On Tue, 9 Mar 2010, Jason Wessel wrote: > This patch tries to solve the problem that data is lost because there > are too many outstanding transmit urb's while trying to execute > printk's to a console. The same is true if you try something like > "echo t > /proc/sysrq-trigger". > > This patch takes the route of forcibly polling the hcd device to drain > the urb queue in order to initiate the bulk write call backs. This > only happens if the device is a usb serial console device that sets > the max_in_flight_urbs to a non zero value in the serial device > structure. > > A few millisecond penalty will get incurred to allow the hcd controller > to complete a write urb, else the console data is thrown away. > > The max_in_flight_urbs was reduced in the usb_debug driver because it > is highly desired to push things out to the console in a timely > fashion and there is no need to have a queue that large for the > interrupt driven mode of operation when used through the tty > interface. > --- a/drivers/usb/core/hcd.c > +++ b/drivers/usb/core/hcd.c > @@ -1973,6 +1973,7 @@ irqreturn_t usb_hcd_irq (int irq, void *__hcd) > local_irq_restore(flags); > return rc; > } > +EXPORT_SYMBOL_GPL(usb_hcd_irq); Is there any reason for EXPORTing this? It doesn't get used anywhere else. > index a3cdb09..703f407 100644 > --- a/drivers/usb/core/hcd.h > +++ b/drivers/usb/core/hcd.h > @@ -318,6 +318,7 @@ extern void usb_put_hcd(struct usb_hcd *hcd); > extern int usb_add_hcd(struct usb_hcd *hcd, > unsigned int irqnum, unsigned long irqflags); > extern void usb_remove_hcd(struct usb_hcd *hcd); > +extern void usb_hcd_poll_irq(struct usb_device *udev); > > struct platform_device; > extern void usb_hcd_platform_shutdown(struct platform_device *dev); It might be better to put this in a "public" header file; that is, something under include/linux/usb or include/linux/usb.h. You could even take the "_hcd" part out of the name, because the interface uses only a struct usb_device, not a struct usb_hcd. Alan Stern -- 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
