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From:   Alexander Shishkin <alexander.shishkin@linux.intel.com>
To:     Yicong Yang <yangyicong@hisilicon.com>,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        coresight@lists.linaro.org, linux-pci@vger.kernel.org
Cc:     helgaas@kernel.org, gregkh@linuxfoundation.org,
        lorenzo.pieralisi@arm.com, will@kernel.org, mark.rutland@arm.com,
        mathieu.poirier@linaro.org, suzuki.poulose@arm.com,
        mike.leach@linaro.org, leo.yan@linaro.org,
        jonathan.cameron@huawei.com, song.bao.hua@hisilicon.com,
        john.garry@huawei.com, prime.zeng@huawei.com, liuqi115@huawei.com,
        zhangshaokun@hisilicon.com, yangyicong@hisilicon.com,
        linuxarm@huawei.com, alexander.shishkin@linux.intel.com
Subject: Re: [PATCH RESEND 0/4] Add support for HiSilicon PCIe Tune and
 Trace device
In-Reply-To: <1618654631-42454-1-git-send-email-yangyicong@hisilicon.com>
References: <1618654631-42454-1-git-send-email-yangyicong@hisilicon.com>
Date:   Sat, 17 Apr 2021 16:56:35 +0300
Message-ID: <8735vpf20c.fsf@ashishki-desk.ger.corp.intel.com>
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Yicong Yang <yangyicong@hisilicon.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