linux-kernel - Re: [PATCH 2/8] usb: typec: altmode: add low level altmode configuration helper

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Message-ID: <CAA8EJppf9z+q4_xjQE62Vi-2BiHJpUi7mS0EMSRV_XxbGH==qg@mail.gmail.com>
Date: Tue, 16 Apr 2024 18:20:11 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Konrad Dybcio <konrad.dybcio@...aro.org>
Cc: Heikki Krogerus <heikki.krogerus@...ux.intel.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Bjorn Andersson <andersson@...nel.org>, linux-usb@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 2/8] usb: typec: altmode: add low level altmode
 configuration helper

On Tue, 16 Apr 2024 at 17:57, Konrad Dybcio <konrad.dybcio@...aro.org> wrote:
>
>
>
> On 4/16/24 16:48, Dmitry Baryshkov wrote:
> > On Tue, 16 Apr 2024 at 17:32, Konrad Dybcio <konrad.dybcio@...aro.org> wrote:
> >>
> >>
> >>
> >> On 4/16/24 04:20, Dmitry Baryshkov wrote:
> >>> In some obscure cases (Qualcomm PMIC Glink) altmode is completely
> >>> handled by the firmware. Linux does not get proper partner altmode info.
> >>> Instead we get the notification once the altmode is negotiated and
> >>> entered (or left). However even in such a case the driver has to switch
> >>> board components (muxes, switches and retimers) according to the altmode
> >>> selected by the hardware.
> >>>
> >>> We can not use existing typec_altmode_enter() / typec_altmode_exit() /
> >>> typec_altmode_notify() functions in such a case, since there is no
> >>> corresponding partner's altmode instance.
> >>>
> >>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> >>> ---
> >>
> >> Should this now be called from e.g. typec_almode_notify to limit
> >> duplication?
> >
> > typec_altmode_notify works only if there is an altmode->partner (which
> > we don't have with pmic-glink).
>
> Yes and this seems to be an excerpt from these functions, should they
> now drop that code and call this function instead, so as not to have
> it in the tree twice?

I thought about it, but then I abandoned this idea. The
typec_altmode_notify() has its own use case, normal altmode drivers.
It is an error to call it if there is no partner registered, etc. So I
wanted to preserve error checks in that function instead of dropping
them. The significant part of the code is shared anyway thanks to
typec_altmode_set_switches().

-- 
With best wishes
Dmitry