Re: [PATCH] usb: typec: mux: Fix typec_switch_match()

[Marek Vasut]

On 8/18/26 6:24 PM, Sebastian Reichel wrote:

Hello Sebastian,

> On Mon, Aug 17, 2026 at 08:22:39PM +0200, Marek Vasut wrote:
> > The fwnode_typec_switch_get() sporadically returns NULL instead of an
> > -EPROBE_DEFER for orientation-switch described in DT. This makes it
> > impossible to discern whether the DT does describe an orientation-switch
> > which did not probe yet, or whether the DT does not describe the switch.
> > This happens with gpio-sbu-mux connected to an I2C GPIO expander.
> >
> > The class_find_device() on typec_switch_match() may return NULL in case
> > the mux did not probe just yet early on boot. The sw_devs[] array can be
> > empty on boot as well. If these two conditions occur, then the conditional
> > if (to_typec_switch_dev(dev) == sw_devs[i]) evaluates to true and the match
> > function returns NULL, which propagates to fwnode_typec_switch_get() which
> > makes it look as if the orientation-switch was not described in DT.
> >
> > This is incorrect, because the mux driver will probe a bit later on, but
> > at that point, the caller of fwnode_typec_switch_get() already got the
> > NULL return value. The NULL return value also does not trigger IS_ERR(),
> > therefore the caller driver interprets this as if the orientation-switch
> > is not described in DT, and does not return -EPROBE_DEFER to try again,
> > even if it should.
> >
> > Fix this by checking the class_find_device() return value, and return
> > -EPROBE_DEFER if it is NULL right away. If the return value is not NULL,
> > perform the deduplication test, and if that test passes, consider the
> > return value to be already non-NULL.
> >
> > Fixes: a53b4f9c51a9 ("usb: typec: mux: avoid duplicated orientation switches")
> > Cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Marek Vasut <marex@xxxxxxxxxxxx>
> > ---
> >
> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > Cc: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
> > Cc: Jens Glathe <jens.glathe@xxxxxxxxxxxxxxxxxxxxxx>
> > Cc: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxx>
> > Cc: kernel@xxxxxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > Cc: linux-usb@xxxxxxxxxxxxxxx
> > ---
> > NOTE: A similar change was reverted in
> >        f576c75f95a5 ("Revert "usb: typec: mux: avoid duplicated mux switches"")
> >        Maybe the orientation switch commit also needs a revert ?
> >        Or the mux switch revert can be undone and fixed using this NULL check ?
> > ---
>
> This revert negatively affects Rockchip once my USB-C rework for
> USB-DP lands and I undid it locally. I've just not yet found the
> time to investigate why it regresses the X1E platform to reintroduce
> the feature. Maybe you found the root cause and fix already, but
> investigating with my T14s Gen6 Snapdragon is on my TODO list.
>
> FWIW this patch is
>
> Reviewed-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxx>
Could you revert f576c75f95a5 ("Revert "usb: typec: mux: avoid 
duplicated mux switches"") and apply the following patch (equivalent to 
this patch, applies to mux instead of switch) and see if that fixes the 
T14s for you too then ? If yes, than, I think this might be the proper 
fix rather than the revert:

diff --git a/drivers/usb/typec/mux.c b/drivers/usb/typec/mux.c
index 4a4297f15aad3..afa6fc1813978 100644
--- a/drivers/usb/typec/mux.c
+++ b/drivers/usb/typec/mux.c
@@ -294,6 +294,8 @@ static void *typec_mux_match(const struct 
fwnode_handle *fwnode,

        dev = class_find_device(&typec_mux_class, NULL, fwnode,
                                mux_fwnode_match);
+       if (!dev)
+               return ERR_PTR(-EPROBE_DEFER);

        /* Skip duplicates */
        for (i = 0; i < TYPEC_MUX_MAX_DEVS; i++)
@@ -303,7 +305,7 @@ static void *typec_mux_match(const struct 
fwnode_handle *fwnode,
                }


-       return dev ? to_typec_mux_dev(dev) : ERR_PTR(-EPROBE_DEFER);
+       return to_typec_mux_dev(dev);
 }

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