linux-kernel - Re: [PATCH v3 17/29] media: iris: implement query_cap, query_ctrl and query

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Message-ID: <a4f01eaa-bfb2-a5a4-87b2-2960aa61d29e@quicinc.com>
Date: Thu, 26 Sep 2024 16:20:47 +0530
From: Dikshita Agarwal <quic_dikshita@...cinc.com>
To: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Vikash Garodia
	<quic_vgarodia@...cinc.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        "Mauro Carvalho Chehab" <mchehab@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>
CC: <linux-media@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Vedang Nagar
	<quic_vnagar@...cinc.com>
Subject: Re: [PATCH v3 17/29] media: iris: implement query_cap, query_ctrl and
 query_menu ioctls



On 9/24/2024 8:19 PM, Bryan O'Donoghue wrote:
> On 27/08/2024 11:05, Dikshita Agarwal via B4 Relay wrote:
>> From: Vedang Nagar <quic_vnagar@...cinc.com>
>>
>> Implement query_cap, query_ctrl and query_menu ioctls in the
>> driver with necessary hooks.
>>
>> Signed-off-by: Vedang Nagar <quic_vnagar@...cinc.com>
>> Signed-off-by: Dikshita Agarwal <quic_dikshita@...cinc.com>
>> ---
>>   drivers/media/platform/qcom/iris/iris_vidc.c | 89
>> ++++++++++++++++++++++++++++
>>   1 file changed, 89 insertions(+)
>>
>> diff --git a/drivers/media/platform/qcom/iris/iris_vidc.c
>> b/drivers/media/platform/qcom/iris/iris_vidc.c
>> index 7d5da30cb1d1..1dd612b7cec5 100644
>> --- a/drivers/media/platform/qcom/iris/iris_vidc.c
>> +++ b/drivers/media/platform/qcom/iris/iris_vidc.c
>> @@ -362,6 +362,92 @@ static int iris_enum_framesizes(struct file *filp,
>> void *fh,
>>       return ret;
>>   }
>>   +static int iris_querycap(struct file *filp, void *fh, struct
>> v4l2_capability *cap)
>> +{
>> +    struct iris_inst *inst;
>> +    int ret = 0;
>> +
>> +    inst = iris_get_inst(filp, fh);
>> +    if (!inst)
>> +        return -EINVAL;
>> +
>> +    mutex_lock(&inst->lock);
>> +    strscpy(cap->driver, IRIS_DRV_NAME, sizeof(cap->driver));
>> +    strscpy(cap->bus_info, IRIS_BUS_NAME, sizeof(cap->bus_info));
>> +    memset(cap->reserved, 0, sizeof(cap->reserved));
>> +    strscpy(cap->card, "iris_decoder", sizeof(cap->card));
>> +    mutex_unlock(&inst->lock);
> 
> Locking is a good thing but, this seems very rote.
> 
> What's being protected here ?
> 
> Please take a critical - no pun intended - look at your locking strategy here.
> 
> I mentioned previously taking a core lock and releasing it with a level of
> granularity that didn't make a ton of sense to me, here's another example
> of locking for locking's sake.
> 
> Please go through your code, look at your locks with a critical eye and say
> "what's this for, why are doing this, what is the lock supposed to
> guarantee here".
> 
> I appreciate that can be difficult with a progressive patchset so recommend
> jumping in at the end and doing that analysis.
> 
sure, will revisit the usage of inst->lock and improve as needed.
> ---
> bod