On Tue, Mar 09, 2010 at 06:54:30AM -0800, Greg KH wrote: > Why is this needed? Why not just use the serial driver instead? That > should provide you with exactly the same end result, right? we experienced several problems with tty layer. The biggest of them is a race between flush_to_ldisc() and ->receiv_buf() which makes the line discipline (I guess only n_tty) loose bytes in some circumstances. On top of that there's also the performance issues with tty. the u_serial.c forces us to push each bMaxPacketSize packet to the controller driver which prevents us from actually getting some good deal out of the DMA engine. With u_char.c we are unloading based on what's in the kfifo right now (maybe we should use PAGE_SIZE transfers since our kfifo is allocated using vmalloc()), and we can easily optimize that on a per-product basis. Performance is a key concept here; specially when we need to flash hundreds of thousands of devices in a production line. Every milisecond counts. I tried to explain this as much as possible on the PATCH 0/2 mail, but it seems I wasn't clear enough, sorry for that. -- balbi -- 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
