linux-kernel - Re: [RESEND PATCH v4 0/8] i2c: Relax mandatory I2C ID table passing

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Message-ID: <20151001205035.GB7514@katana>
Date:	Thu, 1 Oct 2015 22:50:35 +0200
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	Javier Martinez Canillas <javier@....samsung.com>,
	Kieran Bingham <kieranbingham@...il.com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
	grant.likely@...aro.org
Subject: Re: [RESEND PATCH v4 0/8] i2c: Relax mandatory I2C ID table passing


> > Yes but that is not true for drivers that support both OF and legacy board
> > files. For those drivers, there will be a lot of boiler plate code duplicated
> > that would look something like:
> > 
> >      unsigned long data;
> >      struct of_device_id *match;
> >      struct i2c_devicd_id *id;
> > 
> >      if (i2c->dev.of_node) {
> >             match = i2c_of_match_device(of_match_table, i2c);
> > 	    if (!match)
> > 	           return -EINVAL;
> > 
> >             data = (unsigned long)match->data;
> >      } else {
> >             id = i2c_match_id(id_table, i2c);
> > 	    if (!id)
> > 	           return -EINVAL;
> > 
> >             data = id->driver_data;
> >      }

I said this before: It is not only the additional code, I think it is
quite unelegant to to do the matching again which has already been done.
(and DT boottime has already increased, partly due to the excessive
string matching). Also, I wouldn't like to see an I2C specific solution;
this problem exists for other subsystems, too.

> I'm fine with a new API for this stuff.  I'm even happy to go ahead
> and code it up, but it's important to note that this is work which
> should be based on this set and not a blocker for this set to be
> accepted.

Is that a promise? :)

> The correct approach is the former.  One of the aims of this set was
> to bring the I2C .probe() call-back more into line with the majority
> of the other .probe() calls in the kernel i.e. with only a single
> parameter.  I'm really not a fan of passing some random void pointer

Yes, I like this about this series.

> in.  Using a look-up call to fetch ACPI/OF/I2C/etc data is the current
> norm and is a very viable option.

It is the status quo, but that doesn't make it better IMO.

> Wolfram, please (finally :D) take this set.

I tend to give in ;) Maybe we can talk in Dublin a bit about a possible
next step after this series?

Thanks,

   Wolfram


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