linux-kernel - Re: [PATCH v8 1/3] media: qcom: camss: Add common TPG support

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Message-ID: <c3a56645-0399-447c-b7a5-d7af9f567a7d@linaro.org>
Date: Fri, 16 Jan 2026 11:24:50 +0200
From: Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>
To: Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
 Wenmeng Liu <wenmeng.liu@....qualcomm.com>, Robert Foss <rfoss@...nel.org>,
 Todor Tomov <todor.too@...il.com>, Mauro Carvalho Chehab <mchehab@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
 linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v8 1/3] media: qcom: camss: Add common TPG support

On 1/15/26 17:54, Bryan O'Donoghue wrote:
> On 15/01/2026 02:58, Vladimir Zapolskiy wrote:
>>>> Writing proper values to registers should be a concern on the driver
>>>> level,
>>>> it sounds improper to push this simple task and responsibility to
>>>> userspace.
>>>
>>> I think we should stick to the same format as is already upstream for
>>> the CSID version of this - which is the same data.
>>>
>>
>> It is not the same and it will not be the same, if the currently presented
>> version is taken. If TPG modes in CSID are continuous, here they are not,
>> so it makes a big difference for userspace, and better it should be
>> removed.
> 
> Not sure I follow you here.
> 
> The set of strings for camss-csid we have now is:
> 
> const char * const csid_testgen_modes[] = {
>           "Disabled",
>           "Incrementing",
>           "Alternating 0x55/0xAA",
>           "All Zeros 0x00",
>           "All Ones 0xFF",
>           "Pseudo-random Data",
>           "User Specified",
>           "Complex pattern",
>           "Color box",
>           "Color bars",
>           NULL
> };
> 
> Wengmeng has
> 
> +const char * const testgen_payload_modes[] = {
> +	"Disabled",
> +	"Incrementing",
> +	"Alternating 0x55/0xAA",
> +	"Reserved",
> +	"Reserved",
> +	"Pseudo-random Data",
> +	"User Specified",
> +	"Reserved",
> +	"Reserved",
> +	"Color bars",
> +	"Reserved"
> +};
> 
> I think the "Reserved" should go away but, other than that we should

That's what I've asked, there is no dispute.

> keep namespace consistency between CSID-TPG and standalone-TPG.
> 

When "consistency" is not defined, it's just a fine sounding buzzword.

CSID TPG has:
* modes, which numbers are continuously incremented,
* the number of TPG modes for a user is expectedly the number of TPG modes.

The displayed v8 of the "standalone TPG" broke both assumptions from above,
so there is no more "consistency" between two TPGs, while I explicitly ask
to preserve the "consistency".

-- 
Best wishes,
Vladimir