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

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Date:   Thu, 16 Mar 2023 13:31:45 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     "Kubalewski, Arkadiusz" <arkadiusz.kubalewski@...el.com>
Cc:     Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
        Vadim Fedorenko <vadfed@...a.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Jonathan Lemon <jonathan.lemon@...il.com>,
        Paolo Abeni <pabeni@...hat.com>, poros <poros@...hat.com>,
        mschmidt <mschmidt@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.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

Wed, Mar 15, 2023 at 10:22:33AM CET, jiri@...nulli.us wrote:
>Tue, Mar 14, 2023 at 06:50:57PM CET, arkadiusz.kubalewski@...el.com wrote:
>>>From: Jiri Pirko <jiri@...nulli.us>
>>>Sent: Tuesday, March 14, 2023 10:22 AM
>>>
>>>Mon, Mar 13, 2023 at 11:59:32PM CET, vadim.fedorenko@...ux.dev wrote:
>>>>On 13.03.2023 16:21, Jiri Pirko wrote:
>>>>> Sun, Mar 12, 2023 at 03:28:03AM CET, vadfed@...a.com wrote:

[...]


>>>>> > +	     const struct dpll_pin_properties *prop)
>>>>> > +{
>>>>> > +	struct dpll_pin *pos, *ret = NULL;
>>>>> > +	unsigned long index;
>>>>> > +
>>>>> > +	mutex_lock(&dpll_pin_xa_lock);
>>>>> > +	xa_for_each(&dpll_pin_xa, index, pos) {
>>>>> > +		if (pos->clock_id == clock_id &&
>>>>> > +		    pos->dev_driver_id == device_drv_id &&
>>>>> > +		    pos->module == module) {
>>>>>
>>>>> Compare prop as well.
>>>>>
>>>>> Can't the driver_id (pin index) be something const as well? I think it
>>>>> should. And therefore it could be easily put inside.
>>>>>
>>>>
>>>>I think clock_id + dev_driver_id + module should identify the pin exactly.
>>>>And now I think that *prop is not needed here at all. Arkadiusz, any
>>>>thoughts?
>>>
>>>IDK, no strong opinion on this. I just thought it may help to identify
>>>the pin and avoid potential driver bugs. (Like registering 2 pins with

Was thinking about this some more, I think that it would be good to
store and check properties in case of pin_get() call. If the driver does
call for the second time pin_get() for the same pin (clockid,pin_index)
with different prop, it is buggy and WARN_ON should be triggered.
WARN_ON check should compare the actual struct, not just pointer.

[...]