linux-kernel - Re: [PATCH v2 6/8] media: i2c: ds90ub953: Restructure clkout management

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Message-ID: <2e2417fb-97a1-7153-6ba9-88a6d50f962a@ideasonboard.com>
Date:   Fri, 21 Jul 2023 16:23:54 +0300
From:   Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To:     Andy Shevchenko <andriy.shevchenko@...el.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Luca Ceresoli <luca.ceresoli@...tlin.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Hans Verkuil <hverkuil@...all.nl>,
        Satish Nagireddy <satish.nagireddy@...cruise.com>,
        Matti Vaittinen <mazziesaccount@...il.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 6/8] media: i2c: ds90ub953: Restructure clkout
 management

On 21/07/2023 13:29, Andy Shevchenko wrote:
> On Thu, Jul 20, 2023 at 01:30:37PM +0300, Tomi Valkeinen wrote:
>> Separate clkout calculations and register writes into two functions:
>> ub953_calc_clkout_params and ub953_write_clkout_regs, and add a struct
>> ub953_clkout_data that is used to store the clkout parameters.
>>
>> This simplifies the clkout management.
> 
> ...
> 
>> +struct ub953_clkout_data {
>> +	u32 hs_div;
>> +	u32 m;
>> +	u32 n;
> 
> I don't think it makes driver worse. The V4L2 UAPI has similar struct which is
> used widely, hence I see no issues in using u32_fract here.

I think it makes sense to use u32_fract in common code. My argument for 
not using it here is:

- There is no actual functionality that u32_fract brings, so it's really 
only about field naming
- m and n matches the terms in the HW documentation, making it easier to 
compare the code and the docs
- This is private to the driver
- I'm (currently) the most likely person to edit the driver, and I would 
have to check which one that numerator/denominator was again when 
looking at this part of the code (but maybe I would learn eventually)

So, in my view, the change doesn't really have any pros but does have cons.

That said, it's not a biggie. If others chime in and say it's a good 
idea to use u32_fract, I'm fine doing that change.

  Tomi