linux-kernel - Re: [PATCH 1/9] media: qcom: camss: Add per sub-device type resources

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Message-ID: <b852d178-dfb6-47fb-a5bf-55b614cbfae3@quicinc.com>
Date: Tue, 12 Mar 2024 17:01:53 +0200
From: "Gjorgji Rosikopulos (Consultant)" <quic_grosikop@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@...aro.org>, <rfoss@...nel.org>,
        <todor.too@...il.com>, <bryan.odonoghue@...aro.org>,
        <andersson@...nel.org>, <mchehab@...nel.org>
CC: <linux-media@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <laurent.pinchart@...asonboard.com>,
        <hverkuil-cisco@...all.nl>, <quic_hariramp@...cinc.com>
Subject: Re: [PATCH 1/9] media: qcom: camss: Add per sub-device type resources

Hi Konrad,

Thank you for the review.

On 3/12/2024 4:44 PM, Konrad Dybcio wrote:
> 
> 
> On 2/27/24 13:24, Gjorgji Rosikopulos wrote:
>> From: Radoslav Tsvetkov <quic_rtsvetko@...cinc.com>
>>
>> Currently resources structure grows with additional parameters
>> required for
>> each sub-deivce. However each sub-device has some specific resources or
>> configurations which need to be passed during the initialization.
>>
>> This change adds per sub-device type structure to simplify the things
>> and removes the magical void pointer to hw_ops.
> 
> I'm not quite sure what the benefit here is, as opposed to simply
> extending <name>_device?
> 
> Generally, I think the driver state as of today is somewhat backwards..
> 
> We define a common set of resources, and then assign them subdev-specific
> ops, instead of defining the subdev and consuming clocks/pds/resets
> within a subdevice there..

In the current code only ops are specific. However there are other
configurations passed to the sub-devices which are actually specific to
different sub-device, as an example:

1. is_lite flag. The lite flag is valid for csid and vfe but not for csiphy.

2. line_num this is valid only for vfe sub-device.

3. video device available formats. Those formats are only used by the
vfe sub-device and are not valid to other sub-devices which are not
having any video device connected, (those will be added in next patches
in the patch-set).

Please check the other changes in this patch-set maybe it will make more
sense.

I am not sure with such differences in the sub-device code we can have
generic structure which contains only ops...

And please note that when we are introducing new sub-device for other
SoC it may need additional specific configuration.

Regards,

~Gjorgji