load sdma firmware without udev

[jerry_zeng]

My project uses iMX6 with Linux 4.14.126 by Timesys, but we need to disable udev. How can the sdma-imx6q.bin firmware be loaded from user space without udev? One more question: can the sdma-imx6q.bin firmware be built into Linux kernel image from its source code? if can, please let me know in details.

Thanks,

Jerry

[jerry_zeng]

Hi Igor,

Thank you very much for the quick response. My original general question is how to load iMX6 sdma firmware (sdma-imx6q.bin) from user space without UDEV enabled, and it has nothing to do with Timesys. Can you please specify it?

Thanks,

Jerry

[ceggers1]

Hi Jerry,

modern Linux kernels do not need udev at all for firmware loading. All required functionality is built into the kernel, so no userspace tools are required anymore.

You only have to specify the filename of the SDMA firmware in the device tree node of the SDMA. The firmware file then needs to be placed under /lib/firmware/.

You have to take care, that the firmware is available when the SDMA driver is initialized. I'm not sure what happens if the SDMA driver is linked into the kernel (no module). Maybe the initialization happens before the root fs is mounted and the firmware is not available yet. In my project, I have compiled the SDMA driver as a kernel module which is loaded after the root fs is available.

Technically you could link the SDMA firmware binary into the kernel (as builtin firmware). But in my opinion the license of the SDMA firmware is incompatible to the GPLv2 of the kernel.

I hope that I could answer you questions. If you have further questions about the SDMA, don't hesitate to contact me directly (I don't read the forum every day).

Best regards

Christian

[igorpadykov]

Hi Jerry

may be useful to check Freescale i.MX SDMA tutorial (part I) 

There are no special actions for loading sdma firmware, nxp

linux is performing this automatically. One can try nxp linux from

source.codeaurora.org/external/imx/linux-imx  repository
linux-imx - i.MX Linux kernel 

Best regards
igor

[igorpadykov]

Hi Jerry

sdma is proprietary nxp software its sources are not available for customers.

Regarding timesys linux, it is supported directly by timesys support, issue

may be posted on

TimeSys Linux GPL | Support for TimeSys Linux GPL at SourceForge.net 

Best regards
igor
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