Messages in this thread | | | Subject | Re: [PATCH v2] perf: Support for Arm A32/T32 instruction sets in CoreSight trace | From | Robert Walker <> | Date | Wed, 29 Aug 2018 15:34:16 +0100 |
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Hi Kim,
On 29/08/18 14:49, Kim Phillips wrote: > On Wed, 29 Aug 2018 10:44:23 +0100 > Robert Walker <robert.walker@arm.com> wrote: > >> This patch adds support for generating instruction samples from trace of >> AArch32 programs using the A32 and T32 instruction sets. >> >> T32 has variable 2 or 4 byte instruction size, so the conversion between >> addresses and instruction counts requires extra information from the trace >> decoder, requiring version 0.9.1 of OpenCSD. A check for the new struct >> member has been added to the feature check for OpenCSD. >> >> Signed-off-by: Robert Walker <robert.walker@arm.com> >> --- > ... >> +++ b/tools/build/feature/test-libopencsd.c >> @@ -3,6 +3,13 @@ >> >> int main(void) >> { >> + /* >> + * Requires ocsd_generic_trace_elem.num_instr_range introduced in >> + * OpenCSD 0.9 > 0.9 != 0.9.1 in the above commit text: which is it? I'll change it to 0.9.1 if there's another version of the patch (it was introduced in 0.9, but 0.9.1 has a necessary bug fix) >> + */ >> + ocsd_generic_trace_elem elem; >> + (void)elem.num_instr_range; >> + > This breaks building against older versions of OpenCSD, right? > >> (void)ocsd_get_version(); > Why don't we maintain building against older versions of the library, > and use the version information to make the decision on whether to use > the new feature being introduced in this patch? The intention is to fail the feature detection check if the older version is installed - perf will still compile, but without the CoreSight trace support.
OpenCSD is still in development, so new features like this are being added and it would add a lot of #ifdef mess to the perf code to continue to support any machines with the old library version installed - there will only be a handful of machines affected and it's trivial to upgrade them (the new Debian packages are available). How long would we continue to support such an older version? I also don't see any precedent for supporting multiple dependent library versions in perf. > > Thanks, > > Kim Regards
Rob
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