linux-kernel - Re: [PATCH v6 09/13] Add nodes for dsb edge control

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Date:   Tue, 20 Jun 2023 16:31:59 +0800
From:   Tao Zhang <quic_taozha@...cinc.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Konrad Dybcio <konradybcio@...il.com>,
        Mike Leach <mike.leach@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jinlong Mao <quic_jinlmao@...cinc.com>,
        Leo Yan <leo.yan@...aro.org>, <coresight@...ts.linaro.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
        Tingwei Zhang <quic_tingweiz@...cinc.com>,
        Yuanfang Zhang <quic_yuanfang@...cinc.com>,
        Trilok Soni <quic_tsoni@...cinc.com>,
        Hao Zhang <quic_hazha@...cinc.com>,
        <linux-arm-msm@...r.kernel.org>, <andersson@...nel.org>
Subject: Re: [PATCH v6 09/13] Add nodes for dsb edge control


On 6/20/2023 3:37 PM, Greg Kroah-Hartman wrote:
> On Tue, Jun 20, 2023 at 03:32:37PM +0800, Tao Zhang wrote:
>> Add the nodes to set value for DSB edge control and DSB edge
>> control mask. Each DSB subunit TPDM has maximum of n(n<16) EDCR
>> resgisters to configure edge control. DSB edge detection control
>> 00: Rising edge detection
>> 01: Falling edge detection
>> 10: Rising and falling edge detection (toggle detection)
>> And each DSB subunit TPDM has maximum of m(m<8) ECDMR registers to
>> configure mask. Eight 32 bit registers providing DSB interface
>> edge detection mask control.
>>
>> Signed-off-by: Tao Zhang <quic_taozha@...cinc.com>
>> ---
>>   .../ABI/testing/sysfs-bus-coresight-devices-tpdm   |  32 +++++
>>   drivers/hwtracing/coresight/coresight-tpdm.c       | 143 ++++++++++++++++++++-
>>   drivers/hwtracing/coresight/coresight-tpdm.h       |  22 ++++
>>   3 files changed, 196 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
>> index 2a82cd0..34189e4a 100644
>> --- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
>> +++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-tpdm
>> @@ -60,3 +60,35 @@ Description:
>>   		Bit[3] : Set to 0 for low performance mode.
>>   				 Set to 1 for high performance mode.
>>   		Bit[4:8] : Select byte lane for high performance mode.
>> +
>> +What:		/sys/bus/coresight/devices/<tpdm-name>/dsb_edge_ctrl
>> +Date:		March 2023
>> +KernelVersion	6.5
>> +Contact:	Jinlong Mao (QUIC) <quic_jinlmao@...cinc.com>, Tao Zhang (QUIC) <quic_taozha@...cinc.com>
>> +Description:
>> +		Read/Write a set of the edge control registers of the DSB
>> +		in TPDM.
>> +
>> +		Expected format is the following:
>> +		<integer1> <integer2> <integer3>
> sysfs is "one value", not 3.  Please never have to parse a sysfs file.

Do you mean sysfs file can only accept "one value"?

I see that more than one value are written to the sysfs file 
"trigout_attach".

>
>> +static ssize_t dsb_edge_ctrl_show(struct device *dev,
>> +				       struct device_attribute *attr,
>> +				       char *buf)
>> +{
>> +	struct tpdm_drvdata *drvdata = dev_get_drvdata(dev->parent);
>> +	ssize_t size = 0;
>> +	unsigned long bytes;
>> +	int i;
>> +
>> +	spin_lock(&drvdata->spinlock);
>> +	for (i = 0; i < TPDM_DSB_MAX_EDCR; i++) {
>> +		bytes = sysfs_emit_at(buf, size,
>> +				  "Index:0x%x Val:0x%x\n", i,
> Again, no, one value, no "string" needed to parse anything.

I also see other sysfs files can be read more than one value in other 
drivers.

Is this "one value" limitation the usage rule of Linux sysfs system?

Or am I misunderstanding what you mean?


Best,

Tao

>
> greg k-h