linux-kernel - Re: [PATCH v2 5/9] coresight: Dynamically add connections

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Message-ID: <d55db287-52ca-1e25-6275-73c5bbee6e54@arm.com>
Date:   Wed, 29 Mar 2023 13:02:31 +0100
From:   James Clark <james.clark@....com>
To:     Suzuki K Poulose <suzuki.poulose@....com>,
        coresight@...ts.linaro.org
Cc:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/9] coresight: Dynamically add connections



On 16/03/2023 17:12, Suzuki K Poulose wrote:
> On 10/03/2023 16:06, James Clark wrote:
>> Add a function for adding connections dynamically. This also removes
>> the 1:1 mapping between port number and the index into the connections
>> array. The only place this mapping was used was in the warning for
>> duplicate output ports, which has been replaced by a search. Other
>> uses of the port number already use the port member variable.
>>
>> Being able to dynamically add connections will allow other devices like
>> CTI to re-use the connection mechanism despite not having explicit
>> connections described in the DT.
>>
>> Signed-off-by: James Clark <james.clark@....com>
>> ---
>>   .../hwtracing/coresight/coresight-platform.c  | 77 ++++++++++++++-----
>>   include/linux/coresight.h                     |  7 +-
>>   2 files changed, 64 insertions(+), 20 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-platform.c
>> b/drivers/hwtracing/coresight/coresight-platform.c
>> index c77238cdf448..16553f7dde12 100644
>> --- a/drivers/hwtracing/coresight/coresight-platform.c
>> +++ b/drivers/hwtracing/coresight/coresight-platform.c
>> @@ -27,8 +27,9 @@ static int coresight_alloc_conns(struct device *dev,
>>                    struct coresight_platform_data *pdata)
>>   {
>>       if (pdata->nr_outconns) {
>> -        pdata->out_conns = devm_kcalloc(dev, pdata->nr_outconns,
>> -                        sizeof(*pdata->out_conns), GFP_KERNEL);
>> +        pdata->out_conns = devm_krealloc_array(
>> +            dev, pdata->out_conns, pdata->nr_outconns,
> 
> super minor nit:
>         pdata->out_conns = devm_krealloc_array(dev,
> 

This is actually clang-format's doing when using the kernel rules in the
root of the repo. I started using it because of some other style
comments I got before. Not sure if this time it's just done something
bad or it's technically ok.

I formatted everything in V3 with it so it should at least all be
consistent.

>        
>> +            sizeof(*pdata->out_conns), GFP_KERNEL | __GFP_ZERO);
>>           if (!pdata->out_conns)
>>               return -ENOMEM;
>>       }
>> @@ -36,6 +37,48 @@ static int coresight_alloc_conns(struct device *dev,
>>       return 0;
>>   }
>>   +/*
>> + * Add a connection in the first free slot, or realloc
>> + * if there is no space. @conn's contents is copied into the new slot.
>> + *
>> + * If the output port is already assigned on this device, return -EINVAL
>> + */
>> +int coresight_add_conn(struct device *dev,
>> +               struct coresight_platform_data *pdata,
>> +               const struct coresight_connection *conn)
>> +{
>> +    int ret;
>> +    struct coresight_connection *free_conn = NULL;
>> +    struct coresight_connection *i;
>> +
>> +    /*
>> +     * Search for a free slot, and while looking for one, warn
>> +     * on any existing duplicate output port.
>> +     */
>> +    for (i = pdata->out_conns; i < pdata->out_conns +
>> pdata->nr_outconns;
>> +         ++i) {
> 
> minor nit: I see why you have gone against using "i" as index into
> the array. But I think having that as the index is still better
> readable.
>     for (i = 0; i < pdata->nr_outconns; i++) {
>         struct coresight_connection *c = &pdata->out_conns[i];
> >> +        if (i->remote_fwnode && conn->port != -1 &&
>> +            i->port == conn->port) {
>> +            dev_warn(dev, "Duplicate output port %d\n", i->port);
>> +            return -EINVAL;
>> +        }
>> +        if (!i->remote_fwnode && !free_conn)
>> +            free_conn = i;
>> +    }
>> +
>> +    if (!free_conn) {
> 
> and:
>     /* No free slots */
>     if (i == pdata->nr_outconns) {
> 
>> +        pdata->nr_outconns++;
>> +        ret = coresight_alloc_conns(dev, pdata);
>> +        if (ret)
>> +            return ret;
>> +        free_conn = &pdata->out_conns[pdata->nr_outconns - 1];
>> +    }
>> +
> 
> and:
>     pdata->out_conns[i] = *conn;
> 
> > Otherwise looks good to me.
> 
> Suzuki
> 
>