Re: [PATCH v3 17/29] media: iris: implement query_cap, query_ctrl and query_menu ioctls

[Bryan O'Donoghue]

On 27/08/2024 11:05, Dikshita Agarwal via B4 Relay wrote:
> From: Vedang Nagar <quic_vnagar@xxxxxxxxxxx>
>
> Implement query_cap, query_ctrl and query_menu ioctls in the
> driver with necessary hooks.
>
> Signed-off-by: Vedang Nagar <quic_vnagar@xxxxxxxxxxx>
> Signed-off-by: Dikshita Agarwal <quic_dikshita@xxxxxxxxxxx>
> ---
>   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.

---
bod