linux-kernel - Re: [RFC] [media] imx: assume MEDIA_ENT_F_ATV

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Message-ID: <20170405131725.22c13a1d@vento.lan>
Date:   Wed, 5 Apr 2017 13:17:25 -0300
From:   Mauro Carvalho Chehab <mchehab@...pensource.com>
To:     Devin Heitmueller <dheitmueller@...nellabs.com>
Cc:     Philipp Zabel <p.zabel@...gutronix.de>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Steve Longerbeam <slongerbeam@...il.com>, robh+dt@...nel.org,
        mark.rutland@....com, shawnguo@...nel.org, kernel@...gutronix.de,
        fabio.estevam@....com, Hans Verkuil <hverkuil@...all.nl>,
        nick@...anahar.org, markus.heiser@...marit.de,
        laurent.pinchart+renesas@...asonboard.com, bparrot@...com,
        geert@...ux-m68k.org, Arnd Bergmann <arnd@...db.de>,
        sudipm.mukherjee@...il.com, minghsiu.tsai@...iatek.com,
        tiffany.lin@...iatek.com, jean-christophe.trotin@...com,
        horms+renesas@...ge.net.au, niklas.soderlund+renesas@...natech.se,
        robert.jarzmik@...e.fr, songjun.wu@...rochip.com,
        andrew-ct.chen@...iatek.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        shuah@...nel.org,
        "sakari.ailus@...ux.intel.com" <sakari.ailus@...ux.intel.com>,
        Pavel Machek <pavel@....cz>, devicetree@...r.kernel.org,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        devel@...verdev.osuosl.org,
        Steve Longerbeam <steve_longerbeam@...tor.com>
Subject: Re: [RFC] [media] imx: assume MEDIA_ENT_F_ATV_DECODER entities
 output video on pad 1

Em Wed, 5 Apr 2017 11:39:06 -0400
Devin Heitmueller <dheitmueller@...nellabs.com> escreveu:

> > Currently, the driver doesn't support (2), because, at the time
> > I wrote the driver, I didn't find a way to read the interrupts generated
> > by tvp5150 at em28xx[1], due to the lack of em28xx documentation,
> > but adding support for it shoudn't be hard. I may eventually do it
> > when I have some time to play with my ISEE hardware.  
> 
> For what it's worth, I doubt most of the em28xx designs have the
> tvp5150 interrupt request line connected in any way.

True. But, on embedded hardware, such line may be connected into the
SoC. Actually, from the IGEPv3 expansion diagram:

	https://www.isee.biz/support/downloads/item/igepv2-expansion-rc-schematics

The INT line is connected to CAM_IRQ. That's connected to GPIO_154 pin
at OMAP3.

So, on a first glance, it seems possible to use it, instead of polling.

> You would likely
> have to poll the FIFO status register via I2C,

Yes, I considered this option when I wrote the driver. It could work, 
although it would likely have some performance drawback, as the driver
would need to poll it at least 60 times per second.

> or use the feature to
> embed the sliced data into as VANC data in the 656 output (as
> described in sec 3.9 of the tvp5150am1 spec).

True, but the bridge driver would need to handle such data. 

I remember I looked on this when I wrote the driver, but I was
unable to find a way for em28xx to parse (or forward) such
data packets.

Thanks,
Mauro