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Date:   Fri, 8 Oct 2021 15:38:21 +0300
From:   Heikki Krogerus <heikki.krogerus@linux.intel.com>
To:     Bjorn Andersson <bjorn.andersson@linaro.org>
Cc:     Prashant Malani <pmalani@chromium.org>,
        Doug Anderson <dianders@chromium.org>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Rob Clark <robdclark@gmail.com>, Sean Paul <sean@poorly.run>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Abhinav Kumar <abhinavk@codeaurora.org>,
        Stephen Boyd <swboyd@chromium.org>,
        Kuogee Hsieh <khsieh@codeaurora.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        Vara Reddy <varar@codeaurora.org>,
        freedreno <freedreno@lists.freedesktop.org>,
        Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        Benson Leung <bleung@chromium.org>
Subject: Re: [RFC] drm/msm/dp: Allow attaching a drm_panel
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Hi,

On Thu, Oct 07, 2021 at 09:15:12AM -0700, Bjorn Andersson wrote:
> The one thing that I still don't understand though is, if the typec_mux
> is used by the typec controller to inform _the_ mux about the function
> to be used, what's up with the complexity in typec_mux_match()? This is
> what lead me to believe that typec_mux was enabling/disabling individual
> altmodes, rather just flipping the physical switch at the bottom.

Ah, typec_mux_match() is a mess. I'm sorry about that. I think most of
the code in that function is not used by anybody. If I remember
correctly, all that complexity is attempting to solve some
hypothetical corner case(s). Probable a case where we have multiple
muxes per port to deal with.

I think it would probable be best to clean the function to the bare
minimum by keeping only the parts that are actually used today
(attached).

thanks,

-- 
heikki

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diff --git a/drivers/usb/typec/mux.c b/drivers/usb/typec/mux.c
index c8340de0ed495..44f168c9bd9bf 100644
--- a/drivers/usb/typec/mux.c
+++ b/drivers/usb/typec/mux.c
@@ -193,56 +193,15 @@ static int mux_fwnode_match(struct device *dev, const void *fwnode)
 static void *typec_mux_match(struct fwnode_handle *fwnode, const char *id,
 			     void *data)
 {
-	const struct typec_altmode_desc *desc = data;
 	struct device *dev;
-	bool match;
-	int nval;
-	u16 *val;
-	int ret;
-	int i;
 
 	/*
-	 * Check has the identifier already been "consumed". If it
-	 * has, no need to do any extra connection identification.
+	 * The connection identifier will be needed with device graph (OF graph).
+	 * Device graph is not supported by this code yet, so bailing out.
 	 */
-	match = !id;
-	if (match)
-		goto find_mux;
-
-	/* Accessory Mode muxes */
-	if (!desc) {
-		match = fwnode_property_present(fwnode, "accessory");
-		if (match)
-			goto find_mux;
-		return NULL;
-	}
-
-	/* Alternate Mode muxes */
-	nval = fwnode_property_count_u16(fwnode, "svid");
-	if (nval <= 0)
-		return NULL;
-
-	val = kcalloc(nval, sizeof(*val), GFP_KERNEL);
-	if (!val)
-		return ERR_PTR(-ENOMEM);
-
-	ret = fwnode_property_read_u16_array(fwnode, "svid", val, nval);
-	if (ret < 0) {
-		kfree(val);
-		return ERR_PTR(ret);
-	}
-
-	for (i = 0; i < nval; i++) {
-		match = val[i] == desc->svid;
-		if (match) {
-			kfree(val);
-			goto find_mux;
-		}
-	}
-	kfree(val);
-	return NULL;
+	if (id)
+		return ERR_PTR(-ENOTSUPP);
 
-find_mux:
 	dev = class_find_device(&typec_mux_class, NULL, fwnode,
 				mux_fwnode_match);
 

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