linux-kernel - Re: [PATCH v3 2/2] media: platform: Add Aspeed Video Engine driver

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Message-Id: <ca4757b9-0825-bbbf-b388-0295fd13bad7@linux.vnet.ibm.com>
Date:   Wed, 3 Oct 2018 15:43:08 -0500
From:   Eddie James <eajames@...ux.vnet.ibm.com>
To:     Hans Verkuil <hverkuil@...all.nl>,
        Eddie James <eajames@...ux.ibm.com>,
        linux-kernel@...r.kernel.org
Cc:     mark.rutland@....com, devicetree@...r.kernel.org,
        linux-aspeed@...ts.ozlabs.org, andrew@...id.au,
        openbmc@...ts.ozlabs.org, robh+dt@...nel.org, mchehab@...nel.org,
        linux-media@...r.kernel.org
Subject: Re: [PATCH v3 2/2] media: platform: Add Aspeed Video Engine driver



On 09/28/2018 06:30 AM, Hans Verkuil wrote:
> On 09/25/2018 09:27 PM, Eddie James wrote:
>> The Video Engine (VE) embedded in the Aspeed AST2400 and AST2500 SOCs
>> can capture and compress video data from digital or analog sources. With
>> the Aspeed chip acting a service processor, the Video Engine can capture
>> the host processor graphics output.
>>
>> Add a V4L2 driver to capture video data and compress it to JPEG images.
>> Make the video frames available through the V4L2 streaming interface.
>>
>> Signed-off-by: Eddie James <eajames@...ux.ibm.com>

>> +	}
>> +
>> +	video->height = (bottom - top) + 1;
>> +	video->width = (right - left) + 1;
>> +	size = video->height * video->width;
> It looks like you can actually determine the blanking width/height and
> possibly even more detailed information that would be very useful to
> show with the DV_TIMINGS ioctls.

Hmm. This information is related to the video signal captured from the 
host. That information has nothing to do with the buffer that is 
compressed and grabbed by the driver and ultimately provided to 
userspace. Isn't the timing information meaningless for JPEG frames?

Forgot to include this question in my previous reply, sorry for the 
additional mail.

Thanks,
Eddie

>
>> +
>> +	/* Don't use direct mode below 1024 x 768 (irqs don't fire) */
>> +	if (size < DIRECT_FETCH_THRESHOLD) {
>> +		aspeed_video_write(video, VE_TGS_0,
>> +				   FIELD_PREP(VE_TGS_FIRST, left - 1) |
>> +				   FIELD_PREP(VE_TGS_LAST, right));
>> +		aspeed_video_write(video, VE_TGS_1,
>> +				   FIELD_PREP(VE_TGS_FIRST, top) |
>>