On Tuesday 23 November 2010 07:18 pm, Weongyo Jeong wrote: > On Tue, Nov 23, 2010 at 06:52:36PM -0500, Jung-uk Kim wrote: > > On Tuesday 23 November 2010 06:31 pm, Jung-uk Kim wrote: > > > [CC sanitized] > > > > > > On Tuesday 23 November 2010 06:01 pm, Hans Petter Selasky wrote: > > > > Dear Weongyo, > > > > > > > > > NACK. You already could recognize that the patch is quite > > > > > big and multiple patches are mixed into one. Please > > > > > separate into smallest pieces then send freebsd-usb@ again. > > > > > I don't want to do a jumbo jump. > > > > Technically, I don't like the copy-and-pasted code from bpf.c and > > bpf_filter.c. Was it really necessary? Is the dump file in PCAP > > format? > > > > Please enlighten me if I missed something. > > The following paragraph is extracted from email I sent to rwatson@ > because he also asked same question to me. And I added CC to > freebsd-usb@ to share my story with other developers who might > think similar. > > Hello Roberts, > > I understand what you're worry and agree with you that if I could > remove this duplication it'd be best one. I think it could be > happen enough later if we could reach the consensus. > > The biggest confusions I encountered during implementing? > (porting) it for USB packet filter were as follows. Please let me > know if there are something I missed: > > - BPF was normally for ethernet frames (most operations were > based on mbuf including the machine filter and there were a lot of > assumptions the input buffer is mbuf type. For example, handling > BPF_LD|BPF_W|BPF_ABS). However the USB packet isn't like mbuf > style that it's just a linear buffer. So the most important code > or assumption wasn't compatible.
BPF can deal with linear buffer just fine. For example, ng_bpf(4) does it. Please see sys/netgraph/ng_bpf.c. > - Just making the patch for BPF code, it looked like a trick or > a hack to me because I couldn't define what BPF should be. If you don't want to touch bpf.c for some reason, netgraph(4) (-> ng_bpf) may be an alternate solution for you. > - I could not define BPF exactly myself that what BPF should > cover. I agreed with that BPF is for ethernet packet filtering but > could not make sure myself that BPF could cover USB packets. BPF is a generic packet filter machine, i.e., bytecode is generic enough for any type of data stream. Jung-uk Kim _______________________________________________ freebsd-usb@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-usb To unsubscribe, send any mail to "freebsd-usb-unsubscr...@freebsd.org"
