[PATCH 3/5] drm/i2c: tda998x: add support for writing SPD

[Brian Starkey]

On Wed, Jan 30, 2019 at 05:23:40PM +0000, Russell King - ARM Linux admin wrote:
> On Wed, Jan 30, 2019 at 03:41:04PM +0000, Brian Starkey wrote:
> > Hi Russell,
> > 
> > These did eventually reach me on Saturday evening.
> > 
> > On Fri, Jan 25, 2019 at 09:43:19AM +0000, Russell King wrote:
> > > Add support for writing the SPD infoframe to the TDA998x.  Identify us
> > > as "Generic" vendor "PC" product, and as "PC general" source device
> > > information.
> > > 
> > > Signed-off-by: Russell King <rmk+kernel at armlinux.org.uk>
> > > ---
> > 
> > As this infoframe is optional, and is intended to provide a "useful"
> > name to the user, I wonder if there's really much value in just
> > sending "Generic"/"PC"? It seems that it might be better to just not
> > send the SPD infoframe until we have a way to put something more
> > useful there (e.g. specified by the host driver).
> 
> It's along the lines of what other drivers do - are you suggesting
> that other drivers should not send the SPD infoframe either?
> 
> E.g.
> 
> static void vc4_hdmi_set_spd_infoframe(struct drm_encoder *encoder)
> {
>         union hdmi_infoframe frame;
>         int ret;
> 
>         ret = hdmi_spd_infoframe_init(&frame.spd, "Broadcom", "Videocore");
> ===
>         mtk_hdmi_setup_spd_infoframe(hdmi, "mediatek", "On-chip HDMI");
> ===
>         ret = hdmi_spd_infoframe_init(&frame.spd, "Intel", "Integrated gfx");
> 
> None of these convey a "useful" name to the user, unless the user
> knows what is inside their device - eg, "it's a mediatek SoC" or
> "it's a Broadcom SoC".

I grepped the same, but I came to a different conclusion. From
"Broadcom", "mediatek" and "Intel" I can identify a device, if I know
it contains one of those components. From "Generic"/"PC" I can't tell
anything at all.

> 
> I could send instead "Philips" "TDA998x" which would be on-par with
> these strings.
> 

I don't agree that it would be "on-par", but IMO it would be an
improvement over "Generic"/"PC". The strings above describe the "host"
driver/device, rather than the transmitter per-se. I think it's fair
to say a user is more likely to know what SoC their device contains
than which HDMI transmitter is connected to that SoC.

> Maybe there should be a way to set these from DT and/or userspace?

DT is a nice idea. Maybe Product from /model and Vendor from
/compatible (though how you turn a DT compatible into a human-readable
vendor could be fun).

That sounds like something which shouldn't be local to tda998x,
though.

Thanks,
-Brian

> 
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