No controller seen in /sys/kernel/config/pci_ep/controllers

No controller seen in /sys/kernel/config/pci_ep/controllers

[Ajay Garg]

Hello everyone.

The kernel has been built with :

###################################
CONFIG_PCI_ENDPOINT=y
CONFIG_PCI_ENDPOINT_CONFIGFS=y
CONFIG_PCI_EPF_TEST=y
CONFIG_PCI_ENDPOINT_TEST=y
###################################


Thereafter, following are seen :

###################################
$ sudo mount none /sys/kernel/config/ -t configfs
mount: /sys/kernel/config: none already mounted or mount point busy.

$ ls -lrth /sys/class/pci_epc/
total 0

$ ls -lrth /sys/kernel/config
total 0
drwxr-xr-x 4 root root 0 Jul 13 10:58 pci_ep
drwxr-xr-x 2 root root 0 Jul 13 10:58 usb_gadget

$ ls -lrth /sys/kernel/config/pci_ep/functions
total 0
drwxr-xr-x 2 root root 0 Jul 13 10:58 pci_epf_test

$ ls -lrth /sys/kernel/config/pci_ep/controllers
total 0

$
###################################

What is being missed?

Side Queries : Is the controller that is expected to be listed, a
virtual-controller (like the one provided by CONFIG_USB_DUMMY_HCD in
case of USB)?

Or there must be a real additional controller for pci-endpoint purpose?
If yes, then :

              * I guess no listing is expected currently, as my machine has just
                one controller (as pci-host).

              * Is there a way to have an additional virtual pci-controller?


Thanks and Regards,
Ajay

Re: No controller seen in /sys/kernel/config/pci_ep/controllers

[Bjorn Helgaas]

[+to Kishon, endpoint maintainer, +cc LKML]

On Wed, Jul 13, 2022 at 12:53:06PM +0530, Ajay Garg wrote:
> Hello everyone.
> 
> The kernel has been built with :
> 
> ###################################
> CONFIG_PCI_ENDPOINT=y
> CONFIG_PCI_ENDPOINT_CONFIGFS=y
> CONFIG_PCI_EPF_TEST=y
> CONFIG_PCI_ENDPOINT_TEST=y
> ###################################
> 
> 
> Thereafter, following are seen :
> 
> ###################################
> $ sudo mount none /sys/kernel/config/ -t configfs
> mount: /sys/kernel/config: none already mounted or mount point busy.
> 
> $ ls -lrth /sys/class/pci_epc/
> total 0
> 
> $ ls -lrth /sys/kernel/config
> total 0
> drwxr-xr-x 4 root root 0 Jul 13 10:58 pci_ep
> drwxr-xr-x 2 root root 0 Jul 13 10:58 usb_gadget
> 
> $ ls -lrth /sys/kernel/config/pci_ep/functions
> total 0
> drwxr-xr-x 2 root root 0 Jul 13 10:58 pci_epf_test
> 
> $ ls -lrth /sys/kernel/config/pci_ep/controllers
> total 0
> 
> $
> ###################################
> 
> What is being missed?
> 
> Side Queries : Is the controller that is expected to be listed, a
> virtual-controller (like the one provided by CONFIG_USB_DUMMY_HCD in
> case of USB)?
> 
> Or there must be a real additional controller for pci-endpoint purpose?
> If yes, then :
> 
>               * I guess no listing is expected currently, as my machine has just
>                 one controller (as pci-host).
> 
>               * Is there a way to have an additional virtual pci-controller?
> 
> 
> Thanks and Regards,
> Ajay

Re: No controller seen in /sys/kernel/config/pci_ep/controllers

[Ajay Garg]

Any pointers please?

Thanks and Regards,
Ajay

On Wed, Jul 13, 2022 at 11:48 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
>
> [+to Kishon, endpoint maintainer, +cc LKML]
>
> On Wed, Jul 13, 2022 at 12:53:06PM +0530, Ajay Garg wrote:
> > Hello everyone.
> >
> > The kernel has been built with :
> >
> > ###################################
> > CONFIG_PCI_ENDPOINT=y
> > CONFIG_PCI_ENDPOINT_CONFIGFS=y
> > CONFIG_PCI_EPF_TEST=y
> > CONFIG_PCI_ENDPOINT_TEST=y
> > ###################################
> >
> >
> > Thereafter, following are seen :
> >
> > ###################################
> > $ sudo mount none /sys/kernel/config/ -t configfs
> > mount: /sys/kernel/config: none already mounted or mount point busy.
> >
> > $ ls -lrth /sys/class/pci_epc/
> > total 0
> >
> > $ ls -lrth /sys/kernel/config
> > total 0
> > drwxr-xr-x 4 root root 0 Jul 13 10:58 pci_ep
> > drwxr-xr-x 2 root root 0 Jul 13 10:58 usb_gadget
> >
> > $ ls -lrth /sys/kernel/config/pci_ep/functions
> > total 0
> > drwxr-xr-x 2 root root 0 Jul 13 10:58 pci_epf_test
> >
> > $ ls -lrth /sys/kernel/config/pci_ep/controllers
> > total 0
> >
> > $
> > ###################################
> >
> > What is being missed?
> >
> > Side Queries : Is the controller that is expected to be listed, a
> > virtual-controller (like the one provided by CONFIG_USB_DUMMY_HCD in
> > case of USB)?
> >
> > Or there must be a real additional controller for pci-endpoint purpose?
> > If yes, then :
> >
> >               * I guess no listing is expected currently, as my machine has just
> >                 one controller (as pci-host).
> >
> >               * Is there a way to have an additional virtual pci-controller?
> >
> >
> > Thanks and Regards,
> > Ajay

Re: No controller seen in /sys/kernel/config/pci_ep/controllers

[Kishon Vijay Abraham I]

On 21/07/22 15:54, Ajay Garg wrote:
> Any pointers please?
> 
> Thanks and Regards,
> Ajay
> 
> On Wed, Jul 13, 2022 at 11:48 PM Bjorn Helgaas <helgaas@kernel.org> wrote:
>>
>> [+to Kishon, endpoint maintainer, +cc LKML]
>>
>> On Wed, Jul 13, 2022 at 12:53:06PM +0530, Ajay Garg wrote:
>>> Hello everyone.
>>>
>>> The kernel has been built with :
>>>
>>> ###################################
>>> CONFIG_PCI_ENDPOINT=y
>>> CONFIG_PCI_ENDPOINT_CONFIGFS=y
>>> CONFIG_PCI_EPF_TEST=y
>>> CONFIG_PCI_ENDPOINT_TEST=y
>>> ###################################
>>>
>>>
>>> Thereafter, following are seen :
>>>
>>> ###################################
>>> $ sudo mount none /sys/kernel/config/ -t configfs
>>> mount: /sys/kernel/config: none already mounted or mount point busy.
>>>
>>> $ ls -lrth /sys/class/pci_epc/
>>> total 0
>>>
>>> $ ls -lrth /sys/kernel/config
>>> total 0
>>> drwxr-xr-x 4 root root 0 Jul 13 10:58 pci_ep
>>> drwxr-xr-x 2 root root 0 Jul 13 10:58 usb_gadget
>>>
>>> $ ls -lrth /sys/kernel/config/pci_ep/functions
>>> total 0
>>> drwxr-xr-x 2 root root 0 Jul 13 10:58 pci_epf_test
>>>
>>> $ ls -lrth /sys/kernel/config/pci_ep/controllers
>>> total 0
>>>
>>> $
>>> ###################################
>>>
>>> What is being missed?
>>>
>>> Side Queries : Is the controller that is expected to be listed, a
>>> virtual-controller (like the one provided by CONFIG_USB_DUMMY_HCD in
>>> case of USB)?

There are no virtual PCIe endpoint controllers in Linux.
>>>
>>> Or there must be a real additional controller for pci-endpoint purpose?

right, there should be an endpoint controller and the driver for it
should register with the Linux endpoint framework.
>>> If yes, then :
>>>
>>>               * I guess no listing is expected currently, as my machine has just
>>>                 one controller (as pci-host).

correct.
>>>
>>>               * Is there a way to have an additional virtual pci-controller?

Not sure what exactly your use case is. All it's going to need is the
driver to use devm_pci_epc_create() to register a endpoint controller.

You can refer existing endpoint controller drivers
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/controller/cadence/pcie-cadence-ep.c
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/controller/dwc/pcie-designware-ep.c

Thanks,
Kishon

Re: No controller seen in /sys/kernel/config/pci_ep/controllers

[Ajay Garg]

Thank you, that helps.

> Not sure what exactly your use case is.

Nothing complicated, I was stuck on the first step of having the
pci-controller in endpoint-mode :)
Your reply has given me a direction : I will try and find a
hardware/setup wherein I can have a pci-controller in endpoint-mode.


Thanks and Regards,
Ajay