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charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org [AMD Official Use Only - General] > -----Original Message----- > From: Robin Murphy > Sent: Wednesday, August 3, 2022 7:46 PM > To: Gupta, Nipun ; linux-kernel@vger.kernel.org; > linux-arm-kernel@lists.infradead.org; gregkh@linuxfoundation.org; > rafael@kernel.org; maz@kernel.org; tglx@linutronix.de > Cc: okaya@kernel.org; Anand, Harpreet ; > Simek, Michal ; Agarwal, Nikhil > > Subject: Re: [RFC PATCH 0/2] add support for CDX bus MSI domain > > [CAUTION: External Email] > > 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? According to our analysis, device tree modification via OF_DYNAMIC is mostly designed as a boot time patching mechanism but it was never designed to be runtime used as a "bus" mechanism. Most firmware patches ACPI/DT during boot but we want to go beyond boot time configuration and would like to be able to dynamically remove/insert objects during FPGA servicing. As an example, a new FPGA can be programmed to the system where either the attributes are changed or new devices are introduced. Another concern about OF_DYNAMIC is about security. We'd like to keep device-tree contents intact at boot and never touch again as a good security principle. > > 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 > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel