linux-kernel - Re: [PATCH v6 01/24] i2c-mux: add common data for every i2c-mux instance

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Date:	Fri, 15 Apr 2016 13:23:19 +0200
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Peter Rosin <peda@...ator.liu.se>
Cc:	linux-kernel@...r.kernel.org, Peter Rosin <peda@...ntia.se>,
	Jonathan Corbet <corbet@....net>,
	Peter Korsgaard <peter.korsgaard@...co.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Jonathan Cameron <jic23@...nel.org>,
	Hartmut Knaack <knaack.h@....de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Peter Meerwald <pmeerw@...erw.net>,
	Antti Palosaari <crope@....fi>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Rob Herring <robh+dt@...nel.org>,
	Frank Rowand <frowand.list@...il.com>,
	Grant Likely <grant.likely@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"David S. Miller" <davem@...emloft.net>,
	Kalle Valo <kvalo@...eaurora.org>,
	Joe Perches <joe@...ches.com>, Jiri Slaby <jslaby@...e.com>,
	Daniel Baluta <daniel.baluta@...el.com>,
	Adriana Reus <adriana.reus@...el.com>,
	Lucas De Marchi <lucas.demarchi@...el.com>,
	Matt Ranostay <matt.ranostay@...el.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Terry Heo <terryheo@...gle.com>,
	Hans Verkuil <hans.verkuil@...co.com>,
	Arnd Bergmann <arnd@...db.de>,
	Tommi Rantala <tt.rantala@...il.com>,
	linux-i2c@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-iio@...r.kernel.org, linux-media@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v6 01/24] i2c-mux: add common data for every i2c-mux
 instance


> > I'd suggest to rename 'adapters' into 'num_adapters' throughout this
> > patch. I think it makes the code a lot easier to understand.
> 
> Hmm, you mean just the variable names, right? And not function names
> such as i2c_mux_reserve_(num_)adapters?

Yes, only variable names.

> > Despite that I wonder why not using some of the realloc functions, I
> 
> When I wrote it, I found no devm_ version of realloc. I'm not finding
> anything now either...

Right, there is no devm_ version of it :(

> > wonder even more if we couldn't supply num_adapters to i2c_mux_alloc()
> > and reserve the memory statically. i2c busses are not
> > dynamic/hot-pluggable so that should be good enough?
> 
> Yes, that would work, but it would take some restructuring in some of
> the drivers that currently don't know how many child adapters they
> are going to need when they call i2c_mux_alloc.

Which ones?

> Because you thought about removing i2c_mux_reserve_adapters completely,
> and not provide any means of adding more adapters than specified in
> the i2c_mux_alloc call, right?

Yes. I assumed I2C to be static enough that such information is known in
advance.

> > Ignoring the 80 char limit here makes the code more readable.
> 
> That is only true if you actually have more than 80 characters, so I don't
> agree. Are you adamant about it? (I'm not)

No. Keep it if you prefer it.

> >> +EXPORT_SYMBOL_GPL(i2c_mux_one_adapter);
> > 
> > Are you sure the above function pays off? Its argument list is very
> > complex and it doesn't save a lot of code. Having seperate calls is
> > probably more understandable in drivers? Then again, I assume it makes
> > the conversion of existing drivers easier.
> 
> I added it in v4, you can check earlier versions if you like. Without
> it most gate-muxes (i.e. typically the muxes in drivers/media) grew
> since the i2c_add_mux_adapter call got replaced by two calls, i.e.
> i2c_mux_alloc followed by i2c_max_add_adapter, and coupled with
> error checks made it look more complex than before. So, this wasn't
> much of a cleanup from the point of those drivers.

Hmm, v3 didn't have the driver patches posted with it. Can you push it
to your branch? I am also not too strong with this one, but having a
look how it looks without would be nice.


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