On Tue, Mar 09, 2010 at 05:16:40PM +0200, Felipe Balbi wrote: > 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. That sounds like a bug we need to fix then, right? > 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. Then why not just fix u_serial.c to push the same ammount of data? > Performance is a key concept here; specially when we need to flash > hundreds of thousands of devices in a production line. Every milisecond > counts. Sure, I understand, but it seems like it is easier to fix the existing code for these minor things, than to write a whole new driver, right? If you do that, then the existing users will also benifit from those changes. thanks, greg k-h -- 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
