custom serial driver node not created

custom serial driver node not created

[Belisko Marek]

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?

Thanks and regards,

marek

-- 
as simple and primitive as possible
-------------------------------------------------
Marek Belisko - OPEN-NANDRA
Freelance Developer

Ruska Nova Ves 219 | Presov, 08005 Slovak Republic
Tel: +421 915 052 184
skype: marekwhite
twitter: #opennandra
web: http://open-nandra.com

Re: custom serial driver node not created

[Greg KH]

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.

And why did you pick the ttyTX name?  That's already reserved for that
driver, you should use a new one, right?

And what hardware are you writing this driver for that we don't already
have a driver for it?

thanks,

greg k-h

Re: custom serial driver node not created

[Belisko Marek]

On Wed, May 18, 2022 at 1:59 PM Greg KH <gregkh@linuxfoundation.org> 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

Re: custom serial driver node not created

[Greg KH]

On Wed, May 18, 2022 at 02:24:43PM +0200, Belisko Marek wrote:
> On Wed, May 18, 2022 at 1:59 PM Greg KH <gregkh@linuxfoundation.org> 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

Are you sure that your test_probe() call is really being called?

Re: custom serial driver node not created

[Belisko Marek]

On Wed, May 18, 2022 at 2:42 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Wed, May 18, 2022 at 02:24:43PM +0200, Belisko Marek wrote:
> > On Wed, May 18, 2022 at 1:59 PM Greg KH <gregkh@linuxfoundation.org> 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
>
> Are you sure that your test_probe() call is really being called?
Of course I've added tons of debugging to the driver and it is probed.
As I mentioned in first topic I see this printout:
[ 2616.826105] spi0.0: ttyTX0 at I/O 0x1 (irq = 0, base_baud = 9375)
is a test_driver

which came from uart_report_port() foom serial_core.c
>

marek
-- 
as simple and primitive as possible
-------------------------------------------------
Marek Belisko - OPEN-NANDRA
Freelance Developer

Ruska Nova Ves 219 | Presov, 08005 Slovak Republic
Tel: +421 915 052 184
skype: marekwhite
twitter: #opennandra
web: http://open-nandra.com