linux-kernel - Re: [PATCH] clk: Add functions to get optional clocks

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Date:   Wed, 18 Jul 2018 15:19:21 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Russell King <linux@...linux.org.uk>
Cc:     Phil Edworthy <phil.edworthy@...esas.com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Simon Horman <horms@...ge.net.au>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-clk <linux-clk@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] clk: Add functions to get optional clocks

Hi Russell,

On Wed, Jul 18, 2018 at 3:02 PM Russell King - ARM Linux
<linux@...linux.org.uk> wrote:
> On Wed, Jul 18, 2018 at 01:57:38PM +0100, Phil Edworthy wrote:
> > Behaves the same as (devm_)clk_get except where there is no clock
> > producer. In this case, instead of returning -ENOENT, the function
> > returns NULL. This makes error checking simpler and allows
> > clk_prepare_enable, etc to be called on the returned reference
> > without additional checks.
>
> How does this work with non-DT systems, where looking a clock up which
> isn't yet registered with clkdev returns -ENOENT ?
>
> (clkdev doesn't know when all clocks are registered with it.)

Good question.

I guess all drivers trying to handle optional clocks this way are already broken
on non-DT systems where clocks may be registered late...

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds