From: "Vaittinen, Matti" <Matti.Vaittinen@fi.rohmeurope.com>
To: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-i2c@vger.kernel.org" <linux-i2c@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-media@vger.kernel.org" <linux-media@vger.kernel.org>
Cc: Hans Verkuil <hverkuil-cisco@xs4all.nl>,
Jacopo Mondi <jacopo@jmondi.org>,
Kieran Bingham <kieran.bingham@ideasonboard.com>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
Luca Ceresoli <luca@lucaceresoli.net>,
Mark Rutland <mark.rutland@arm.com>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
Peter Rosin <peda@axentia.se>, Rob Herring <robh+dt@kernel.org>,
Sakari Ailus <sakari.ailus@linux.intel.com>,
Vladimir Zapolskiy <vz@mleia.com>,
Wolfram Sang <wsa@the-dreams.de>,
"satish.nagireddy@getcruise.com" <satish.nagireddy@getcruise.com>
Subject: Re: [PATCH v4 0/8] i2c-atr and FPDLink
Date: Mon, 7 Nov 2022 17:47:07 +0000 [thread overview]
Message-ID: <74d8aa71-1133-537d-3de9-e6efd458025f@fi.rohmeurope.com> (raw)
In-Reply-To: <50f0e9a2-33a4-9afb-4105-eadd6da21e99@ideasonboard.com>
Evening Tomi,
On 11/7/22 17:37, Tomi Valkeinen wrote:
> Hi Matti,
>
> On 07/11/2022 16:37, Vaittinen, Matti wrote:
>
> I only had time to have a brief look at your code, but I have a few
> quick questions.
>
>> I think it was Tomi who asked me the benefit of using MFD. In some cases
>> the digital interface towards pinctrl/GPIO or other functional blocks in
>> SER/DES is re-used from other products - or the blocks are re-used on
>> other products. Separating them in own platform-drivers is a nice way to
>> re-use drivers and avoid code duplication.
>
> Is there anything that prevents us (or makes it difficult) from
> refactoring a "monolithic" driver into an MFD later? If we see such IP
> re-use, can we then move to an MFD?
I haven't done such conversion. I think the work for doing the
conversion at later phase is roughly same it would be now. However,
synchronizing such change with related subsystem trees might be some
extra work.
> I admit I have never written an MFD driver (but I have hacked with a few
> years back). As I see it, the "subcomponents" in FPDLink ICs are more or
> less tied to the FPDLink. It's not like they're independent. Compare to,
> for example, a PMIC which provides regulators and GPIOs, and possibly
> the only shared part between those two features are the pins.
I think that in SerDes driver case the benefit may come from re-use and
clarity. Smaller drivers tend to be easier to comprehend, although I
liked the way you had divided the drivers in sections.
> So, I think I'm still wondering about the benefit...
>
> In the current version I have the deser driver supporting UB960 and
> UB9702. I guess I could split those into separate drivers,
I wouldn't break the driver per IC. If the ICs are similar enough to be
nicely handled by same driver, then they probably should.
>
> The benefit would be more obvious if there was some other type of IC
> that uses the same IP subcomponents.
Yes. Same or similar subcomponents. This indeed is the benefit I see. I
don't know if TI could use same - say GPIO - control logic on another
type of device? Or, maybe separating the logic could guide one to use
some generic stuff like regmap_gpio driver? And finally, submitting
small platform drivers via respective subsystems can yield better review ;)
>
> Also, isn't the use or non-use of MFD strictly a driver private thing,
I am tempted to say "yes", but when giving it a thought - it's really
not fully that. Splitting a driver to subdrivers can allow re-use of
subcomponents by unrelated ICs. OTOH, always stuffing everything in a
driver "because it is driver internal decision" can lead to code
duplication and bloat.
> it should not affect any shared parts or shared designs? In other words,
> if you have your ROHM hat on, why do you care how the UB9xx driver is
> structured internally? ;)
As I wrote:
> > Please, do not treat this as a requirement - please treat it as a
food for thoughts ;)
Eg, I am not trying to tell you how to do the UB9xx drivers. I just
think that considering another design _might_ result more optimal design
- but I do leave the decision to you who know this area better than I do.
Yours
-- Matti
--
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland
~~ When things go utterly wrong vim users can always type :help! ~~
prev parent reply other threads:[~2022-11-07 17:48 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-01 13:20 [PATCH v4 0/8] i2c-atr and FPDLink Tomi Valkeinen
2022-11-01 13:20 ` [PATCH v4 1/8] i2c: core: let adapters be notified of client attach/detach Tomi Valkeinen
2022-11-01 13:20 ` [PATCH v4 2/8] i2c: add I2C Address Translator (ATR) support Tomi Valkeinen
2022-11-01 14:30 ` Andy Shevchenko
2022-11-04 11:59 ` Tomi Valkeinen
2022-11-04 12:38 ` Andy Shevchenko
2022-11-04 15:26 ` Tomi Valkeinen
2022-11-04 17:27 ` Andy Shevchenko
2022-11-07 11:40 ` Luca Ceresoli
2022-12-08 7:56 ` Tomi Valkeinen
2022-11-01 13:20 ` [PATCH v4 3/8] dt-bindings: media: add bindings for TI DS90UB960 Tomi Valkeinen
2022-11-01 16:47 ` Rob Herring
2022-11-02 17:26 ` Rob Herring
2022-11-03 11:50 ` Tomi Valkeinen
2022-11-03 12:13 ` Vaittinen, Matti
2022-11-03 12:32 ` Tomi Valkeinen
2022-11-11 16:26 ` Luca Ceresoli
2022-12-08 9:23 ` Tomi Valkeinen
2022-11-11 16:32 ` Luca Ceresoli
2022-11-11 16:35 ` Luca Ceresoli
2022-11-01 13:20 ` [PATCH v4 4/8] dt-bindings: media: add bindings for TI DS90UB913 Tomi Valkeinen
2022-11-01 16:47 ` Rob Herring
2022-11-02 17:27 ` Rob Herring
2022-11-01 13:20 ` [PATCH v4 5/8] dt-bindings: media: add bindings for TI DS90UB953 Tomi Valkeinen
2022-11-01 16:47 ` Rob Herring
2022-11-01 13:20 ` [PATCH v4 6/8] media: i2c: add DS90UB960 driver Tomi Valkeinen
2022-11-02 8:05 ` Tomi Valkeinen
2022-11-01 13:20 ` [PATCH v4 7/8] media: i2c: add DS90UB913 driver Tomi Valkeinen
2022-11-01 13:20 ` [PATCH v4 8/8] media: i2c: add DS90UB953 driver Tomi Valkeinen
2022-11-07 11:48 ` [PATCH v4 0/8] i2c-atr and FPDLink Luca Ceresoli
2022-11-07 12:12 ` Vaittinen, Matti
2022-11-07 12:12 ` Tomi Valkeinen
2022-11-07 14:37 ` Vaittinen, Matti
2022-11-07 15:37 ` Tomi Valkeinen
2022-11-07 17:47 ` Vaittinen, Matti [this message]
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