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

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Message-ID: <35d86818-8b50-1c0e-40a0-5f80c4b24a32@oss.qualcomm.com>
Date: Tue, 25 Nov 2025 18:39:14 +0530
From: Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>
To: Jorge Ramirez <jorge.ramirez@....qualcomm.com>,
        Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>
Cc: vikash.garodia@....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 11/25/2025 6:22 PM, Jorge Ramirez wrote:
> On 25/11/25 13:59:56, Dikshita Agarwal wrote:
>>
>>
>> On 11/22/2025 12:13 AM, 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>
>>> ---
>>>  drivers/media/platform/qcom/venus/vdec.c | 5 +++++
>>>  drivers/media/platform/qcom/venus/venc.c | 5 +++++
>>>  2 files changed, 10 insertions(+)
>>>
>>> diff --git a/drivers/media/platform/qcom/venus/vdec.c b/drivers/media/platform/qcom/venus/vdec.c
>>> index 4a6641fdffcf..63f6ae1ff6ac 100644
>>> --- a/drivers/media/platform/qcom/venus/vdec.c
>>> +++ b/drivers/media/platform/qcom/venus/vdec.c
>>> @@ -433,9 +433,14 @@ vdec_g_selection(struct file *file, void *fh, struct v4l2_selection *s)
>>>  static int
>>>  vdec_querycap(struct file *file, void *fh, struct v4l2_capability *cap)
>>>  {
>>> +	struct venus_inst *inst = to_inst(file);
>>> +	struct venus_core *core = inst->core;
>>> +
>>>  	strscpy(cap->driver, "qcom-venus", sizeof(cap->driver));
>>>  	strscpy(cap->card, "Qualcomm Venus video decoder", sizeof(cap->card));
>>>  	strscpy(cap->bus_info, "platform:qcom-venus", sizeof(cap->bus_info));
>>> +	snprintf(cap->bus_info, sizeof(cap->bus_info),
>>> +		 "platform:%s:dec", dev_name(core->dev));
>>
>> Is there a reason to keep both strscpy() and snprintf() for cap->bus_info?
>> The second call to snprintf() seems to overwrite the value set by
>> strscpy(), making the first assignment redundant. Would it be cleaner to
>> remove the strscpy() line and rely solely on snprintf()?
> 
> argh, my bad, you are right. will fix.
> 
> perhaps we should just have instead
> 
> decoder:
> strscpy(cap->bus_info,"platform:qcom-venus-dec", sizeof(cap->bus_info));
> 
> encoder:
> strscpy(cap->bus_info, "platform:qcom-venus-enc",sizeof(cap->bus_info)); on the encoder
> 
> I suppose the additional info provided by the dev_name is not really
> important to consumers.

In-fact, we don't even need to fill the bus_info, received a similar
comment on iris [1]
[1]:
https://lore.kernel.org/linux-media/c4350128-a05c-47af-a7e7-2810171cd311@xs4all.nl/


Thanks,
Dikshita
> 
> ?
>