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

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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




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