Thread (25 messages) 25 messages, 6 authors, 2011-02-25

Re: [PATCH] i2c-gpio: add devicetree support

From: Håvard Skinnemoen <hidden>
Date: 2011-01-31 22:35:34
Also in: linux-i2c, lkml

Hi,

On Mon, Jan 31, 2011 at 12:09 AM, Grant Likely
[off-list ref] wrote:
On Sun, Jan 30, 2011 at 8:26 PM, Håvard Skinnemoen
[off-list ref] wrote:
quoted
Hi,

On Sun, Jan 30, 2011 at 7:56 AM, Thomas Chou [off-list ref] wrote:
quoted
From: Albert Herranz <redacted>

This patch is based on an earlier patch from Albert Herranz,
http://git.infradead.org/users/herraa1/gc-linux-2.6.git/commit/
9854eb78607c641ab5ae85bcbe3c9d14ac113733
That commit has a single-line description of which I don't understand
a single word (unless "wii" is what I think it is, which seems
likely). Could you please explain how that commit relates to this
patch?
The URL got wrapped.  Try this one (assuming my mailer doesn't wrap it):

http://git.infradead.org/users/herraa1/gc-linux-2.6.git/commit/9854eb78607c641ab5ae85bcbe3c9d14ac113733
Ok, that seems to be a _bit_ more related, but not that much. I'd
really prefer a patch description which can stand on its own.
quoted
quoted
The dts binding is modified as Grant suggested. The of probing
is merged inline instead of a separate file. It uses the newer
of gpio probe.
It seems like a terrible idea to merge firmware-specific code into the
driver. Is there are reason why of-based platforms can't just pass the
data they need in pdata like everyone else?
Overall Thomas is doing the right thing here.  The driver data has to
be decoded *somewhere*, but since that code is definitely
driver-specific (as opposed to platform, subsystem, or arch specific)
putting it into the driver is absolutely the right thing to do.  Quite
a few drivers now do exactly this.
Ok, I'm convinced that this is the right thing to do.
It is however generally a wise practice to limit the of-support code
to a hook in the drivers probe hook, and as you point out, care must
be taken to make sure both CONFIG_OF and !CONFIG_OF kernel builds
work.
quoted
Not saying that it necessarily _is_ a terrible idea, but I think the
reasoning behind it needs to be included in the patch description.
Nah, he doesn't really need to defend this since it is a well
established pattern.  device tree support is in core code now (see
of_node an of_match_table in include/linux/device.h), and other
drivers do exactly this.
Well, perhaps you're right, but I still think the patch description is
a bit on the thin side. In particular, terms like "as Grant suggested"
isn't very helpful for people like me who don't know what you
suggested (even though I'm sure it was a good suggestion).

I think the patch lacks a good description of what's being changed and
why. The references may be nice to have as a supplement to that, but
describing things entirely in terms of some unknown e-mail discussion
that happened earlier is not very helpful for people who want to
figure out what's going on a couple of months or years from now.

Havard
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