Re: custom serial driver node not created

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On Wed, May 18, 2022 at 1:59 PM Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Wed, May 18, 2022 at 01:41:18PM +0200, Belisko Marek wrote:
> > Hello,
> >
> > I'm writing serial tty driver (it's SPI/UART converter) and I get
> > inspired by this driver:
> > https://github.com/raspberrypi/linux/blob/rpi-5.15.y/drivers/tty/serial/sc16is7xx.c
> >
> > I have driver probed and also added port to driver which I see in console:
> > [ 2616.826105] spi0.0: ttyTX0 at I/O 0x1 (irq = 0, base_baud = 9375)
> > is a test_driver
> >
> > so I should see it in /dev/ttyTX0 but it seems node is not created.
> > Udev is running on a platform.
> > Any ideas what can cause this?
>
> Without seeing the code itself, it's almost impossible to guess.
>
> Also note that udev does not create device nodes (hasn't for over a
> decade).  devtmpfs in the kernel does that, udev just helps with
> managing the permissions of created nodes if needed.
OK thanks for clarification.
>
> And why did you pick the ttyTX name?  That's already reserved for that
> driver, you should use a new one, right?
I've should used also others like ttyTEST but result was same.
>
> And what hardware are you writing this driver for that we don't already
> have a driver for it?
I'm writing a driver for the following model: Linux CPU is connected
with SPI with another CPU (Cortex M3) and this other CPU performs UART
handling based on data which comes over SPI. I would like to expose
Cortex M3 UARTS on linux as tty ports so it will act as standar serial
device.

Code can be found here: https://pastebin.com/6qpUw2Jt


Thanks,

marek
>
> thanks,
>
> greg k-h



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