Re: [PATCH 0/2] Modularization of DFL private feature drivers

[Tom Rix]

Generally i think this is a good approach.

However I do have concern.

The feature_id in dfl is magic number, similar to pci id but without a vendor id.

Is it possible to add something like a vendor id so different vendors would not have to be so careful to use a unique id ?

This touches some of the matching function of the bus ops. Could there be a way for bus ops to be used so that there could be multiple matching function. Maybe the one in 0002 as a default so users could override it ?

The use case I am worrying about is an OEM. The OEM uses an unclaimed feature_id and supplies their own platform device device driver to match the feature_id. But some later version of the kernel claims this feature_id and the OEM's driver no longer works and since the value comes from pci config space it is difficult to change.

So looking for something like

register_feature_matcher((*bus_match)(struct device *dev, struct device_driver *drv))

static int dfl_bus_match_default(struct device *dev, struct device_driver *drv)
{
ÂÂÂ struct dfl_device *dfl_dev = to_dfl_dev(dev);
ÂÂÂ struct dfl_driver *dfl_drv = to_dfl_drv(drv);
ÂÂÂ const struct dfl_device_id *id_entry = dfl_drv->id_table;

ÂÂÂ while (id_entry->feature_id) {
ÂÂÂ ÂÂÂ if (dfl_match_one_device(id_entry, dfl_dev)) {
ÂÂÂ ÂÂÂ ÂÂÂ dfl_dev->id_entry = id_entry;
ÂÂÂ ÂÂÂ ÂÂÂ return 1;
ÂÂÂ ÂÂÂ }
ÂÂÂ ÂÂÂ id_entry++;
ÂÂÂ }

ÂÂÂ return 0;
}

register_feature_matcher(&dfl_bus_match_default)

static int dfl_bus_match(struct device *dev, struct device_driver *drv)
{

ÂÂÂ struct dfl_device *dfl_dev = to_dfl_dev(dev);
ÂÂÂ struct dfl_driver *dfl_drv = to_dfl_drv(drv);
ÂÂÂ const struct dfl_device_id *id_entry = dfl_drv->id_table;

ÂÂÂ while (id_entry->feature_id) {

ÂÂÂ ÂÂÂ matcher = Loop over matchers()

ÂÂÂ ÂÂÂ if (matcher(dev, drv)) {
ÂÂÂ ÂÂÂÂÂÂÂ dfl_dev->id_entry = id_entry;
ÂÂÂ ÂÂÂÂÂÂÂ return 1;
ÂÂÂÂÂÂÂ }
ÂÂÂ ÂÂÂ id_entry++;
ÂÂÂ }

ÂÂÂ return 0;
}

Or maybe use some of the unused bits in the dfl header to add a second vendor-like id and change existing matcher to look feature_id and vendor_like_id.

Tom

Â

On 7/14/20 10:38 PM, Xu Yilun wrote:
> This patchset makes it possible to develop independent driver modules
> for DFL private features. It also helps to leverage existing kernel
> drivers to enable some IP blocks in DFL.
>
> Xu Yilun (2):
>   fpga: dfl: map feature mmio resources in their own feature drivers
>   fpga: dfl: create a dfl bus type to support DFL devices
>
>  Documentation/ABI/testing/sysfs-bus-dfl |  15 ++
>  drivers/fpga/dfl-pci.c                  |  21 +-
>  drivers/fpga/dfl.c                      | 435 +++++++++++++++++++++++++++-----
>  drivers/fpga/dfl.h                      |  91 ++++++-
>  4 files changed, 492 insertions(+), 70 deletions(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-bus-dfl
>