linux-kernel - Re: [PATCH v3 15/15] media: qcom: camss: Comment CSID dt

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Message-ID: <b4545982-af6c-5460-d662-36b0eb80bb4e@linaro.org>
Date:   Mon, 28 Aug 2023 16:34:42 +0100
From:   Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>, rfoss@...nel.org,
        todor.too@...il.com, agross@...nel.org, andersson@...nel.org,
        mchehab@...nel.org, hverkuil-cisco@...all.nl,
        laurent.pinchart@...asonboard.com, sakari.ailus@...ux.intel.com,
        andrey.konovalov@...aro.org
Cc:     linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 15/15] media: qcom: camss: Comment CSID dt_id field

On 26/08/2023 11:18, Konrad Dybcio wrote:
>> +		/*
>> +		 * A value caled 'CID' gets generated internal to CAMSS logic
>> +		 * which is a concatenation of [vc:6 | dt_id:2] hence we reuse
>> +		 * the least significant two bits of the VC to 'stuff' the CID value.
>> +		 */
>>   		u8 dt_id = vc;
> And where are you discarding the non-2-lsb?

At the assignment of dt_id

vc:6
dt_id:2

=>

cid:8 = [vc:6 | dt_id:2]
vc == 00110110
cid = [110110 | 10]

I have no more information what CID is or how the bitfield is populated 
than I have already indicated in the comment/commit log.

---
bod