linux-kernel - Re: [PATCH RESEND 0/4] Add support for HiSilicon PCIe Tune and Trace device

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Message-ID: <8735vpf20c.fsf@ashishki-desk.ger.corp.intel.com>
Date:   Sat, 17 Apr 2021 16:56:35 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Yicong Yang <yangyicong@...ilicon.com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        coresight@...ts.linaro.org, linux-pci@...r.kernel.org
Cc:     helgaas@...nel.org, gregkh@...uxfoundation.org,
        lorenzo.pieralisi@....com, will@...nel.org, mark.rutland@....com,
        mathieu.poirier@...aro.org, suzuki.poulose@....com,
        mike.leach@...aro.org, leo.yan@...aro.org,
        jonathan.cameron@...wei.com, song.bao.hua@...ilicon.com,
        john.garry@...wei.com, prime.zeng@...wei.com, liuqi115@...wei.com,
        zhangshaokun@...ilicon.com, yangyicong@...ilicon.com,
        linuxarm@...wei.com, alexander.shishkin@...ux.intel.com
Subject: Re: [PATCH RESEND 0/4] Add support for HiSilicon PCIe Tune and
 Trace device

Yicong Yang <yangyicong@...ilicon.com> writes:

> The reason for not using perf is because there is no current support
> for uncore tracing in the perf facilities.

Not unless you count

$ perf list|grep -ic uncore
77

> We have our own format
> of data and don't need perf doing the parsing.

Perf has AUX buffers, which are used for all kinds of own formats.

> A similar approach for implementing this function is ETM, which use
> sysfs for configuring and a character device for dumping data.

And also perf. One reason ETM has a sysfs interface is because the
driver predates perf's AUX buffers. Can't say if it's the only
reason. I'm assuming you're talking about Coresight ETM.

> Greg has some comments on our implementation and doesn't advocate
> to build driver on debugfs [1]. So I resend this series to
> collect more feedbacks on the implementation of this driver.
>
> Hi perf and ETM related experts, is it suggested to adapt this driver
> to perf? Or is the debugfs approach acceptable? Otherwise use

Aside from the above, I don't think the use of debugfs for kernel ABIs
is ever encouraged.

Regards,
--
Ale