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SubjectRe: [RESEND PATCH V12 XDMA 1/2] dmaengine: xilinx: xdma: Add xilinx xdma driver
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On 21. 02. 23 22:06, Geert Uytterhoeven wrote:
> Hi Martin,
>
> On Tue, Feb 21, 2023 at 9:45 PM Martin Tůma <tumic@gpxsee.org> wrote:
>> On 21. 02. 23 14:25, Geert Uytterhoeven wrote:
>>> No platform dependencies at all, while this is a platform driver that
>>> relies on some other not-yet-existing driver creating an "xdma"
>>> platform device?
>>
>> There is at least one "already-existing" driver based on this driver
>> that is waiting in the v4l2 queue for xdma - our MGB4 driver:
>> https://patchwork.kernel.org/project/linux-media/patch/20230207150119.5542-2-tumic@gpxsee.org/
>
> Thanks for the link!
>
> As VIDEO_MGB4 selects XILINX_XDMA, perhaps XILINX_XDMA
> can be made invisible, unless compile-testing?
>
> config XILINX_XDMA
> tristate "Xilinx DMA/Bridge Subsystem DMA Engine" if COMPILE_TEST
>
> Gr{oetje,eeting}s,
>
> Geert
>

Hi,
I think that the XDMA driver will always be used by a superior PCIe card
driver like in our case (mgb4) and using it separately makes no sense/is
not possible, so disabling it until some of the superior drivers selects
it makes sense for me. But what about out-of-the-tree modules based on
xdma? Making the module "invisible" will make compile them much harder I
guess? And there will be proprietary drivers based on xdma, see Xilinx
XRT: https://github.com/houlz0507/XRT-1/tree/xdma_v4_usage

The xdma authors from Xilinx will definitely give you a more
authoritative answer. I'm just a "random" user of the xdma module.
Originally our mgb4 driver was based on our own xdma sub-driver (in turn
based on some old "test" driver from Xilinx) which I was glad we could
abandon when this xdma driver has appeared. I helped the xdma module to
become usable for PCIe cards like our v4l2 grabber, but the original
intents of the xdma driver are unknown to me. If it is XRT, than Xilinx
will probably like the module to stay visible.

M.

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