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Subject2.6.13 ub 4: Zaitcev's quasi-S/G
Back out Axboe-style quasi-S/G and replace it with one command and
repeated URBs. This is similar to what usb-storage does, only instead
of a few URBs allocated together, one URB is reused.

Jens's idea was very nice, but it collapsed when I had to support
packet commads for CD burning. I cannot issue two or more packet
commands where application expected only one.

However, burning does not work completely yet. The cdrecord starts,
recognizes the device, then aborts without writing a TOC.

Signed-off-by: Pete Zaitcev <zaitcev@yahoo.com>

--- linux-2.6.13-rc6-gregkh/drivers/block/ub.c 2005-08-14 21:02:39.000000000 -0700
+++ linux-2.6.13-rc4-lem/drivers/block/ub.c 2005-08-14 20:45:52.000000000 -0700
@@ -235,27 +235,16 @@ struct ub_scsi_cmd {

int stat_count; /* Retries getting status. */

- /*
- * We do not support transfers from highmem pages
- * because the underlying USB framework does not do what we need.
- */
- char *data; /* Requested buffer */
unsigned int len; /* Requested length */
+ unsigned int current_sg;
+ unsigned int nsg; /* sgv[nsg] */
+ struct scatterlist sgv[UB_MAX_REQ_SG];

struct ub_lun *lun;
void (*done)(struct ub_dev *, struct ub_scsi_cmd *);
void *back;
};

-struct ub_request {
- struct request *rq;
- unsigned char dir;
- unsigned int current_block;
- unsigned int current_sg;
- unsigned int nsg; /* sgv[nsg] */
- struct scatterlist sgv[UB_MAX_REQ_SG];
-};
-
/*
*/
struct ub_capacity {
@@ -351,8 +340,6 @@ struct ub_lun {
int readonly;
int first_open; /* Kludge. See ub_bd_open. */

- struct ub_request urq;
-
/* Use Ingo's mempool if or when we have more than one command. */
/*
* Currently we never need more than one command for the whole device.
@@ -410,19 +397,16 @@ static void ub_cleanup(struct ub_dev *sc
static int ub_request_fn_1(struct ub_lun *lun, struct request *rq);
static int ub_cmd_build_block(struct ub_dev *sc, struct ub_lun *lun,
struct ub_scsi_cmd *cmd, struct request *rq);
-static void ub_scsi_build_block(struct ub_lun *lun,
- struct ub_scsi_cmd *cmd, struct ub_request *urq);
static int ub_cmd_build_packet(struct ub_dev *sc, struct ub_lun *lun,
struct ub_scsi_cmd *cmd, struct request *rq);
static void ub_rw_cmd_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
static void ub_end_rq(struct request *rq, int uptodate);
-static int ub_request_advance(struct ub_dev *sc, struct ub_lun *lun,
- struct ub_request *urq, struct ub_scsi_cmd *cmd);
static int ub_submit_scsi(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
static void ub_urb_complete(struct urb *urb, struct pt_regs *pt);
static void ub_scsi_action(unsigned long _dev);
static void ub_scsi_dispatch(struct ub_dev *sc);
static void ub_scsi_urb_compl(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
+static void ub_data_start(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
static void ub_state_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd, int rc);
static int __ub_state_stat(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
static void ub_state_stat(struct ub_dev *sc, struct ub_scsi_cmd *cmd);
@@ -793,8 +777,6 @@ static int ub_request_fn_1(struct ub_lun
return 0;
}

- if (lun->urq.rq != NULL)
- return -1;
if ((cmd = ub_get_cmd(lun)) == NULL)
return -1;
memset(cmd, 0, sizeof(struct ub_scsi_cmd));
@@ -813,7 +795,7 @@ static int ub_request_fn_1(struct ub_lun
cmd->state = UB_CMDST_INIT;
cmd->lun = lun;
cmd->done = ub_rw_cmd_done;
- cmd->back = &lun->urq;
+ cmd->back = rq;

cmd->tag = sc->tagcnt++;
if (ub_submit_scsi(sc, cmd) != 0) {
@@ -828,22 +810,20 @@ static int ub_request_fn_1(struct ub_lun
static int ub_cmd_build_block(struct ub_dev *sc, struct ub_lun *lun,
struct ub_scsi_cmd *cmd, struct request *rq)
{
- struct ub_request *urq;
int ub_dir;
int n_elem;
-
- urq = &lun->urq;
- memset(urq, 0, sizeof(struct ub_request));
+ unsigned int block, nblks;

if (rq_data_dir(rq) == WRITE)
ub_dir = UB_DIR_WRITE;
else
ub_dir = UB_DIR_READ;
+ cmd->dir = ub_dir;

/*
* get scatterlist from block layer
*/
- n_elem = blk_rq_map_sg(lun->disk->queue, rq, &urq->sgv[0]);
+ n_elem = blk_rq_map_sg(lun->disk->queue, rq, &cmd->sgv[0]);
if (n_elem <= 0) {
printk(KERN_INFO "%s: failed request map (%d)\n",
sc->name, n_elem); /* P3 */
@@ -854,7 +834,7 @@ static int ub_cmd_build_block(struct ub_
sc->name, n_elem);
return -1;
}
- urq->nsg = n_elem;
+ cmd->nsg = n_elem;
sc->sg_stat[n_elem]++;

/*
@@ -863,29 +843,10 @@ static int ub_cmd_build_block(struct ub_
* The call to blk_queue_hardsect_size() guarantees that request
* is aligned, but it is given in terms of 512 byte units, always.
*/
- urq->current_block = rq->sector >> lun->capacity.bshift;
- // nblks = rq->nr_sectors >> lun->capacity.bshift;
-
- urq->rq = rq;
- urq->current_sg = 0;
- urq->dir = ub_dir;
+ block = rq->sector >> lun->capacity.bshift;
+ nblks = rq->nr_sectors >> lun->capacity.bshift;

- ub_scsi_build_block(lun, cmd, urq);
- return 0;
-}
-
-static void ub_scsi_build_block(struct ub_lun *lun,
- struct ub_scsi_cmd *cmd, struct ub_request *urq)
-{
- struct scatterlist *sg;
- unsigned int block, nblks;
-
- sg = &urq->sgv[urq->current_sg];
-
- block = urq->current_block;
- nblks = sg->length >> (lun->capacity.bshift + 9);
-
- cmd->cdb[0] = (urq->dir == UB_DIR_READ)? READ_10: WRITE_10;
+ cmd->cdb[0] = (ub_dir == UB_DIR_READ)? READ_10: WRITE_10;
/* 10-byte uses 4 bytes of LBA: 2147483648KB, 2097152MB, 2048GB */
cmd->cdb[2] = block >> 24;
cmd->cdb[3] = block >> 16;
@@ -895,34 +856,15 @@ static void ub_scsi_build_block(struct u
cmd->cdb[8] = nblks;
cmd->cdb_len = 10;

- cmd->dir = urq->dir;
- cmd->data = page_address(sg->page) + sg->offset;
- cmd->len = sg->length;
+ cmd->len = rq->nr_sectors * 512;
+
+ return 0;
}

static int ub_cmd_build_packet(struct ub_dev *sc, struct ub_lun *lun,
struct ub_scsi_cmd *cmd, struct request *rq)
{
- struct ub_request *urq;
-
- urq = &lun->urq;
- memset(urq, 0, sizeof(struct ub_request));
- urq->rq = rq;
- sc->sg_stat[0]++;
-
- if (rq->data_len != 0 && rq->data == NULL) {
- static int do_print = 1;
- if (do_print) {
- printk(KERN_WARNING "%s: unmapped packet request"
- " flags 0x%lx length %d\n",
- sc->name, rq->flags, rq->data_len);
- do_print = 0;
- }
- return -1;
- }
-
- memcpy(&cmd->cdb, rq->cmd, rq->cmd_len);
- cmd->cdb_len = rq->cmd_len;
+ int n_elem;

if (rq->data_len == 0) {
cmd->dir = UB_DIR_NONE;
@@ -931,8 +873,29 @@ static int ub_cmd_build_packet(struct ub
cmd->dir = UB_DIR_WRITE;
else
cmd->dir = UB_DIR_READ;
+
}
- cmd->data = rq->data;
+
+ /*
+ * get scatterlist from block layer
+ */
+ n_elem = blk_rq_map_sg(lun->disk->queue, rq, &cmd->sgv[0]);
+ if (n_elem < 0) {
+ printk(KERN_INFO "%s: failed request map (%d)\n",
+ sc->name, n_elem); /* P3 */
+ return -1;
+ }
+ if (n_elem > UB_MAX_REQ_SG) { /* Paranoia */
+ printk(KERN_WARNING "%s: request with %d segments\n",
+ sc->name, n_elem);
+ return -1;
+ }
+ cmd->nsg = n_elem;
+ sc->sg_stat[n_elem]++;
+
+ memcpy(&cmd->cdb, rq->cmd, rq->cmd_len);
+ cmd->cdb_len = rq->cmd_len;
+
cmd->len = rq->data_len;

return 0;
@@ -940,33 +903,32 @@ static int ub_cmd_build_packet(struct ub

static void ub_rw_cmd_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
+ struct request *rq = cmd->back;
struct ub_lun *lun = cmd->lun;
- struct ub_request *urq = cmd->back;
- struct request *rq;
int uptodate;

- rq = urq->rq;
-
- if (blk_pc_request(rq)) {
- /* UB_SENSE_SIZE is smaller than SCSI_SENSE_BUFFERSIZE */
- memcpy(rq->sense, sc->top_sense, UB_SENSE_SIZE);
- rq->sense_len = UB_SENSE_SIZE;
- }
-
- if (cmd->error == 0)
+ if (cmd->error == 0) {
uptodate = 1;
- else
- uptodate = 0;

- if (cmd->error == 0 && urq->current_sg+1 < urq->nsg) {
- if (ub_request_advance(sc, lun, urq, cmd) == 0) {
- /* Stay on target... */
- return;
+ if (blk_pc_request(rq)) {
+ if (cmd->act_len >= rq->data_len)
+ rq->data_len = 0;
+ else
+ rq->data_len -= cmd->act_len;
}
+ } else {
uptodate = 0;
- }

- urq->rq = NULL;
+ if (blk_pc_request(rq)) {
+ /* UB_SENSE_SIZE is smaller than SCSI_SENSE_BUFFERSIZE */
+ memcpy(rq->sense, sc->top_sense, UB_SENSE_SIZE);
+ rq->sense_len = UB_SENSE_SIZE;
+ if (sc->top_sense[0] != 0)
+ rq->errors = SAM_STAT_CHECK_CONDITION;
+ else
+ rq->errors = DID_ERROR << 16;
+ }
+ }

ub_put_cmd(lun, cmd);
ub_end_rq(rq, uptodate);
@@ -982,40 +944,6 @@ static void ub_end_rq(struct request *rq
end_that_request_last(rq);
}

-static int ub_request_advance(struct ub_dev *sc, struct ub_lun *lun,
- struct ub_request *urq, struct ub_scsi_cmd *cmd)
-{
- struct scatterlist *sg;
- unsigned int nblks;
-
- /* XXX This is temporary, until we sort out S/G in packet requests. */
- if (blk_pc_request(urq->rq)) {
- printk(KERN_WARNING
- "2-segment packet request completed\n"); /* P3 */
- return -1;
- }
-
- sg = &urq->sgv[urq->current_sg];
- nblks = sg->length >> (lun->capacity.bshift + 9);
- urq->current_block += nblks;
- urq->current_sg++;
- sg++;
-
- memset(cmd, 0, sizeof(struct ub_scsi_cmd));
- ub_scsi_build_block(lun, cmd, urq);
- cmd->state = UB_CMDST_INIT;
- cmd->lun = lun;
- cmd->done = ub_rw_cmd_done;
- cmd->back = &lun->urq;
-
- cmd->tag = sc->tagcnt++;
- if (ub_submit_scsi(sc, cmd) != 0) {
- return -1;
- }
-
- return 0;
-}
-
/*
* Submit a regular SCSI operation (not an auto-sense).
*
@@ -1171,7 +1099,6 @@ static void ub_scsi_urb_compl(struct ub_
{
struct urb *urb = &sc->work_urb;
struct bulk_cs_wrap *bcs;
- int pipe;
int rc;

if (atomic_read(&sc->poison)) {
@@ -1272,38 +1199,13 @@ static void ub_scsi_urb_compl(struct ub_
goto Bad_End;
}

- if (cmd->dir == UB_DIR_NONE) {
+ if (cmd->dir == UB_DIR_NONE || cmd->nsg < 1) {
ub_state_stat(sc, cmd);
return;
}

- UB_INIT_COMPLETION(sc->work_done);
-
- if (cmd->dir == UB_DIR_READ)
- pipe = sc->recv_bulk_pipe;
- else
- pipe = sc->send_bulk_pipe;
- sc->last_pipe = pipe;
- usb_fill_bulk_urb(&sc->work_urb, sc->dev, pipe,
- cmd->data, cmd->len, ub_urb_complete, sc);
- sc->work_urb.transfer_flags = URB_ASYNC_UNLINK;
- sc->work_urb.actual_length = 0;
- sc->work_urb.error_count = 0;
- sc->work_urb.status = 0;
-
- if ((rc = usb_submit_urb(&sc->work_urb, GFP_ATOMIC)) != 0) {
- /* XXX Clear stalls */
- printk("ub: data #%d submit failed (%d)\n", cmd->tag, rc); /* P3 */
- ub_complete(&sc->work_done);
- ub_state_done(sc, cmd, rc);
- return;
- }
-
- sc->work_timer.expires = jiffies + UB_DATA_TIMEOUT;
- add_timer(&sc->work_timer);
-
- cmd->state = UB_CMDST_DATA;
- ub_cmdtr_state(sc, cmd);
+ // udelay(125); // usb-storage has this
+ ub_data_start(sc, cmd);

} else if (cmd->state == UB_CMDST_DATA) {
if (urb->status == -EPIPE) {
@@ -1325,16 +1227,22 @@ static void ub_scsi_urb_compl(struct ub_
if (urb->status == -EOVERFLOW) {
/*
* A babble? Failure, but we must transfer CSW now.
+ * XXX This is going to end in perpetual babble. Reset.
*/
cmd->error = -EOVERFLOW; /* A cheap trick... */
- } else {
- if (urb->status != 0)
- goto Bad_End;
+ ub_state_stat(sc, cmd);
+ return;
}
+ if (urb->status != 0)
+ goto Bad_End;

- cmd->act_len = urb->actual_length;
+ cmd->act_len += urb->actual_length;
ub_cmdtr_act_len(sc, cmd);

+ if (++cmd->current_sg < cmd->nsg) {
+ ub_data_start(sc, cmd);
+ return;
+ }
ub_state_stat(sc, cmd);

} else if (cmd->state == UB_CMDST_STAT) {
@@ -1469,6 +1377,46 @@ Bad_End: /* Little Excel is dead */

/*
* Factorization helper for the command state machine:
+ * Initiate a data segment transfer.
+ */
+static void ub_data_start(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
+{
+ struct scatterlist *sg = &cmd->sgv[cmd->current_sg];
+ int pipe;
+ int rc;
+
+ UB_INIT_COMPLETION(sc->work_done);
+
+ if (cmd->dir == UB_DIR_READ)
+ pipe = sc->recv_bulk_pipe;
+ else
+ pipe = sc->send_bulk_pipe;
+ sc->last_pipe = pipe;
+ usb_fill_bulk_urb(&sc->work_urb, sc->dev, pipe,
+ page_address(sg->page) + sg->offset, sg->length,
+ ub_urb_complete, sc);
+ sc->work_urb.transfer_flags = URB_ASYNC_UNLINK;
+ sc->work_urb.actual_length = 0;
+ sc->work_urb.error_count = 0;
+ sc->work_urb.status = 0;
+
+ if ((rc = usb_submit_urb(&sc->work_urb, GFP_ATOMIC)) != 0) {
+ /* XXX Clear stalls */
+ printk("ub: data #%d submit failed (%d)\n", cmd->tag, rc); /* P3 */
+ ub_complete(&sc->work_done);
+ ub_state_done(sc, cmd, rc);
+ return;
+ }
+
+ sc->work_timer.expires = jiffies + UB_DATA_TIMEOUT;
+ add_timer(&sc->work_timer);
+
+ cmd->state = UB_CMDST_DATA;
+ ub_cmdtr_state(sc, cmd);
+}
+
+/*
+ * Factorization helper for the command state machine:
* Finish the command.
*/
static void ub_state_done(struct ub_dev *sc, struct ub_scsi_cmd *cmd, int rc)
@@ -1552,6 +1500,7 @@ static void ub_state_stat_counted(struct
static void ub_state_sense(struct ub_dev *sc, struct ub_scsi_cmd *cmd)
{
struct ub_scsi_cmd *scmd;
+ struct scatterlist *sg;
int rc;

if (cmd->cdb[0] == REQUEST_SENSE) {
@@ -1560,12 +1509,17 @@ static void ub_state_sense(struct ub_dev
}

scmd = &sc->top_rqs_cmd;
+ memset(scmd, 0, sizeof(struct ub_scsi_cmd));
scmd->cdb[0] = REQUEST_SENSE;
scmd->cdb[4] = UB_SENSE_SIZE;
scmd->cdb_len = 6;
scmd->dir = UB_DIR_READ;
scmd->state = UB_CMDST_INIT;
- scmd->data = sc->top_sense;
+ scmd->nsg = 1;
+ sg = &scmd->sgv[0];
+ sg->page = virt_to_page(sc->top_sense);
+ sg->offset = (unsigned int)sc->top_sense & (PAGE_SIZE-1);
+ sg->length = UB_SENSE_SIZE;
scmd->len = UB_SENSE_SIZE;
scmd->lun = cmd->lun;
scmd->done = ub_top_sense_done;
@@ -1628,7 +1582,7 @@ static int ub_submit_clear_stall(struct
*/
static void ub_top_sense_done(struct ub_dev *sc, struct ub_scsi_cmd *scmd)
{
- unsigned char *sense = scmd->data;
+ unsigned char *sense = sc->top_sense;
struct ub_scsi_cmd *cmd;

/*
@@ -1920,6 +1874,7 @@ static int ub_sync_read_cap(struct ub_de
struct ub_capacity *ret)
{
struct ub_scsi_cmd *cmd;
+ struct scatterlist *sg;
char *p;
enum { ALLOC_SIZE = sizeof(struct ub_scsi_cmd) + 8 };
unsigned long flags;
@@ -1940,7 +1895,11 @@ static int ub_sync_read_cap(struct ub_de
cmd->cdb_len = 10;
cmd->dir = UB_DIR_READ;
cmd->state = UB_CMDST_INIT;
- cmd->data = p;
+ cmd->nsg = 1;
+ sg = &cmd->sgv[0];
+ sg->page = virt_to_page(p);
+ sg->offset = (unsigned int)p & (PAGE_SIZE-1);
+ sg->length = 8;
cmd->len = 8;
cmd->lun = lun;
cmd->done = ub_probe_done;
-
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