On Mon, Jan 7, 2019 at 10:05 AM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Mon, Jan 07, 2019 at 09:57:56AM +0100, Gerhard Khüny wrote:
> > Hello,
> >
> > I have a question regarding the function
> > serial_pci_is_class_communication() in 8250_pci:
> >
> > static int serial_pci_is_class_communication(struct pci_dev *dev) {
> >
> > /*
> > * If it is not a communications device or the programming
> > * interface is greater than 6, give up.
> > */
> > if ((((dev->class >> 8) != PCI_CLASS_COMMUNICATION_SERIAL) &&
> > ((dev->class >> 8) != PCI_CLASS_COMMUNICATION_MULTISERIAL) &&
> > ((dev->class >> 8) != PCI_CLASS_COMMUNICATION_MODEM)) ||
> > (dev->class & 0xff) > 6)
> > return -ENODEV;
> >
> > return 0;
> >
> > }
> >
> > We have implemented a serial interface in a FPGA. The existing driver
> > 8250_pci is working perfect for us. Only the check using the function
> > serial_pci_is_class_communication does not work since the PCI class is
> > 0x05, subclass is 0x00 and programming interface is 0x00 for our
> > device.
>
> Then fix your PCI device identifier structure :)
>
The problem is that the FPGA holds additional functionality (e.g. .
RTC, Hex-switch,..). The device therefore is not a real serial device
but it has implemented a serial interface.
> > My question is, if it is the intention to exclude PCI class memory
> > devices implementing a serial driver? The comment in the code could
> > say something different.
>
> If your device says it is a memory device and not a serial device, how
> could the kernel "know" it is really a serial device?
>
Because the init function returns no error.
Why not allow memory devices also?
> Please read the PCI spec for what a class device really means, and if
> your device does follow the serial specification, then change your pci
> device structure of your device to properly tell the host operating
> system that it is a serial device.
>
> thanks,
>
> greg k-h
