Changing firmware directory

[Gelbpunkt]

Hi, I would like to propose moving away from /usr/share/qcom and using the device-specific /usr/lib/firmware directory instead.

There are multiple reasons for this:

• We can much easier guess the directory by simply checking any firmware-name properties in the devicetree and constructing a new path relative to those. The current guessing mechanism tends to work well, but it is unnecessarily complex due to hexagonrpcd's own conventions. It also breaks on at least one case known to me, when the model name does not start with the manufacturer name: The Fairphone (Gen 6) would result in manufacturer name guessed as The, which cannot trivially be solved
• The FHS says that /usr/share is for "architecture independent data files" (https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch04s11.html) - the HexagonFS files contain Hexagon ELF files, which are technically not just data files, they are firmware and architecture-specific. Some Linux distributions even have checks to disallow ELF files in /usr/share due to this

I suggested this on Matrix a while ago to @flamingradian and they suggested I should open an issue here or check with @lumag in chat. Please let me know what your thoughts on this are, I'd be happy to implement this change.

[lumag]

/usr/lib/firmware is for the firmware files which are loaded by the kernel. Hexagon DSP libs are not the firmware. They are the libraries which are loaded onto the DSP on demand by the userspace daemon and other userspace apps. The Hexagon DSP ELF files are not specific for the host arch, so it should not be a problem from the FHS point of view.

[lumag]

Also, you don't have to use the full market name there. For FP6 the dir should be /usr/share/qcom/milos/Fairphone/FP6

[Gelbpunkt]

Also, you don't have to use the full market name there. For FP6 the dir should be /usr/share/qcom/milos/Fairphone/FP6

Not /usr/share/qcom/milos/Fairphone/fp6? The codename is lowercase IIRC.

Either way, the problem is still that it can't be guessed at runtime. If the model property in the devicetree is the full market name, it currently can't be guessed properly on the FP6.

[lumag]

Also, you don't have to use the full market name there. For FP6 the dir should be /usr/share/qcom/milos/Fairphone/FP6

Not /usr/share/qcom/milos/Fairphone/fp6? The codename is lowercase IIRC.

There is no such requirement. See https://github.com/linux-msm/hexagon-dsp-binaries

Either way, the problem is still that it can't be guessed at runtime. If the model property in the devicetree is the full market name, it currently can't be guessed properly on the FP6.

The FastRPC team is working on the config file, which will map models to SoC, Vendor and device names. I suggest following the same approach (or even reusing the same config). It might make sense even to allow conf.d apprach, adding device configurations from different sorces.

[z3ntu]

Hi, I'm actually currently trying to get hexagonrpcd running on The Fairphone (Gen. 6) and am precicely hitting the issue described by @Gelbpunkt:

openat(AT_FDCWD, "/proc/device-tree/compatible", O_RDONLY|O_LARGEFILE) = 3
fstat(3, {st_mode=S_IFREG|0444, st_size=25, ...}) = 0
read(3, "fairphone,fp6\0qcom,milos\0", 25) = 25
close(3)                                = 0
openat(AT_FDCWD, "/proc/device-tree/model", O_RDONLY|O_LARGEFILE) = 3
fstat(3, {st_mode=S_IFREG|0444, st_size=23, ...}) = 0
read(3, "The Fairphone (Gen. 6)\0", 23) = 23
close(3)                                = 0
faccessat(AT_FDCWD, "/usr/share/qcom/milos/The/fp6", R_OK) = -1 ENOENT (No such file or directory)
faccessat(AT_FDCWD, "/usr/share/qcom/milos/The/milos", R_OK) = -1 ENOENT (No such file or directory)

If still the desired way of doing it is what you described, then at least the heuristics need to be updated to support this case. Maybe split the model by space and search until you find one that sorta matches the first vendor part of the compatble, so probably case insensitive matching? Then vendor wouldn't be The but Fairphone. Marketing departments are always cleverer than simple heuristics ;)

But I also don't quite get why you wouldn't just split the device compatible by the command use /usr/share/qcom/fairphone/fp6/, which wouldn't need any guessing or heuristics really.

[lumag]

Just to note: we are landing a YAML file format, describing mappings from the machine name to the subdir. It is expected that sideloaded binaries will also install similar files, allowing FastRPC to locate bins. I think it can be used by hexagonrpcd too.

See linux-msm/hexagon-dsp-binaries#36