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Re: [Qemu-devel] [PATCH V4 2/7] CAN bus support to connect bust to Linux
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH V4 2/7] CAN bus support to connect bust to Linux host SocketCAN interface. |
Date: |
Mon, 22 Jan 2018 10:28:51 +0000 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
On Fri, Jan 19, 2018 at 10:37:22AM -0300, Philippe Mathieu-Daudé wrote:
> On 01/19/2018 05:51 AM, Pavel Pisa wrote:
> > On Tuesday 16 of January 2018 01:12:09 Philippe Mathieu-Daudé wrote:
> >> On 01/15/2018 06:29 PM, Pavel Pisa wrote:
> > But if the second format is preferred then I update the patch.
> >
> >>> Trace events seems as nice feature. But simple text printf
> >>> like output has been enough till now for CAN testing.
> >>> There is no debugging output in production build.
> >>> So I would add tracing infrastructure later if needed.
> >>
> >> They are as useful as console printf, but less invasive and more
> >> powerful: you can use a much precise timing, select which set of events
> >> to display without having to recompile.
> >> The default backend behaves as console printf.
> >>
> >> You should try them :)
> >
> > I have tried them on
> >
> > pci_update_mappings_del
> > pci_update_mappings_add
> > pci_cfg_write
> >
> > and they work great. They would be nice for SJA1000
> > register accesses, PCI boards configuration etc.
> > I am not sure how to use them for CAN messages
> > which has a variable length data field.
>
> Yes, I hit this problem with variable length data in the SD Bus.
>
> Let's ask Stefan what is the best approach (he said "Tracing is not
> great for dumping large amounts of data")
Yes, tracing isn't pcap. It's not designed for dumping payloads -
especially when the length is more than 64 bytes or so.
I suggest writing out a pcap file so wireshark or tcpdump can be used to
analyze it. The code is pretty simple, see net/dump.c.
Stefan
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- [Qemu-devel] [PATCH V4 1/7] CAN bus simple messages transport implementation for QEMU, (continued)
Re: [Qemu-devel] [PATCH V4 2/7] CAN bus support to connect bust to Linux host SocketCAN interface., Philippe Mathieu-Daudé, 2018/01/19
[Qemu-devel] [PATCH V4 3/7] CAN bus SJA1000 chip register level emulation for QEMU, pisa, 2018/01/14
[Qemu-devel] [PATCH V4 4/7] CAN bus Kvaser PCI CAN-S (single SJA1000 channel) emulation added., pisa, 2018/01/14
[Qemu-devel] [PATCH V4 5/7] QEMU CAN bus emulation documentation, pisa, 2018/01/14
[Qemu-devel] [PATCH V4 6/7] CAN bus PCM-3680I PCI (dual SJA1000 channel) emulation added., pisa, 2018/01/14