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Resolve a handle's driver functions once, at open - #71
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read, write, ioctl and flush looked up the driver's DIF function (Dmod_GetDifFunction(), comparing signatures) on every call; an audio stream writes hundreds of times a second through two nodes. They are resolved when the file is opened and kept in its handle. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Summary
fread,fwrite,ioctl,flushandsynclooked up the driver's DIF function withDmod_GetDifFunction()on every call, which compares signature strings. An audio stream writes hundreds of times a second through two nodes (the codec, then its SAI), and a profile on the STM32F746G-DISCO showed the signature comparisons as a visible share of the audio service's CPU.The functions are now resolved once, when the file is opened, and kept in the handle. The handle keeps its driver node for its lifetime. It is zeroed at allocation, so
/dev/nullhandles hold NULLs.The file-system layer above already caches its own DIF functions (dmvfs#61); this is the same for the driver layer below.
Test plan
ctestwith-DDMDEVFS_BUILD_TESTS=ON: everything passes excepttest_dmdevmon, which fails on main as well (test_orderalso fails there now and then)🤖 Generated with Claude Code