netdev - Re: [RFC PATCH v7 0/8] Create common DPLL configuration API

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Date: Wed, 17 May 2023 12:18:37 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Vadim Fedorenko <vadfed@...a.com>,
	Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>
Cc: Jakub Kicinski <kuba@...nel.org>,
	Jonathan Lemon <jonathan.lemon@...il.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Milena Olech <milena.olech@...el.com>,
	Michal Michalik <michal.michalik@...el.com>,
	linux-arm-kernel@...ts.infradead.org,
	Vadim Fedorenko <vadim.fedorenko@...ux.dev>, poros@...hat.com,
	mschmidt@...hat.com, netdev@...r.kernel.org,
	linux-clk@...r.kernel.org
Subject: Re: [RFC PATCH v7 0/8] Create common DPLL configuration API

Let me summarize the outcome of the discussion between me and Jakub
regarding attributes, handles and ID lookups in the RFCv7 thread:

--------------------------------------------------------------
** Needed changes for RFCv8 **

1) No scoped indexes.
   The indexes passed from driver to dpll core during call of:
        dpll_device_get() - device_idx
        dpll_pin_get() - pin_idx
   should be for INTERNAL kernel use only and NOT EXPOSED over uapi.
   Therefore following attributes need to be removed:
   DPLL_A_PIN_IDX
   DPLL_A_PIN_PARENT_IDX

2) For device, the handle will be DPLL_A_ID == dpll->id.
   This will be the only handle for device for every
   device related GET, SET command and every device related notification.
   Note: this ID is not deterministing and may be different depending on
   order of device probes etc.

3) For pin, the handle will be DPLL_A_PIN_ID == pin->id
   This will be the only handle for pin for every
   pin related GET, SET command and every pin related notification.
   Note: this ID is not deterministing and may be different depending on
   order of device probes etc.

4) Remove attribute:
   DPLL_A_PIN_LABEL
   and replace it with:
   DPLL_A_PIN_PANEL_LABEL (string)
   DPLL_A_PIN_XXX (string)
   where XXX is a label type, like for example:
     DPLL_A_PIN_BOARD_LABEL
     DPLL_A_PIN_BOARD_TRACE
     DPLL_A_PIN_PACKAGE_PIN

5) Make sure you expose following attributes for every device and
   pin GET/DUMP command reply message:
   DPLL_A_MODULE_NAME
   DPLL_A_CLOCK_ID

6) Remove attributes:
   DPLL_A_DEV_NAME
   DPLL_A_BUS_NAME
   as they no longer have any value and do no make sense (even in RFCv7)

--------------------------------------------------------------
** Lookup commands **

Basically these would allow user to query DEVICE_ID and PIN_ID
according to provided atributes (see examples below).

These would be from my perspective optional for this patchsets.
I believe we can do it as follow-up if needed. For example for mlx5
I don't have usecase for it, since I can consistently get PIN_ID
using RT netlink for given netdev. But I can imagine that for non-SyncE
dpll driver this would make sense to have.

1) Introduce CMD_GET_ID - query the kernel for a dpll device
                          specified by given attrs
   Example:
   -> DPLL_A_MODULE_NAME
      DPLL_A_CLOCK_ID
      DPLL_A_TYPE
   <- DPLL_A_ID
   Example:
   -> DPLL_A_MODULE_NAME
      DPLL_A_CLOCK_ID
   <- DPLL_A_ID
   Example:
   -> DPLL_A_MODULE_NAME
   <- -EINVAL (Extack: "multiple devices matched")

   If user passes a subset of attrs which would not result in
   a single match, kernel returns -EINVAL and proper extack message.

2) Introduce CMD_GET_PIN_ID - query the kernel for a dpll pin
                              specified by given attrs
   Example:
   -> DPLL_A_MODULE_NAME
      DPLL_A_CLOCK_ID
      DPLL_A_PIN_TYPE
      DPLL_A_PIN_PANEL_LABEL
   <- DPLL_A_PIN_ID
   Example:
   -> DPLL_A_MODULE_NAME
      DPLL_A_CLOCK_ID
   <- DPLL_A_PIN_ID    (There was only one pin for given module/clock_id)
   Example:
   -> DPLL_A_MODULE_NAME
      DPLL_A_CLOCK_ID
   <- -EINVAL (Extack: "multiple pins matched")

   If user passes a subset of attrs which would not result in
   a single match, kernel returns -EINVAL and proper extack message.