDROM : TYPE_DISK);
if (mod_data.removable)
buf[1] = 0x80;
buf[2] = 2; // ANSI SCSI level 2
buf[3] = 2; // SCSI-2 INQUIRY data format
buf[4] = 31; // Additional length
// No special options
sprintf(buf + 8, "%-8s%-16s%04x", vendor_id, product_id,
sprintf(buf + 8, "%-8s%-16s%04x", vendor_id,
(mod_data.cdrom ? product_cdrom_id :
product_disk_id),
mod_data.release);
return 36;
}
Expand Down Expand Up @@ -2101,6 +2126,75 @@ static int do_read_capacity(struct fsg_dev *fsg, struct fsg_buffhd *bh)
}


static void store_cdrom_address(u8 *dest, int msf, u32 addr)
{
if (msf) {
/* Convert to Minutes-Seconds-Frames */
addr >>= 2; /* Convert to 2048-byte frames */
addr += 2*75; /* Lead-in occupies 2 seconds */
dest[3] = addr % 75; /* Frames */
addr /= 75;
dest[2] = addr % 60; /* Seconds */
addr /= 60;
dest[1] = addr; /* Minutes */
dest[0] = 0; /* Reserved */
} else {
/* Absolute sector */
put_be32(dest, addr);
}
}

static int do_read_header(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
struct lun *curlun = fsg->curlun;
int msf = fsg->cmnd[1] & 0x02;
u32 lba = get_be32(&fsg->cmnd[2]);
u8 *buf = (u8 *) bh->buf;

if ((fsg->cmnd[1] & ~0x02) != 0) { /* Mask away MSF */
curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
return -EINVAL;
}
if (lba >= curlun->num_sectors) {
curlun->sense_data = SS_LOGICAL_BLOCK_ADDRESS_OUT_OF_RANGE;
return -EINVAL;
}

memset(buf, 0, 8);
buf[0] = 0x01; /* 2048 bytes of user data, rest is EC */
store_cdrom_address(&buf[4], msf, lba);
return 8;
}


static int do_read_toc(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
struct lun *curlun = fsg->curlun;
int msf = fsg->cmnd[1] & 0x02;
int start_track = fsg->cmnd[6];
u8 *buf = (u8 *) bh->buf;

if ((fsg->cmnd[1] & ~0x02) != 0 || /* Mask away MSF */
start_track > 1) {
curlun->sense_data = SS_INVALID_FIELD_IN_CDB;
return -EINVAL;
}

memset(buf, 0, 20);
buf[1] = (20-2); /* TOC data length */
buf[2] = 1; /* First track number */
buf[3] = 1; /* Last track number */
buf[5] = 0x16; /* Data track, copying allowed */
buf[6] = 0x01; /* Only track is number 1 */
store_cdrom_address(&buf[8], msf, 0);

buf[13] = 0x16; /* Lead-out track is data */
buf[14] = 0xAA; /* Lead-out track number */
store_cdrom_address(&buf[16], msf, curlun->num_sectors);
return 20;
}


static int do_mode_sense(struct fsg_dev *fsg, struct fsg_buffhd *bh)
{
struct lun *curlun = fsg->curlun;
Expand Down Expand Up @@ -2848,6 +2942,26 @@ static int do_scsi_command(struct fsg_dev *fsg)
reply = do_read_capacity(fsg, bh);
break;

case SC_READ_HEADER:
if (!mod_data.cdrom)
goto unknown_cmnd;
fsg->data_size_from_cmnd = get_be16(&fsg->cmnd[7]);
if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
(3<<7) | (0x1f<<1), 1,
"READ HEADER")) == 0)
reply = do_read_header(fsg, bh);
break;

case SC_READ_TOC:
if (!mod_data.cdrom)
goto unknown_cmnd;
fsg->data_size_from_cmnd = get_be16(&fsg->cmnd[7]);
if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
(7<<6) | (1<<1), 1,
"READ TOC")) == 0)
reply = do_read_toc(fsg, bh);
break;

case SC_READ_FORMAT_CAPACITIES:
fsg->data_size_from_cmnd = get_be16(&fsg->cmnd[7]);
if ((reply = check_command(fsg, 10, DATA_DIR_TO_HOST,
Expand Down Expand Up @@ -2933,6 +3047,7 @@ static int do_scsi_command(struct fsg_dev *fsg)
// Fall through

default:
unknown_cmnd:
fsg->data_size_from_cmnd = 0;
sprintf(unknown, "Unknown x%02x", fsg->cmnd[0]);
if ((reply = check_command(fsg, fsg->cmnd_size,
Expand Down Expand Up @@ -3498,6 +3613,7 @@ static int open_backing_file(struct lun *curlun, const char *filename)
struct inode *inode = NULL;
loff_t size;
loff_t num_sectors;
loff_t min_sectors;

/* R/W if we can, R/O if we must */
ro = curlun->ro;
Expand Down Expand Up @@ -3541,8 +3657,19 @@ static int open_backing_file(struct lun *curlun, const char *filename)
rc = (int) size;
goto out;
}
num_sectors = size >> 9; // File size in 512-byte sectors
if (num_sectors == 0) {
num_sectors = size >> 9; // File size in 512-byte blocks
min_sectors = 1;
if (mod_data.cdrom) {
num_sectors &= ~3; // Reduce to a multiple of 2048
min_sectors = 300*4; // Smallest track is 300 frames
if (num_sectors >= 256*60*75*4) {
num_sectors = (256*60*75 - 1) * 4;
LINFO(curlun, "file too big: %s\n", filename);
LINFO(curlun, "using only first %d blocks\n",
(int) num_sectors);
}
}
if (num_sectors < min_sectors) {
LINFO(curlun, "file too small: %s\n", filename);
rc = -ETOOSMALL;
goto out;
Expand Down Expand Up @@ -3845,9 +3972,12 @@ static int __init fsg_bind(struct usb_gadget *gadget)
goto out;

if (mod_data.removable) { // Enable the store_xxx attributes
dev_attr_ro.attr.mode = dev_attr_file.attr.mode = 0644;
dev_attr_ro.store = store_ro;
dev_attr_file.attr.mode = 0644;
dev_attr_file.store = store_file;
if (!mod_data.cdrom) {
dev_attr_ro.attr.mode = 0644;
dev_attr_ro.store = store_ro;
}
}

/* Find out how many LUNs there should be */
Expand All @@ -3872,6 +4002,8 @@ static int __init fsg_bind(struct usb_gadget *gadget)
for (i = 0; i < fsg->nluns; ++i) {
curlun = &fsg->luns[i];
curlun->ro = mod_data.ro[i];
if (mod_data.cdrom)
curlun->ro = 1;
curlun->dev.release = lun_release;
curlun->dev.parent = &gadget->dev;
curlun->dev.driver = &fsg_driver.driver;
Expand Down Expand Up @@ -4031,9 +4163,9 @@ static int __init fsg_bind(struct usb_gadget *gadget)
mod_data.protocol_name, mod_data.protocol_type);
DBG(fsg, "VendorID=x%04x, ProductID=x%04x, Release=x%04x\n",
mod_data.vendor, mod_data.product, mod_data.release);
DBG(fsg, "removable=%d, stall=%d, buflen=%u\n",
DBG(fsg, "removable=%d, stall=%d, cdrom=%d, buflen=%u\n",
mod_data.removable, mod_data.can_stall,
mod_data.buflen);
mod_data.cdrom, mod_data.buflen);
DBG(fsg, "I/O thread pid: %d\n", task_pid_nr(fsg->thread_task));

set_bit(REGISTERED, &fsg->atomic_bitflags);
Expand Down

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