USB: g_file_storage: don't send padding when stall=n

This patch (as1455) removes the extra padding sent by g_file_storage
and g_mass_storage when the gadget wants to send less data than
requested by the host and isn't allowed to halt the bulk-IN endpoint.

Although the Bulk-Only Transport specification requires the padding to
be present, it isn't truly needed since the transfer will be terminated
by a short packet anyway.  Furthermore, many existing devices don't
bother to send any padding.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-By: Michal Nazarewicz <mina86@mina86.com>
CC: Roger Quadros <roger.quadros@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 23 insertions, 84 deletions

diff --git a/drivers/usb/gadget/f_mass_storage.c b/drivers/usb/gadget/f_mass_storage.c
index 125587ac5d0b..98d6b39061d2 100644
--- a/drivers/usb/gadget/f_mass_storage.c
+++ b/drivers/usb/gadget/f_mass_storage.c
@@ -1569,37 +1569,6 @@ static int wedge_bulk_in_endpoint(struct fsg_dev *fsg)
         return rc;
 }
 
-static int pad_with_zeros(struct fsg_dev *fsg)
-{
-        struct fsg_buffhd       *bh = fsg->common->next_buffhd_to_fill;
-        u32                     nkeep = bh->inreq->length;
-        u32                     nsend;
-        int                     rc;
-
-        bh->state = BUF_STATE_EMPTY;            /* For the first iteration */
-        fsg->common->usb_amount_left = nkeep + fsg->common->residue;
-        while (fsg->common->usb_amount_left > 0) {
-
-                /* Wait for the next buffer to be free */
-                while (bh->state != BUF_STATE_EMPTY) {
-                        rc = sleep_thread(fsg->common);
-                        if (rc)
-                                return rc;
-                }
-
-                nsend = min(fsg->common->usb_amount_left, FSG_BUFLEN);
-                memset(bh->buf + nkeep, 0, nsend - nkeep);
-                bh->inreq->length = nsend;
-                bh->inreq->zero = 0;
-                start_transfer(fsg, fsg->bulk_in, bh->inreq,
-                               &bh->inreq_busy, &bh->state);
-                bh = fsg->common->next_buffhd_to_fill = bh->next;
-                fsg->common->usb_amount_left -= nsend;
-                nkeep = 0;
-        }
-        return 0;
-}
-
 static int throw_away_data(struct fsg_common *common)
 {
         struct fsg_buffhd       *bh;
@@ -1686,6 +1655,10 @@ static int finish_reply(struct fsg_common *common)
                 if (common->data_size == 0) {
                         /* Nothing to send */
 
+                /* Don't know what to do if common->fsg is NULL */
+                } else if (!fsg_is_set(common)) {
+                        rc = -EIO;
+
                 /* If there's no residue, simply send the last buffer */
                 } else if (common->residue == 0) {
                         bh->inreq->zero = 0;
@@ -1694,24 +1667,19 @@ static int finish_reply(struct fsg_common *common)
                         common->next_buffhd_to_fill = bh->next;
 
                 /*
-                 * For Bulk-only, if we're allowed to stall then send the
-                 * short packet and halt the bulk-in endpoint.  If we can't
-                 * stall, pad out the remaining data with 0's.
+                 * For Bulk-only, mark the end of the data with a short
+                 * packet.  If we are allowed to stall, halt the bulk-in
+                 * endpoint.  (Note: This violates the Bulk-Only Transport
+                 * specification, which requires us to pad the data if we
+                 * don't halt the endpoint.  Presumably nobody will mind.)
                  */
-                } else if (common->can_stall) {
+                } else {
                         bh->inreq->zero = 1;
                         if (!start_in_transfer(common, bh))
-                                /* Don't know what to do if
-                                 * common->fsg is NULL */
                                 rc = -EIO;
                         common->next_buffhd_to_fill = bh->next;
-                        if (common->fsg)
+                        if (common->can_stall)
                                 rc = halt_bulk_in_endpoint(common->fsg);
-                } else if (fsg_is_set(common)) {
-                        rc = pad_with_zeros(common->fsg);
-                } else {
-                        /* Don't know what to do if common->fsg is NULL */
-                        rc = -EIO;
                 }
                 break;
 
diff --git a/drivers/usb/gadget/file_storage.c b/drivers/usb/gadget/file_storage.c
index d04e0e6b019d..aebfb81f3ba4 100644
--- a/drivers/usb/gadget/file_storage.c
+++ b/drivers/usb/gadget/file_storage.c
@@ -1932,37 +1932,6 @@ static int wedge_bulk_in_endpoint(struct fsg_dev *fsg)
         return rc;
 }
 
-static int pad_with_zeros(struct fsg_dev *fsg)
-{
-        struct fsg_buffhd       *bh = fsg->next_buffhd_to_fill;
-        u32                     nkeep = bh->inreq->length;
-        u32                     nsend;
-        int                     rc;
-
-        bh->state = BUF_STATE_EMPTY;            // For the first iteration
-        fsg->usb_amount_left = nkeep + fsg->residue;
-        while (fsg->usb_amount_left > 0) {
-
-                /* Wait for the next buffer to be free */
-                while (bh->state != BUF_STATE_EMPTY) {
-                        rc = sleep_thread(fsg);
-                        if (rc)
-                                return rc;
-                }
-
-                nsend = min(fsg->usb_amount_left, (u32) mod_data.buflen);
-                memset(bh->buf + nkeep, 0, nsend - nkeep);
-                bh->inreq->length = nsend;
-                bh->inreq->zero = 0;
-                start_transfer(fsg, fsg->bulk_in, bh->inreq,
-                                &bh->inreq_busy, &bh->state);
-                bh = fsg->next_buffhd_to_fill = bh->next;
-                fsg->usb_amount_left -= nsend;
-                nkeep = 0;
-        }
-        return 0;
-}
-
 static int throw_away_data(struct fsg_dev *fsg)
 {
         struct fsg_buffhd       *bh;
@@ -2066,18 +2035,20 @@ static int finish_reply(struct fsg_dev *fsg)
                         }
                 }
 
-                /* For Bulk-only, if we're allowed to stall then send the
-                 * short packet and halt the bulk-in endpoint.  If we can't
-                 * stall, pad out the remaining data with 0's. */
+                /*
+                 * For Bulk-only, mark the end of the data with a short
+                 * packet.  If we are allowed to stall, halt the bulk-in
+                 * endpoint.  (Note: This violates the Bulk-Only Transport
+                 * specification, which requires us to pad the data if we
+                 * don't halt the endpoint.  Presumably nobody will mind.)
+                 */
                 else {
-                        if (mod_data.can_stall) {
-                                bh->inreq->zero = 1;
-                                start_transfer(fsg, fsg->bulk_in, bh->inreq,
-                                                &bh->inreq_busy, &bh->state);
-                                fsg->next_buffhd_to_fill = bh->next;
+                        bh->inreq->zero = 1;
+                        start_transfer(fsg, fsg->bulk_in, bh->inreq,
+                                        &bh->inreq_busy, &bh->state);
+                        fsg->next_buffhd_to_fill = bh->next;
+                        if (mod_data.can_stall)
                                 rc = halt_bulk_in_endpoint(fsg);
-                        } else
-                                rc = pad_with_zeros(fsg);
                 }
                 break;