Question about latest skl_dmc_ver1_27.bin and kernel version.

[PKnop]

I am trying to setup Intel's new open-source iHD driver on a Yocto environment.

https://software.intel.com/en-us/articles/build-and-debug-open-source-media-stack

The documentation says that skl_dmc_ver1_27.bin is required. Their documentation updates a symlink (skl_dmc_ver1.bin), as if the kernel loads it, but starting at kernel 4.8, it stopped loading the symlink and instead loads a specific version of the dmc (see here: https://github.com/torvalds/linux/blob/v4.8/drivers/gpu/drm/i915/intel_csr.c#L48). Is the Intel documentation accurate? It is confusing because the guide refers to 4.14.16 specifically, which doesn't use the symlink file skl_dmc_ver1.bin.

Any ways, I tried replacing skl_dmc_ver1_26.bin with skl_dmc_ver1_27.bin to have the same effect, but I got a segfault on boot.

https://pastebin.com/amW9vDdC

Should I even bother updating the DMC? Should the iHD driver work on most kernels, even with 1_26 version of DMC?

By the way, this is the kernel I am using (with Yocto).

https://github.com/intel/linux-intel-lts/tree/4.14/yocto/base/drivers/gpu/drm/i915

Any help would be greatly appreciated. There is no documentation on this stuff.

[TurtleCrazy]

The documentation says that skl_dmc_ver1_27.bin is required.

Maybe the documentation has changed since your post was published, but, here and now, the documentation requires the 1.26 version.

Their documentation updates a symlink (skl_dmc_ver1.bin), as if the kernel loads it, but starting at kernel 4.8,

it stopped loading the symlink

and instead loads a specific version of the dmc (see here: https://github.com/torvalds/linux/blob/v4.8/drivers/gpu/drm/i915/intel_c.).

#define I915_CSR_SKL "i915/skl_dmc_ver1_26.bin" 
MODULE_FIRMWARE(I915_CSR_SKL); 
#define SKL_CSR_VERSION_REQUIRED CSR_VERSION(1, 26) 

Good point. The symlink sounds useless since this i915 patch was released.