Let libipchw consumers drop vendor HALs they can never run on

[widgetii]

libipchw carries a HAL for every supported vendor. They are only reachable through the detection table in chipid.c, so a consumer that already knows its SoC family links a pile of code that can never execute.

--gc-sections does not help here — manufacturers[] is a static array of function pointers, so every entry stays referenced no matter what the linker does. The only way to drop them is to not compile them.

Change

New cache variable IPCHW_VENDORS selects which optional HALs go into the library:

• all — default, behaviour and output unchanged
• none — HiSilicon only
• a ;-separated subset, e.g. -DIPCHW_VENDORS="sstar;xm"

The HiSilicon HAL is always built, because hw_detect_system() dispatches to it directly rather than through the table.

The ipctool executable is a diagnostic tool that has to run on anything, so it always compiles every vendor regardless of the setting.

Measurements

ARM Release build:

IPCHW_VENDORS	ipcinfo	libipchw.a	ipctool
all (default)	96,208	150,060	263,456
sstar;xm	91,728	112,340	263,456
none	87,456	103,064	263,456

none takes 8,752 bytes (9.1%) off ipcinfo. ipctool is unchanged across all three, as intended.

Building with the default all produces a byte-identical result to before this change.

Notes on the implementation

• chipid.c gets a sentinel entry plus a detect_fn check in the loop, so manufacturers[] stays a well-formed non-empty array when every optional vendor is compiled out.
• ipcinfo's print_serial() guards its sstar_get_die_id() call. That is a direct dependency from a library consumer on a HAL that may no longer be present — worth knowing it exists.
• Vendor HALs turned out to be referenced from exactly one place in the library (chipid.c) plus their own implementation file, which is why this stays small.

Testing

Cross-built for ARM in all three configurations above; ipcinfo and ipctool both link cleanly in each.

Verified on a Hi3516EV300 + IMX335 that detection is unaffected — ipcinfo -c/-f/-s/-t report identical values built with all and with none:

chip=hi3516ev300  family=hi3516ev200  sensor=imx335  temp=73.93

🤖 Generated with Claude Code