[Qemu-devel] CAN device

[Qemu-devel] CAN device

[Yang Jin]

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Hi,
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.

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?

I searched that for some days, but doesnot get some usefull information.

Thanks,
Jin yang.

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Re: [Qemu-devel] CAN device

[Andreas Färber]

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

Re: [Qemu-devel] CAN device

[Yang Jin]

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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 <afaerber@suse.de>

> 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
>

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Re: [Qemu-devel] CAN device

[Andreas Färber]

Hi,

Am 30.06.2013 14:25, schrieb Yang Jin:
> 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".

-chardev serial is for a serial device. If you cannot or don't want to
use one, just use a different -chardev parameter. The man page I pointed
you to documents quite a few: null, file, pipe, stdio and many more. I
cannot guess which one is best for what you are trying to do. ;)

Regards,
Andreas

P.S. Please avoid top-posting on the mailing list.

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