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Message-ID: <2c440398-fc03-4e26-a471-2c1a742b95c0@oss.qualcomm.com>
Date: Fri, 23 Jan 2026 09:32:26 +0800
From: Jie Gan <jie.gan@....qualcomm.com>
To: Suzuki K Poulose <suzuki.poulose@....com>,
Mike Leach <mike.leach@...aro.org>,
James Clark <james.clark@...aro.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>,
Tingwei Zhang <tingwei.zhang@....qualcomm.com>,
Mao Jinlong <jinlong.mao@....qualcomm.com>,
Bjorn Andersson <andersson@...nel.org>,
Konrad Dybcio <konradybcio@...nel.org>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
devicetree@...r.kernel.org
Subject: Re: [PATCH v10 3/8] coresight: tmc: Introduce sysfs_read_ops to wrap
sysfs read operations
On 1/22/2026 6:07 PM, Suzuki K Poulose wrote:
> On 22/01/2026 02:08, Jie Gan wrote:
>> Introduce sysfs_read_ops as a wrapper, wrap sysfs read operations, for
>> reading
>> trace data from the TMC buffer.
>>
>> Reviewed-by: Mike Leach <mike.leach@...aro.org>
>> Signed-off-by: Jie Gan <jie.gan@....qualcomm.com>
>> ---
>> drivers/hwtracing/coresight/coresight-tmc-core.c | 50 ++++++++++
>> +-------------
>> drivers/hwtracing/coresight/coresight-tmc.h | 17 ++++++++
>> 2 files changed, 40 insertions(+), 27 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc-core.c b/
>> drivers/hwtracing/coresight/coresight-tmc-core.c
>> index 1ea255ffa67c..8b0397a77e57 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-tmc-core.c
>> @@ -232,17 +232,10 @@ static int tmc_read_prepare(struct tmc_drvdata
>> *drvdata)
>> {
>> int ret = 0;
>> - switch (drvdata->config_type) {
>> - case TMC_CONFIG_TYPE_ETB:
>> - case TMC_CONFIG_TYPE_ETF:
>> - ret = tmc_read_prepare_etb(drvdata);
>> - break;
>> - case TMC_CONFIG_TYPE_ETR:
>> - ret = tmc_read_prepare_etr(drvdata);
>> - break;
>> - default:
>> + if (drvdata->sysfs_ops)
>> + ret = drvdata->sysfs_ops->read_prepare(drvdata);
>> + else
>> ret = -EINVAL;
>> - }
>> if (!ret)
>> dev_dbg(&drvdata->csdev->dev, "TMC read start\n");
>> @@ -254,17 +247,10 @@ static int tmc_read_unprepare(struct tmc_drvdata
>> *drvdata)
>> {
>> int ret = 0;
>> - switch (drvdata->config_type) {
>> - case TMC_CONFIG_TYPE_ETB:
>> - case TMC_CONFIG_TYPE_ETF:
>> - ret = tmc_read_unprepare_etb(drvdata);
>> - break;
>> - case TMC_CONFIG_TYPE_ETR:
>> - ret = tmc_read_unprepare_etr(drvdata);
>> - break;
>> - default:
>> + if (drvdata->sysfs_ops)
>> + ret = drvdata->sysfs_ops->read_unprepare(drvdata);
>> + else
>> ret = -EINVAL;
>> - }
>> if (!ret)
>> dev_dbg(&drvdata->csdev->dev, "TMC read end\n");
>> @@ -291,13 +277,8 @@ static int tmc_open(struct inode *inode, struct
>> file *file)
>> static ssize_t tmc_get_sysfs_trace(struct tmc_drvdata *drvdata,
>> loff_t pos, size_t len,
>> char **bufpp)
>> {
>> - switch (drvdata->config_type) {
>> - case TMC_CONFIG_TYPE_ETB:
>> - case TMC_CONFIG_TYPE_ETF:
>> - return tmc_etb_get_sysfs_trace(drvdata, pos, len, bufpp);
>> - case TMC_CONFIG_TYPE_ETR:
>> - return tmc_etr_get_sysfs_trace(drvdata, pos, len, bufpp);
>> - }
>> + if (drvdata->sysfs_ops)
>> + return drvdata->sysfs_ops->get_trace_data(drvdata, pos, len,
>> bufpp);
>
> minor nit: Please could we bail out in tmc_open() if the drvdata-
> >sysfs_ops is not set. That way, we don't have to sprinkle it
> everywhere. And also, we don't expect to see this case anyways.
>
In tmc_open, we already have checked the validation of the
drvdata->sysfs_ops, we dont need check it again here. I will fix it in
next version.
>> return -EINVAL;
>> }
>> @@ -769,6 +750,18 @@ static void register_crash_dev_interface(struct
>> tmc_drvdata *drvdata,
>> "Valid crash tracedata found\n");
>> }
>> +static const struct sysfs_read_ops tmc_etb_sysfs_read_ops = {
>
> minor nit: please could we rename the struct type to :
>
> struct tmc_sysfs_ops
>
> and then use
>
> etb_sysfs_ops = {}
> etr_sysfs_ops = {}
>
>
> Rest looks fine to me
>
Well noted. Will fix it in next version.
Thanks,
Jie
> Suzuki
>
>> + .read_prepare = tmc_read_prepare_etb,
>> + .read_unprepare = tmc_read_unprepare_etb,
>> + .get_trace_data = tmc_etb_get_sysfs_trace,
>> +};
>> +
>> +static const struct sysfs_read_ops tmc_etr_sysfs_read_ops = {
>> + .read_prepare = tmc_read_prepare_etr,
>> + .read_unprepare = tmc_read_unprepare_etr,
>> + .get_trace_data = tmc_etr_get_sysfs_trace,
>> +};
>> +
>> static int __tmc_probe(struct device *dev, struct resource *res)
>> {
>> int ret = 0;
>> @@ -828,6 +821,7 @@ static int __tmc_probe(struct device *dev, struct
>> resource *res)
>> desc.subtype.sink_subtype = CORESIGHT_DEV_SUBTYPE_SINK_BUFFER;
>> desc.ops = &tmc_etb_cs_ops;
>> dev_list = &etb_devs;
>> + drvdata->sysfs_ops = &tmc_etb_sysfs_read_ops;
>> break;
>> case TMC_CONFIG_TYPE_ETR:
>> desc.groups = coresight_etr_groups;
>> @@ -841,6 +835,7 @@ static int __tmc_probe(struct device *dev, struct
>> resource *res)
>> mutex_init(&drvdata->idr_mutex);
>> dev_list = &etr_devs;
>> INIT_LIST_HEAD(&drvdata->etr_buf_list);
>> + drvdata->sysfs_ops = &tmc_etr_sysfs_read_ops;
>> break;
>> case TMC_CONFIG_TYPE_ETF:
>> desc.groups = coresight_etf_groups;
>> @@ -849,6 +844,7 @@ static int __tmc_probe(struct device *dev, struct
>> resource *res)
>> desc.subtype.link_subtype = CORESIGHT_DEV_SUBTYPE_LINK_FIFO;
>> desc.ops = &tmc_etf_cs_ops;
>> dev_list = &etf_devs;
>> + drvdata->sysfs_ops = &tmc_etb_sysfs_read_ops;
>> break;
>> default:
>> pr_err("%s: Unsupported TMC config\n", desc.name);
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/
>> hwtracing/coresight/coresight-tmc.h
>> index 9b3c4e6f0a5e..c9a82ff6cd00 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc.h
>> +++ b/drivers/hwtracing/coresight/coresight-tmc.h
>> @@ -221,6 +221,8 @@ struct etr_buf_node {
>> struct list_head node;
>> };
>> +struct sysfs_read_ops;
>> +
>> /**
>> * struct tmc_drvdata - specifics associated to an TMC component
>> * @atclk: optional clock for the core parts of the TMC.
>> @@ -258,6 +260,7 @@ struct etr_buf_node {
>> * Used by ETR/ETF.
>> * @etr_buf_list: List that is used to manage allocated etr_buf.
>> * @reading_node: Available buffer_node for byte-cntr reading.
>> + * @sysfs_ops: Read operations for sysfs mode.
>> */
>> struct tmc_drvdata {
>> struct clk *atclk;
>> @@ -290,6 +293,20 @@ struct tmc_drvdata {
>> struct tmc_resrv_buf crash_mdata;
>> struct list_head etr_buf_list;
>> struct etr_buf_node *reading_node;
>> + const struct sysfs_read_ops *sysfs_ops;
>> +};
>> +
>> +/**
>> + * struct sysfs_read_ops - read operations for TMC and its helper
>> devices
>> + * @read_prepare: prepare operation.
>> + * @read_unprepare: unprepare operation.
>> + * @get_trace_data: read operation.
>> + */
>> +struct sysfs_read_ops {
>> + int (*read_prepare)(struct tmc_drvdata *drvdata);
>> + int (*read_unprepare)(struct tmc_drvdata *drvdata);
>> + ssize_t (*get_trace_data)(struct tmc_drvdata *drvdata, loff_t pos,
>> + size_t len, char **bufpp);
>> };
>> struct etr_buf_operations {
>>
>
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