Alan Stern wrote: > 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. > Certainly not anymore. The previous iteration of this code used this function. Thanks for catching that. >> 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. If this is what you prefer, I have no problem with it. I'll post a v2 of the series after some testing. Jason. -- 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
