Re: [PATCH 2/4] arch/arm/mach-at91/clock.c: Add missing IS_ERR test

From: Ryan Mallon
Date: Mon Jan 24 2011 - 16:06:15 EST

On 01/25/2011 10:01 AM, Julia Lawall wrote:
> On Tue, 25 Jan 2011, Ryan Mallon wrote:
>> On 01/25/2011 09:28 AM, Julia Lawall wrote:
>>>> Julia is correct. Some architectures can return NULL from clk_get, but I
>>>> didn't check the at91 before posting :-/. If we can't return NULL from
>>>> clk_get then we shouldn't bother checking for it. I do think we should
>>>> drop the !IS_ERR(clk_get(dev, func)) check though.
>>> It seems a bit subtle, because the clk manipulated by clk_get in the call
>>> of clk_get(dev, func) is not necessarily the same as the one in
>>> clock_associate. But perhaps this is the only possibility in practice?
>> Not sure I follow. The at91 clk_get does not modify the clk. In
>> at91_clock_associate we have:
>> clk->function = func;
>> clk->dev = dev;
>> and in clk_get we have:
>> if (clk->function && (dev == clk->dev) &&
>> strcmp(id, clk->function) == 0)
>> return clk;
>> So at91_clock_associate sets the function for a clock, and clk_get
>> returns clocks based on the function association if the name lookup
>> fails. The only caveat to this is that the the clock function name
>> (clk->function) is not the same as any others clock's clk->name.
> Right, that was what I was worried about. That one would find the same
> information already present but somewhere else. But perhaps it can't
> happen, or it doesn't matter if it does?

I think that users are expected to ensure that clock names and clock
function names do not overlap.


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