As discussed in length on the mailinglist, USBDEVFS_URB_BULK_CONTINUATION
does not work as it should when combined with USBDEVFS_URB_SHORT_NOT_OK
(which is its intended use) on devices attached to an XHCI controller.
Note that this patch only does not advertise the cap, bulk transfers
with USBDEVFS_URB_BULK_CONTINUATION will still be accepted. Returning
-EINVAL for them would break existing apps, and in most cases the
troublesome scenario wrt USBDEVFS_URB_SHORT_NOT_OK urbs on XHCI controllers
will never get hit, so this would break working use cases.
The disadvantage of not returning -EINVAL is that cases were it is causing
real trouble may go undetected / the cause of the trouble may be unclear,
but this is the best we can do.
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
---
drivers/usb/core/devio.c | 3 ++-
drivers/usb/host/xhci.c | 2 ++
include/linux/usb.h | 5 +++++
3 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index de5631e..f597c0e 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -1823,7 +1823,8 @@ static int proc_get_capabilities(struct dev_state *ps, void __user *arg)
__u32 caps = 0;
caps |= USBDEVFS_CAP_ZERO_PACKET | USBDEVFS_CAP_NO_PACKET_SIZE_LIM;
- caps |= USBDEVFS_CAP_BULK_CONTINUATION;
+ if (!ps->dev->bus->no_stop_on_short_tx)
+ caps |= USBDEVFS_CAP_BULK_CONTINUATION;
if (put_user(caps, (__u32 __user *)arg))
return -EFAULT;
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 36641a7..67834ae 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -3974,6 +3974,8 @@ int xhci_gen_setup(struct usb_hcd *hcd, xhci_get_quirks_t get_quirks)
/* Accept arbitrarily long scatter-gather lists */
hcd->self.sg_tablesize = ~0;
+ /* XHCI controllers don't stop the ep queue on short tx :| */
+ hcd->self.no_stop_on_short_tx = 1;
if (usb_hcd_is_primary_hcd(hcd)) {
xhci = kzalloc(sizeof(struct xhci_hcd), GFP_KERNEL);
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 73b68d1..b9069a5 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -331,6 +331,11 @@ struct usb_bus {
u8 otg_port; /* 0, or number of OTG/HNP port */
unsigned is_b_host:1; /* true during some HNP roleswitches */
unsigned b_hnp_enable:1; /* OTG: did A-Host enable HNP? */
+ unsigned no_stop_on_short_tx:1; /*
+ * Quirk: some controllers don't stop
+ * the ep queue on a short transfer
+ * with the URB_SHORT_NOT_OK flag set.
+ */
unsigned sg_tablesize; /* 0 or largest number of sg list entries */
int devnum_next; /* Next open device number in
--
1.7.10.4
--
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