netdev - Re: [PATCH] net/irda: add clk_prepare/clk_unprepare to pxaficp

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Date:	Fri, 16 Mar 2012 23:10:47 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	philipp.zabel@...il.com
Cc:	netdev@...r.kernel.org, eric.y.miao@...il.com,
	haojian.zhuang@...vell.com, samuel@...tiz.org
Subject: Re: [PATCH] net/irda: add clk_prepare/clk_unprepare to pxaficp_ir

From: Philipp Zabel <philipp.zabel@...il.com>
Date: Thu, 15 Mar 2012 19:19:29 +0100

> This patch adds clk_prepare/clk_unprepare calls to the pxaficp_ir
> driver by using the helper functions clk_prepare_enable and
> clk_disable_unprepare.
> 
> Signed-off-by: Philipp Zabel <philipp.zabel@...il.com>

This is terrible.

So the problem was that clk_enable can't be invoked from atomic
context, because it wants to take a mutex for some implementation.

Therefore an existing routine with well defined semantics,
clk_enable(), was turned into a NOP.

And this silently breaks drivers.

Instead of silently breaking things, make direct
clk_enable()/clk_disable() invocations either result in a compile
error or a run-time BUG_ON().

There are other ways this could have been handled as well.

But just making clk_{enable,disable}() essentially stop working
was not a very good one at all.

I'll apply this patch to net-next, but I just wanted to point out
what an absolutely brain-dead way this was handled.
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