> From: Sarah Sharp [mailto:sarah.a.sharp@xxxxxxxxxxxxxxx] > On Fri, Feb 25, 2011 at 01:45:03PM -0800, Paul Zimmerman wrote: > > Use the Mult and bMaxBurst values from the endpoint companion > > descriptor to calculate the max length of an isoc transfer > > > > Signed-off-by: Paul Zimmerman <paulz@xxxxxxxxxxxx> > > --- > > drivers/usb/core/urb.c | 11 ++++++++++- > > 1 files changed, 10 insertions(+), 1 deletions(-) > > > > diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c > > index c14fc08..991f33e 100644 > > --- a/drivers/usb/core/urb.c > > +++ b/drivers/usb/core/urb.c > > @@ -366,7 +366,16 @@ int usb_submit_urb(struct urb *urb, gfp_t mem_flags) > > if (xfertype == USB_ENDPOINT_XFER_ISOC) { > > int n, len; > > > > - /* FIXME SuperSpeed isoc endpoints have up to 16 bursts */ > > + /* SuperSpeed isoc endpoints have up to 16 bursts of up to > > + * 3 packets each > > + */ > > + if (dev->speed == USB_SPEED_SUPER) { > > + int burst = 1 + ep->ss_ep_comp.bMaxBurst; > > + int mult = 1 + ep->ss_ep_comp.bmAttributes; > > Paul, please don't create new variables in an if block. Create them at > the top of the function. Hi Sarah, I'm sorry, but Linus disagrees with you. He recently expressed a preference for variables that are only used within a block, to be defined within the block instead of at the top of the function. Plus I am following the style that is already used within that function. Please take a closer look. > > > + max *= burst; > > + max *= mult; > > + } > > + > > Where is max used later? max is used about 12 lines further down: len = urb->iso_frame_desc[n].length; if (len < 0 || len > max) return -EMSGSIZE; > I'll have to look further in the code to see if this actually works. I > don't think you can just use the endpoint calculations, because the > driver may want to submit a slightly shorter transfer length. It's > really the USB core's job to check whether the buffer size is bigger > than what the endpoint can handle. The code should go there instead. This code is in the USB core. Please take a closer look at the function, this is the proper place to check. I have tested this, and without the patch it is impossible to submit an isoc URB that is larger than a single packet. With the patch, it works. -- Paul -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
