Re: [PATCH] coresight: etm4x: fix mis-usage of nr_resource in sysfs interface

Jonathan Zhou
2020-09-09T06:21:01Z

Hi Mathieu,
Thanks for reply.

On 09/09/2020 01:35, Mathieu Poirier wrote:
> On Fri, Sep 04, 2020 at 06:08:46PM +0800, Zhouwen (Jonathan, Turing) wrote:
>>
>> Hi Mathieu,
>>
>> Thanks for your review.
>>
>> 在 2020/9/4 1:22, Mathieu Poirier 写道:
>>> On Wed, Sep 02, 2020 at 03:52:56PM +0800, Jonathan Zhou wrote:
>>>> The member @nr_resource represents how many resource selector pairs,
>>>> and the pair 0 is always implemented and reserved.
>>>> So let's multiply by 2 when displaying the implemented resource seletors
>>>> and resetting the seletor configuration .
>>>> And also update the validation of the input @idx.
>>>>
>>>> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
>>>> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
>>>> Cc: Mike Leach <mike.leach@linaro.org>
>>>> Cc: Shaokun Zhang <zhangshaokun@hisilicon.com>
>>>> Cc: lizixian@hisilicon.com
>>>> Signed-off-by: Jonathan Zhou <jonathan.zhouwen@huawei.com>
>>>> ---
>>>> drivers/hwtracing/coresight/coresight-etm4x-sysfs.c | 15 ++++++++++-----
>>>> 1 file changed, 10 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
>>>> index b673e738bc9a..635b93d20efa 100644
>>>> --- a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
>>>> +++ b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
>>>> @@ -143,8 +143,10 @@ static ssize_t nr_resource_show(struct device *dev,
>>>> {
>>>> unsigned long val;
>>>> struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent);
>>>> -
>>>> - val = drvdata->nr_resource;
>>>> + /* @nr_resource represents how many resource selector pairs,
>>>> + * hence multiply by 2.
>>>
>>> Your comment said it correctly, @nr_resource present the number of _pairs_. As
>>> such the code is correct and there is no need to multiply by 2.
>>>
>>
>> Sorry for not mentioned the reason of modified this. From the function
>> @res_ctrl_store, we can see that only one individual resource selector can
>> be accessed via the ->res_idx. Therefore, it may be better to show the
>> number of individual resource selectors.
>
> The end result does not change, i.e this entry represent the number of pairs
> available on the system.
>It's all right. I will keep it no change.

>>
>>>> + */
>>>> + val = 2 * drvdata->nr_resource;
>>>> return scnprintf(buf, PAGE_SIZE, "%#lx\n", val);
>>>> }
>>>> static DEVICE_ATTR_RO(nr_resource);
>>>> @@ -236,7 +238,7 @@ static ssize_t reset_store(struct device *dev,
>>>> }
>>>> config->res_idx = 0x0;
>>>> - for (i = 0; i < drvdata->nr_resource; i++)
>>>> + for (i = 2; i < 2 * drvdata->nr_resource; i++)
>>>> config->res_ctrl[i] = 0x0;
>>>
>>> This hunk is correct - please send a patch for it.
>>
>> Ok.
>>
>>>
>>>> config->ss_idx = 0x0;
>>>> @@ -1663,8 +1665,11 @@ static ssize_t res_idx_store(struct device *dev,
>>>> if (kstrtoul(buf, 16, &val))
>>>> return -EINVAL;
>>>> - /* Resource selector pair 0 is always implemented and reserved */
>>>> - if ((val == 0) || (val >= drvdata->nr_resource))
>>>> + /*
>>>> + * Resource selector pair 0 is always implemented and reserved,
>>>> + * namely an idx with 0 and 1 is illegal.
>>>> + */
>>>> + if ((val == 0) || (val == 1) || (val >= 2 * drvdata->nr_resource))
>>>> return -EINVAL;
>>>
>>> The index, i.e ->res_idx, represent pairs an not individual resource.
>>>
>>> Thanks,
>>> Mathieu
>>>
>>
>> If we want all of the ->res_ctrl accessable, the ->res_idx should represent
>> individual resource. That's the reason.
>
> I see your point now. I think the above condition should be simplified:
>
> if ((val < 2) || (val >= 2 * drvdata->nr_resource))
>
You are right. I will do this.

Thanks.

>>
>> Best regards.
>>
>> Jonathan.
>>
>>>> /*
>>>> --
>>>> 1.9.1
>>>>
>>> .
>>>
> .