linux-kernel - Re: [RESEND PATCH v6 17/17] media: qcom: camss: Comment CSID dt

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Message-ID: <314cee42-c235-4d2a-b4a6-4da92d2c1548@xs4all.nl>
Date:   Wed, 27 Sep 2023 14:05:03 +0200
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-media@...r.kernel.org,
        laurent.pinchart@...asonboard.com, rfoss@...nel.org,
        todor.too@...il.com, agross@...nel.org, andersson@...nel.org,
        konrad.dybcio@...aro.org, mchehab@...nel.org,
        sakari.ailus@...ux.intel.com, andrey.konovalov@...aro.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH v6 17/17] media: qcom: camss: Comment CSID dt_id
 field

On 27/09/2023 14:03, Bryan O'Donoghue wrote:
> On 27/09/2023 12:42, Hans Verkuil wrote:
>>> +        /*
>>> +         * DT_ID is a two bit bitfield that is concatenated with
>>> +         * the four least significant bits of the six bit VC
>>> +         * bitfield to generate an internal CID value.
>>> +         *
>>> +         * CSID_RDI_CFG0(vc)
>>> +         * DT_ID : 28:27
>>> +         * VC    : 26:22
>> This is 5 bits, not 6 bits as the comment above says. Which is right?
> 
> Yes you're right I had "DT" which is six bits in my head when I wrote this. The VC bitfield is five.
> 
>>
>>> +         * DT    : 21:16
>>> +         *
>>> +         * CID   : VC 3:0 << 2 | DT_ID 1:0
>>> +         */
>>>           u8 dt_id = vc;
>> So if dt_id is 2 bits, and vc can be more than 2 bits in the future,
>> shouldn't this read "vc & 3"?
> 
> Hmm...
> 
> val |= dt_id << RDI_CFG0_DT_ID;
> 
> yes that would overrun otherwise.

No need to repost the whole series, just post a v6.1 for this patch only.

Regards,

	Hans