Re: [PATCH] usertools: fix bind failure from dpdk to kernel

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 10 Aug 2022 08:59:15 +0300
Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> wrote:

> On 09/08/2022 14:44, lihuisong (C) wrote:
> > 
> > 在 2022/8/5 23:35, Stephen Hemminger 写道:  
> >> On Fri, 5 Aug 2022 11:10:22 +0800
> >> Huisong Li <lihuisong@huawei.com> wrote:
> >>  
> >>> Currently, the steps for binding device from dpdk driver to kernel
> >>> driver is as follows:
> >>> echo $BDF > /sys/bus/pci/drivers/vfio-pci/unbind
> >>> echo $BDF > /sys/bus/pci/drivers/$kernel_driver/bind
> >>>
> >>> This steps cannot bind device from dpdk driver to kernel driver on
> >>> platform with kernel 5.19. The 'driver_override' must be specify
> >>> kernel driver before binding device to kernel driver.
> >>>
> >>> Fixes: 720b7a058260 ("usertools: fix device binding with kernel tools")
> >>> Cc: stable@dpdk.org
> >>>
> >>> Signed-off-by: Huisong Li <lihuisong@huawei.com>  
> >> Not sure exactly what you did and why.
> >> The patch seems to just remove the check that the driver
> >> is in the set of dpdk_drivers.
> >> .  
> > Currently, the end of the operation binding device from kernel driver to
> > dpdk driver write '\00' to driver_override file so as to this device can
> > be bound to any other driver.   
> 
> This could have work but this was not the way to use the
> driver_override. The kernel ABI document clearly states:
> "and  may be cleared with an empty string (echo > driver_override)."
> Documentation/ABI/testing/sysfs-bus-pci
> 
> Please use the kernel ABI how it is described. Using it in wrong way
> might sometimes work, sometimes not.

No, the kernel ABI is what ever worked before.
The documentation is not the definitive standard.