On Tue, Jun 14, 2016 at 11:02:29AM +0200, Lars-Peter Clausen wrote: > > > > ACPI has device tables which describe the devices which are not > > discoverable. (not everything in x86 is discoverable) > > > > Yes these are hard coded in BIOS, but if you are connecting > > FPGA and providing additional functionality then BIOS update would be > > required to describe all these > > The FPGA is on a PCIe card. PCIe cards are autodetected and not hardcoded in > the BIOS table. Can we detect the devices on the FPGA as well, my guess is No. And isn't the BIOS updated for FPGAs? BIOS tables are per board, same as DT entries you would write for a card. Even for discoverable devices, DSDT provides methods to read data. > For this problem there are basically two approaches. > > 1) Extend all used drivers for the used peripherals with platform data > support. Then write a PCIe driver which instantiates all the drivers for the > peripherals found on the board and in the FPGA using platform devices and > platform data. The problem with platform devices is that they require pdata and I do not see a scalable way to do pdata > 2) Use DT overlays. This does not require any changes to any of the existing > peripheral drivers already supporting DT. The way this works is you create a > DT snippet that describes the peripherals on your PCIe card and then write a > simple PCIe driver that loads the DT blob for said snippet when the card is > detected. > > This does not yet work in the upstream kernel, but it is the preferred > approach and multiple people are working on getting a solution for this > upstream. E.g. see https://github.com/mfornero/linux/commits/dtbo_wip OTOH that does sounds bit better. But this also seems like shoving DT on x86, akin to someone forcing you to use ACPI as they have toolsets and prefer to use that. Finally as long as data is being discovered and not hard coded in kernel, I really don't mind either way! It just means to an end! Thanks -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
