netdev - Re: [PATCH RFC v6 2/6] dpll: Add DPLL framework base functions

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Date: Tue, 9 May 2023 17:21:42 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Paolo Abeni <pabeni@...hat.com>,
	"Kubalewski, Arkadiusz" <arkadiusz.kubalewski@...el.com>,
	Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
	Vadim Fedorenko <vadfed@...a.com>,
	Jonathan Lemon <jonathan.lemon@...il.com>, poros <poros@...hat.com>,
	mschmidt <mschmidt@...hat.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	linux-arm-kernel@...ts.infradead.org,
	"linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
	"Olech, Milena" <milena.olech@...el.com>,
	"Michalik, Michal" <michal.michalik@...el.com>
Subject: Re: [PATCH RFC v6 2/6] dpll: Add DPLL framework base functions

Tue, May 09, 2023 at 04:52:47PM CEST, kuba@...nel.org wrote:
>On Tue, 9 May 2023 09:53:07 +0200 Jiri Pirko wrote:
>> >Yup. Even renaming EXT to something that's less.. relative :(  
>> 
>> Suggestion?
>
>Well, is an SMT socket on the board an EXT pin?
>Which is why I prefer PANEL.

Makes sense.
To speak code, we'll have:

/**
 * enum dpll_pin_type - defines possible types of a pin, valid values for
 *   DPLL_A_PIN_TYPE attribute
 * @DPLL_PIN_TYPE_UNSPEC: unspecified value
 * @DPLL_PIN_TYPE_MUX: aggregates another layer of selectable pins
 * @DPLL_PIN_TYPE_PANEL: physically facing user, for example on a front panel
 * @DPLL_PIN_TYPE_SYNCE_ETH_PORT: ethernet port PHY's recovered clock
 * @DPLL_PIN_TYPE_INT_OSCILLATOR: device internal oscillator
 * @DPLL_PIN_TYPE_GNSS: GNSS recovered clock
 */
enum dpll_pin_type {
        DPLL_PIN_TYPE_UNSPEC,
        DPLL_PIN_TYPE_MUX,
        DPLL_PIN_TYPE_PANEL,
        DPLL_PIN_TYPE_SYNCE_ETH_PORT,
        DPLL_PIN_TYPE_INT_OSCILLATOR,
        DPLL_PIN_TYPE_GNSS,

        __DPLL_PIN_TYPE_MAX,
        DPLL_PIN_TYPE_MAX = (__DPLL_PIN_TYPE_MAX - 1)
};


>
>> >> Well sure, in case there is no "label" attr for the rest of the types.
>> >> Which I believe it is, for the ice implementation in this patchset.
>> >> Otherwise, there is no way to distinguish between the pins.
>> >> To have multiple attrs for label for multiple pin types does not make
>> >> any sense to me, that was my point.  
>> >
>> >Come on, am I really this bad at explaining this?  
>> 
>> Or perhaps I'm just slow.
>> 
>> >If we make a generic "label" attribute driver authors will pack
>> >everything they want to expose to the user into it, and then some.  
>> 
>> What's difference in generic label string attr and type specific label
>> string attr. What is stopping driver developers to pack crap in either
>> of these 2. Perhaps I'm missing something. Could you draw examples?
>> 
>> >So we need attributes which will feel *obviously* *wrong* to abuse.  
>> 
>> Sure, I get what you say and agree. I'm just trying to find out the
>> actual attributes :)
>
>PANEL label must match the name on the panel. User can take the card
>into their hand, look at the front, and there should be a label/sticker/
>/engraving which matches exactly what the kernel reports.
>
>If the label is printed on the board it's a BOARD_LABEL, if it's the
>name of a trace in board docs it's a BOARD_TRACE, if it's a pin of 
>the ASIC it's a PACKAGE_PIN.
>
>If it's none of those, or user does not have access to the detailed
>board / pinout - don't use the label.

To speak code, we'll have:
DPLL_A_PIN_PANEL_LABEL (string)
   available always when attr[DPLL_A_PIN_TYPE] == DPLL_PIN_TYPE_PANEL
DPLL_A_PIN_BOARD_LABEL (string)
   may be available for any type, optional
DPLL_A_PIN_BOARD_TRACE (string)
   may be available for any type, optional
DPLL_A_PIN_PACKAGE_PIN (string)
   may be available for any type, optional

Makes sense?

But this does not prevent driver developer to pack random crap in the
string anyway :/