linux-kernel - Re: [RFC PATCH v11 6/9] media: tegra: Add Tegra210 Video input driver

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Message-ID: <9b2b36ad-82cb-bcf6-24d6-3533b51918c8@nvidia.com>
Date:   Thu, 30 Apr 2020 12:51:35 -0700
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <frankc@...dia.com>, <hverkuil@...all.nl>,
        <sakari.ailus@....fi>, <helen.koike@...labora.com>
CC:     <sboyd@...nel.org>, <linux-media@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-clk@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v11 6/9] media: tegra: Add Tegra210 Video input driver


On 4/30/20 12:47 PM, Dmitry Osipenko wrote:
> 30.04.2020 22:32, Sowjanya Komatineni пишет:
>> On 4/30/20 6:38 AM, Dmitry Osipenko wrote:
>>> 30.04.2020 01:00, Sowjanya Komatineni пишет:
>>>> +/**
>>>> + * struct tegra_csi_ops - Tegra CSI operations
>>>> + *
>>>> + * @csi_streaming: programs csi hardware to enable or disable
>>>> streaming.
>>>> + * @csi_err_recover: csi hardware block recovery in case of any
>>>> capture errors
>>>> + *        due to missing source stream or due to improper csi input
>>>> from
>>>> + *        the external source.
>>>> + */
>>>> +struct tegra_csi_ops {
>>>> +    int (*csi_streaming)(struct tegra_csi_channel *csi_chan, u8
>>>> pg_mode,
>>>> +                 int enable);
>>> What about to split csi_streaming() into csi_start_streaming() /
>>> csi_stop_streaming()?
>>>
>>> This will make tegra_csi_ops to be consistent with the tegra_ve_ops. A
>>> separated start/stop operations are somewhat more natural to have in
>>> general.
>> vi ops is for vb2_ops which has separate start/stop so has seperate
>> start/stop for vi ops.
>>
>> csi is subdev and csi ops is for v4l2_subdev_ops which as s_stream
>> callback only.
>>
>> So, created single stream function for csi to match same as subdev_ops.
> It will be nicer to have separate ops for CSI, regardless of the
> subdev_ops. It should be okay to have a single-combined ops if CSI
> start/stop was trivial, but it's not the case here.
>
> For example, the pm_runtime_put() shouldn't be invoked if stream's
> stopping fails. The stopping can't fail for the current code, but this
> could change in the future.
>
> You could make csi_streaming to return void, telling explicitly that
> this code can't fail. Then the combined OPS should be okay to have.

we don't return anything for stop stream. OK can make it split to 
explicitly specify no return code during stop stream.

will split this in v12