linux-kernel - Re: [PATCH v3 2/3] drm: Add API for capturing frame CRCs

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Date:	Mon, 8 Aug 2016 11:09:52 +0200
From:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
To:	Daniel Stone <daniel@...ishbar.org>
Cc:	Jonathan Corbet <corbet@....net>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	Daniel Vetter <daniel.vetter@...el.com>,
	Emil Velikov <emil.velikov@...labora.com>
Subject: Re: [PATCH v3 2/3] drm: Add API for capturing frame CRCs

On 6 August 2016 at 19:04, Daniel Stone <daniel@...ishbar.org> wrote:
> Hi Tomeu,
>
> On 22 July 2016 at 15:10, Tomeu Vizoso <tomeu.vizoso@...labora.com> wrote:
>> +/**
>> + * DOC: CRC ABI
>> + *
>> + * DRM device drivers can provide to userspace CRC information of each frame as
>> + * it reached a given hardware component (a "source").
>> + *
>> + * Userspace can control generation of CRCs in a given CRTC by writing to the
>
> s/can/must/
>
> Is it worth having 'auto' as a default source perhaps?

Yup, it's the case in v4, so you just cat the data file and start getting CRCs.

>> + * file dri/0/crtc-N/crc/control in debugfs, with N being the index of the CRTC.
>> + * Accepted values are source names (which are driver-specific) and the "none"
>> + * and "auto" keywords. "none" will disable CRC generation and "auto" will let
>> + * the driver select a default source of frame CRCs for this CRTC.
>
> Is it also worth having 'connector-%s' (named as per sysfs, e.g.
> connector-HDMI-A-0) as a standardised entry, for cloneable CRTCs which
> have CRC control on the connector rather than the CRTC?

My impression right now is that only "auto" makes sense as a
standardised entry, as any explicit sources are pretty much
hw-dependent so the tests will need knowledge about the hw anyway.

The IGT tests already try each connector in each CRTC when looking for
a setup that supports CRC capture (with the auto source).

Regards,

Tomeu