On Mon, Jan 23, 2023 at 8:32 AM Vincent Whitchurch
<vincent.whitchurch@xxxxxxxx> wrote:
>
> Add a PCI driver which registers all child nodes specified in the
> devicetree. It will allow platform devices to be used on virtual
> systems which already support PCI and devicetree, such as UML with
> virt-pci.
There's similar work underway for Xilinx/AMD PCIe FPGAs[1]. It's the
same thing really. Non-discoverable things downstream of a PCI device.
There's also a desire for that to work on non-DT (ACPI) based hosts.
While UML supports DT, that's currently only for the unittest AFAIK.
So it's more like a non-DT host. How does the DT get populated for UML
for this to work?
Can you provide details on the actual h/w you want to use. What
problem are you trying to solve?
Really, what I want to see here is everyone interested in this feature
to work together on it. Not just creating a one-off solution for their
1 use case that's a subset of a bigger solution.
> The driver has no id_table by default; user space needs to provide one
> using the new_id mechanism in sysfs.
But your DT will have the id in it already. Wouldn't you rather
everything work without userspace intervention? I can't imagine the
list here would be too long.
>
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx>
> ---
> drivers/mfd/Kconfig | 11 +++++++++++
> drivers/mfd/Makefile | 1 +
> drivers/mfd/simple-mfd-pci.c | 21 +++++++++++++++++++++
> 3 files changed, 33 insertions(+)
>
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 30db49f31866..1e325334e9ae 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -1277,6 +1277,17 @@ config MFD_SIMPLE_MFD_I2C
> sub-devices represented by child nodes in Device Tree will be
> subsequently registered.
>
> +config MFD_SIMPLE_MFD_PCI
> + tristate "Simple Multi-Functional Device support (PCI)"
> + depends on PCI
> + depends on OF || COMPILE_TEST
> + help
> + This enables support for a PCI driver for which any sub-devices
> + represented by child nodes in the devicetree will be registered.
> +
> + The driver does not bind to any devices by default; that should
> + be done via sysfs using new_id.
> +
> config MFD_SL28CPLD
> tristate "Kontron sl28cpld Board Management Controller"
> depends on I2C
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index 457471478a93..7ae329039a13 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -268,6 +268,7 @@ obj-$(CONFIG_MFD_QCOM_PM8008) += qcom-pm8008.o
>
> obj-$(CONFIG_SGI_MFD_IOC3) += ioc3.o
> obj-$(CONFIG_MFD_SIMPLE_MFD_I2C) += simple-mfd-i2c.o
> +obj-$(CONFIG_MFD_SIMPLE_MFD_PCI) += simple-mfd-pci.o
> obj-$(CONFIG_MFD_SMPRO) += smpro-core.o
> obj-$(CONFIG_MFD_INTEL_M10_BMC) += intel-m10-bmc.o
>
> diff --git a/drivers/mfd/simple-mfd-pci.c b/drivers/mfd/simple-mfd-pci.c
> new file mode 100644
> index 000000000000..c5b2540e924a
> --- /dev/null
> +++ b/drivers/mfd/simple-mfd-pci.c
> @@ -0,0 +1,21 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#include <linux/module.h>
> +#include <linux/of_platform.h>
> +#include <linux/pci.h>
> +
> +static int simple_mfd_pci_probe(struct pci_dev *pdev,
> + const struct pci_device_id *id)
> +{
> + return devm_of_platform_populate(&pdev->dev);
Really, this could be anything in the child DT. Not just what Linux
classifies as an MFD. So maybe drivers/mfd is not the right place.
Rob
[1] https://lore.kernel.org/all/1674183732-5157-1-git-send-email-lizhi.hou@xxxxxxx/
