linux-kernel - Re: [RFC PATCH 0/2] add support for CDX bus MSI domain

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Message-ID: <846c663a-5999-977b-8a69-89c8ca522cea@arm.com>
Date:   Wed, 3 Aug 2022 15:16:11 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Nipun Gupta <nipun.gupta@....com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, gregkh@...uxfoundation.org,
        rafael@...nel.org, maz@...nel.org, tglx@...utronix.de
Cc:     okaya@...nel.org, harpreet.anand@....com, michal.simek@....com,
        nikhil.agarwal@....com
Subject: Re: [RFC PATCH 0/2] add support for CDX bus MSI domain

On 2022-08-03 13:26, Nipun Gupta wrote:
> Devices in FPGA can be added/modified dynamically on run-time.
> These devices are exposed on system bus to embedded CPUs.
> 
> CDX is an upcoming bus, that caters to the requirement for
> dynamically discovered FPGA devices. These devices are added
> as platform devices where fwnode is created using 'software
> nodes' in Linux framework.
> 
> This RFC targets to solves 2 issues when adding devices
> dynamically using platform_device_register API.
> 
> 1. It creates a MSI domain for CDX bus devices, which can
>     discover device ID used by GIC ITS without depending
>     on of_node.
> 2. Since these devices are not present in device tree, it
>     creates a sysfs entry to expose the compatible string.

Isn't this pretty much what CONFIG_OF_DYNAMIC is for? From the look of 
these patches this thing is still completely tied to devicetree, so why 
reinvent that wheel?

Robin.

> Nipun Gupta (2):
>    irqchip: cdx-bus: add cdx-MSI domain with gic-its domain as parent
>    driver core: add compatible string in sysfs for platform devices
> 
>   drivers/base/platform.c                  |  15 +++
>   drivers/irqchip/Makefile                 |   1 +
>   drivers/irqchip/irq-gic-v3-its-cdx-msi.c | 114 +++++++++++++++++++++++
>   include/linux/cdx/cdx.h                  |  15 +++
>   4 files changed, 145 insertions(+)
>   create mode 100644 drivers/irqchip/irq-gic-v3-its-cdx-msi.c
>   create mode 100644 include/linux/cdx/cdx.h
>