From: johannes@gnu-linux.rocks
To: kernelnewbies@kernelnewbies.org
Subject: Getting a DMA channel on x86 for a PCIe transfer
Date: Tue, 8 Aug 2023 18:01:15 +0200 [thread overview]
Message-ID: <20230808160115.10510-1-johannes@gnu-linux.rocks> (raw)
Hi,
I want to transfer data from the RAM to a BAR with memory space of a PCIe Endpoint over a DMA on a x86 System.
But currently I am failing to get a channel of a DMA controller.
In the probe function, I tried to requst a DMA channel with:
dma_cap_zero(mask);
dma_cap_set(DMA_SLAVE | DMA_PRIVATE, mask);
chan = dma_request_channel(mask, NULL, NULL);
and also with:
chan = dma_request_chan(&pdev->dev, pci_name(pdev));
But in both cases IS_ERR_OR_NULL(chn) is true, so I am not getting a valid DMA channel.
What am I doing wrong? How to get a DMA channel on a x86 system?
Best regards,
Johannes
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