linux-kernel - Re: [linux-sunxi] Re: [PATCH v2 14/27] drm/sun4i: Don't check for panel or bridge on TV TCONs

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Date:   Wed, 13 Jun 2018 18:20:07 +0200
From:   Jernej Škrabec <jernej.skrabec@...l.net>
To:     linux-sunxi@...glegroups.com, wens@...e.org
Cc:     Maxime Ripard <maxime.ripard@...tlin.com>,
        Rob Herring <robh+dt@...nel.org>,
        David Airlie <airlied@...ux.ie>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Sean Paul <seanpaul@...omium.org>,
        Mark Rutland <mark.rutland@....com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>
Subject: Re: [linux-sunxi] Re: [PATCH v2 14/27] drm/sun4i: Don't check for panel or bridge on TV TCONs

Dne sreda, 13. junij 2018 ob 10:04:20 CEST je Chen-Yu Tsai napisal(a):
> On Wed, Jun 13, 2018 at 3:46 PM, Maxime Ripard
> 
> <maxime.ripard@...tlin.com> wrote:
> > On Tue, Jun 12, 2018 at 10:00:23PM +0200, Jernej Skrabec wrote:
> >> TV TCONs are always connected to TV or HDMI encoder, so it doesn't make
> >> sense to check if panel or bridge is connected to them.
> >> 
> >> Check if TCON has channel 0 and only then check for connected panel or
> >> bridges.
> >> 
> >> Signed-off-by: Jernej Skrabec <jernej.skrabec@...l.net>
> >> ---
> >> 
> >>  drivers/gpu/drm/sun4i/sun4i_tcon.c | 12 +++++++++---
> >>  1 file changed, 9 insertions(+), 3 deletions(-)
> >> 
> >> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> >> b/drivers/gpu/drm/sun4i/sun4i_tcon.c index b1205a7bc20f..c9ffa5381185
> >> 100644
> >> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> >> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> >> @@ -1189,13 +1189,19 @@ static const struct component_ops sun4i_tcon_ops
> >> = {>> 
> >>  static int sun4i_tcon_probe(struct platform_device *pdev)
> >>  {
> >>  
> >>       struct device_node *node = pdev->dev.of_node;
> >> 
> >> +     const struct sun4i_tcon_quirks *quirks;
> >> 
> >>       struct drm_bridge *bridge;
> >>       struct drm_panel *panel;
> >>       int ret;
> >> 
> >> -     ret = drm_of_find_panel_or_bridge(node, 1, 0, &panel, &bridge);
> >> -     if (ret == -EPROBE_DEFER)
> >> -             return ret;
> >> +     quirks = of_device_get_match_data(&pdev->dev);
> > 
> > We should probably check ofr the pointer value before dereferencing it.
> 
> I think we've discussed this before. If the driver has data structures
> for all the supported compatible strings, and it is device tree only,
> then we should just let it blow up in the user's face, since they are
> obviously doing something they shouldn't be doing to get the driver
> to probe without a compatible string match.

TCON can't work with no quirks specified, since that would mean that neither 
channels are present. Additionally, sun4i_tcon_bind() also doesn't check if 
quirks are NULL or not. So I concur with Chen-Yu here.

Best regards,
Jernej