Re: [Qemu-devel] CAN device

[Yang Jin]

Hi,
Thanks, Andreas. It really help me a lot.

When I man qemu, I found "path specifies the name of the serial device to open". Does that mean I should have a real serial device or I cannot test it? Can I test it just in a virtual environment? When I try to open a /dev/ttyS0 through "cat /dev/ttyS0", error "Input/output error". I google it, and found many reasons can cause that error. How should I test it?

Thanks,

Jin Yang.

 

2013/6/28 Andreas Färber <address@hidden>

Hi,

Am 28.06.2013 14:19, schrieb Yang Jin:

> I try to develop a CAN device on QEMU. And I found pci-serial is similar
> to CAN.
>
> Untill now, I have some questions about how to use pci-serial on QEMU.
> Actually, QEMU use isa-serial as a default serial device. So I try to
> use isa-serial firstly.
>
> Some useful information we can get from docs/qdev-device-use.txt. I know
> that we should use "-chardev" argument to create a host part, and then
> use "-device isa-serial,iobase=IOADDR,irq=IRQ,index=IDX" to start a
> isa-serial. I get those arguments from the source file, the following
> can work.
>    "-device isa-serial,chardev=isa0,iobase=0x3f8,irq=4,index=0"
> However, when I try to create a host through "-chardev
> serial,id=isa0,path=./", error "chardev: opening backend "serial"
> failed" occurs. When change it to "-chardev
> serial,id=isa0,path=/dev/ttyS0", it works. Now, I donot know what "path"
> means? Does it have some relation to the host device? Or it's just a
> symbol means nothing.

Searching man qemu for "chardev serial" should answer that question. :)
There you will also find alternative chardev backends you can use.

> And some questions about pci bus. On docs/qdev-device-use.txt, we get
> Example: device i440FX-pcihost is on the root bus, and provides a PCI
> bus named pci.0.  To put a FOO device into its slot 4, use -device
> FOO,bus=/i440FX-pcihost/pci.0,addr=4.  The abbreviated form bus=pci.0
> also works as long as the bus name is unique.
> So, how can we get the name of the root device which we use now?

You can browse the QOM hierarchy using the ./QMP/qom-list script and an
appropriate -qmp option (e.g. unix:./qmp-sock,server,nowait).

But leaving out the bus= option should work fine just as well.

Regards,
Andreas

> I searched that for some days, but doesnot get some usefull information.
>
> Thanks,
> Jin yang.

--
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg