linux-kernel - Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver

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Message-ID: <15a879b3-8fb9-6821-3cdc-104ba583ac12@gmail.com>
Date:   Wed, 8 Apr 2020 01:08:27 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.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 v6 6/9] media: tegra: Add Tegra210 Video input driver

08.04.2020 00:08, Sowjanya Komatineni пишет:
...
>>> I think you need a semaphore with resource count = 2.
>> we hold on to issuing capture if more than 2 buffers are queued and it
>> continues only after fifo has min 1 slot empty
> 
> 
> Just want to close on this part of feedback. Hope above explanation is
> clear regarding triggering/issuing at max 2 frame capture to VI HW and
> also regarding capture threads where they use wait_event_interruptible
> to prevent blocking waiting for buffers to be available for captures.
> 
> So no changes related to this part are needed in v7.
>From what I see in the code, you "hold on" by making kthread to spin in
a busy-loop while caps_inflight >= SYNCPT_FIFO_DEPTH. So some change
should be needed to prevent this.

The wait_event_interruptible seems should be okay.