linux-kernel - Re: [PATCH] media input infrastructure:tw686x...

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Message-ID: <cdc0c943-f5be-f970-ff51-1cd14f605b01@xs4all.nl>
Date:   Sat, 3 Aug 2019 09:24:59 -0300
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Mark Balantzyan <mbalant3@...il.com>
Cc:     ezequiel@...guardiasur.com.ar, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media input infrastructure:tw686x...

Hi Mark,

On 7/31/19 6:32 PM, Mark Balantzyan wrote:
> Hi Hans, all,
> 
> Sorry for the poor patching, I am a student and as you may tell still 
> new to this system. At the time of the patching, I wasn't fully informed 
> of all the requirements that go into such things, and am still learning.
> 
> Would it be alright if I submit a report instead? In order to, I am 
> (still, sorry) trying to understand the issue at hand. How in fact may 
> the release() callback be overridden (by a tw686x-specific function) to 
> free the dma memory and call video_device_release()? To my understanding 
> at the time, this was merely a re-implementation of video_device_release 
> with said requirements and subtraction of extra features from 
> tw686x_video_free()..

Sorry, you'll need to discuss this with your mentor. I really don't have 
time to look at reports or anything like that. I'm a media subsystem 
maintainer, not your mentor. And I expect that you spend time trying to 
understand the code by looking at how other drivers do this and look at 
kernel documentation like this:

https://linuxtv.org/downloads/v4l-dvb-apis-new/media_kapi.html

Regards,

	Hans

> 
>      This release() callback is called by the V4L2 framework when the 
> last user
>      of the device closes its filehandle, so that's a good point to free 
> all
>      the memory. Doing it earlier (as the current code does) runs the 
> risk that someone might
>      still access that memory, and you don't want that.
> 
> Yes, I definitely don't want that. :)
> 
> Thank you,
> Mark
>