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Date: Fri, 6 Nov 2020 09:58:28 +0800 From: Leo Yan <leo.yan@...aro.org> To: André Przywara <andre.przywara@....com> Cc: Arnaldo Carvalho de Melo <acme@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Mark Rutland <mark.rutland@....com>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>, James Clark <james.clark@....com>, Dave Martin <Dave.Martin@....com>, Al Grant <Al.Grant@....com>, Wei Li <liwei391@...wei.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH v6 06/21] perf arm-spe: Refactor printing string to buffer Hi Andre, Dave, On Mon, Nov 02, 2020 at 03:50:01PM +0000, André Przywara wrote: [...] > > int arm_spe_pkt_desc(const struct arm_spe_pkt *packet, char *buf, > > size_t buf_len) > > { > > - int ret, ns, el, idx = packet->index; > > + int ns, el, idx = packet->index; > > unsigned long long payload = packet->payload; > > const char *name = arm_spe_pkt_name(packet->type); > > + size_t blen = buf_len; > > + int err = 0; > > > > switch (packet->type) { > > case ARM_SPE_BAD: > > case ARM_SPE_PAD: > > case ARM_SPE_END: > > - return snprintf(buf, buf_len, "%s", name); > > - case ARM_SPE_EVENTS: { > > - size_t blen = buf_len; > > - > > - ret = 0; > > - ret = snprintf(buf, buf_len, "EV"); > > - buf += ret; > > - blen -= ret; > > - if (payload & 0x1) { > > - ret = snprintf(buf, buf_len, " EXCEPTION-GEN"); > > - buf += ret; > > - blen -= ret; > > - } > > - if (payload & 0x2) { > > - ret = snprintf(buf, buf_len, " RETIRED"); > > - buf += ret; > > - blen -= ret; > > - } > > - if (payload & 0x4) { > > - ret = snprintf(buf, buf_len, " L1D-ACCESS"); > > - buf += ret; > > - blen -= ret; > > - } > > - if (payload & 0x8) { > > - ret = snprintf(buf, buf_len, " L1D-REFILL"); > > - buf += ret; > > - blen -= ret; > > - } > > - if (payload & 0x10) { > > - ret = snprintf(buf, buf_len, " TLB-ACCESS"); > > - buf += ret; > > - blen -= ret; > > - } > > - if (payload & 0x20) { > > - ret = snprintf(buf, buf_len, " TLB-REFILL"); > > - buf += ret; > > - blen -= ret; > > - } > > - if (payload & 0x40) { > > - ret = snprintf(buf, buf_len, " NOT-TAKEN"); > > - buf += ret; > > - blen -= ret; > > - } > > - if (payload & 0x80) { > > - ret = snprintf(buf, buf_len, " MISPRED"); > > - buf += ret; > > - blen -= ret; > > - } > > + return arm_spe_pkt_snprintf(&err, &buf, &blen, "%s", name); > > Nothing critical, but in case you need to respin this series for > whatever reason, you might want to use NULL for the first argument, > since you return here and there is little point in setting err. Same for > other cases where you return directly from an arm_spe_pkt_snprintf() call. > But it doesn't hurt, so you could leave it as well, and it's more robust > in case someone extends the code later. Just remind, in the new patch set v7, I don't change to use NULL for the first argument and still pass '&err', the main reason is to consolidate with return value, which is heavily dependent on the 'err' parameter of arm_spe_pkt_snprintf(); the brief form is as follow: switch (type) { ... case ARM_SPE_END: arm_spe_pkt_snprintf(&err, &buf, &blen, "%s", name); break; ... default: break; } handle the 'err'; return err; Please see the new introduced patch [1] so it can give more idea for the changes. Thanks, Leo [1] https://lore.kernel.org/patchwork/patch/1333881/
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