linux-kernel - Re: [PATCH] media: venus: assign unique bus

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Message-ID: <aSiGU4Z81Lr0twpj@trex>
Date: Thu, 27 Nov 2025 18:11:47 +0100
From: Jorge Ramirez <jorge.ramirez@....qualcomm.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Cc: Jorge Ramirez <jorge.ramirez@....qualcomm.com>,
        vikash.garodia@....qualcomm.com, dikshita.agarwal@....qualcomm.com,
        bod@...nel.org, mchehab@...nel.org, linux-media@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: venus: assign unique bus_info strings for encoder
 and decoder

On 27/11/25 12:47:19, Konrad Dybcio wrote:
> On 11/25/25 1:55 PM, Jorge Ramirez wrote:
> > On 21/11/25 20:22:13, Konrad Dybcio wrote:
> >> On 11/21/25 7:43 PM, Jorge Ramirez-Ortiz wrote:
> >>> The Venus encoder and decoder video devices currently report the same
> >>> bus_info string ("platform:qcom-venus").
> >>>
> >>> Assign unique bus_info identifiers by appending ":dec" and ":enc" to the
> >>> parent device name. With this change v4l2-ctl will display two separate
> >>> logical devices
> >>>
> >>> Signed-off-by: Jorge Ramirez-Ortiz <jorge.ramirez@....qualcomm.com>
> >>> ---
> >>
> >> Perhaps that's a stupid question, but is there a reason they're
> >> separate at all?
> > 
> > not sure I understand, enc/dec support different APIs, v4l2 controls..is
> > that what you mean?
> 
> Perhaps that shows my lack of knowledge about V4L2. I had imagined that
> a single video device could implement (non-colliding) enc_xyz and dec_xyz
> operations and was wondering why we need two.
>

I think the main issue is that the pipelines have very different
flows/states and semantics so even if the IP block serves both, the
v4l2 abstraction needs to have them separate (plus we want concurrency).