Re: [Qemu-devel] Fwd: Trying to write a new device / virtio-i2c ?

[Paolo Bonzini <pbonzini@redhat.com>]

Il 18/02/2014 13:48, Alex David ha scritto:
>
> 2014-02-17 17:11 GMT+01:00 Paolo Bonzini <pbonzini@redhat.com
> <mailto:pbonzini@redhat.com>>:
>
>     Il 17/02/2014 16:33, Alex David ha scritto:
>
>             If you need more than one bus, you need a new device
>         exposing the
>             I2C bus, besides the new sensor devices.  USB-I2C could be
>         one such
>             device.
>
>         So let me see if I understood well. USB-I2C (host QEMU device)
>         seems a
>         good idea, I could normally do : qemu-system-i386 -device
>         usb-I2c,chardev=foo -device usb-i2c,chardev=bar -chardev
>         socket,path=/tmp/test0,server,__nowait,id=foo -chardev
>         socket,path=/tmp/test1,server,__nowait,id=bar.
>
>
>     Almost. For QOM:
>
>         -device usb-i2c,id=usb-i2c-0
>         -device i2c-my-sensor,address=0x48,__bus=usb-i2c-0.0
>
>     For chardev:
>
>         -device usb-i2c,id=usb-i2c-0
>         -chardev socket,path=/tmp/test0,server,__nowait,id=chr-foo-0
>         -device
>     i2c-my-sensor,address=0x48,__bus=usb-i2c-0.0,chardev=chr-__foo-0
>
>     Repeat for the other buses, replacing -0 with -1 and -2.
>
>
>         I need a "USB-I2C guest kernel driver" that would register a bus
>         (i2c-1
>         for chardev foo, i2c-2 for chardev bar etc...), I guess ?
>
>
>     It exists already, drivers/i2c/busses/i2c-tiny-usb.c.
>
>
> I'm now trying to write this new USB-I2C device, I look through some of
> the code (dev-serial, dev-...), I used dev-serial code and removed the
> code that wanted to declare a chardev (I don't need one to create my
> bus, right ?).
>
> Now I'm wondering, how will be i2c-tiny-usb launched and declare a new
> /dev/i2c-N, with my device. I found :
>
> static struct usb_device_id i2c_tiny_usb_table [] = {
>     { USB_DEVICE(0x0403, 0xc631) },   /* FTDI */
>     { USB_DEVICE(0x1c40, 0x0534) },   /* EZPrototypes */
>     { }                               /* Terminating entry */
> };
>
> So I figured my USB-I2C should register using these numbers ?
>
> static const USBDesc desc_i2c = {
>     .id = {
>         .idVendor          = 0x0403,
>         .idProduct         = 0xc631,
>         .bcdDevice         = 0x0400,
>         .iManufacturer     = STR_MANUFACTURER,
>         .iProduct          = STR_PRODUCT_I2C,
>         .iSerialNumber     = STR_SERIALNUMBER,
>     },
>     .full = &desc_device,
>     .str  = desc_strings,
> };
>
> However, this doesn't work, after a $ qemu-system-i386
> debian_wheezy_i386_standard.qcow2 -usb -device USB-I2C,id=usb-i2c-0, the
> driver doesn't seem to be used (/sys/class/i2c-dev/i2c-0/name isn't for
> it...), even if I modprobe i2c-tiny-usb...
> The dmesg shows it doesn't go into the "probe" function.
>
> What did I miss ?

I honestly don't know, you'll have to debug it.

Paolo