Messages in this thread | | | Date | Fri, 8 Apr 2016 10:52:57 +0900 | Subject | Re: [PATCH v2] clk: let clk_disable() return immediately if clk is NULL or error | From | Masahiro Yamada <> |
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Hi Stephen,
2016-04-08 9:33 GMT+09:00 Stephen Boyd <sboyd@codeaurora.org>: > On 04/05, Masahiro Yamada wrote: >> The clk_disable() in the common clock framework (drivers/clk/clk.c) >> returns immediately if a given clk is NULL or an error pointer. It >> allows clock consumers to call clk_disable() without IS_ERR_OR_NULL >> checking if drivers are only used with the common clock framework. >> >> Unfortunately, NULL/error checking is missing from some of non-common >> clk_disable() implementations. This prevents us from completely >> dropping NULL/error checking from callers. Let's make it tree-wide >> consistent by adding IS_ERR_OR_NULL(clk) to all callees. >> >> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> >> Acked-by: Greg Ungerer <gerg@uclinux.org> >> Acked-by: Wan Zongshun <mcuos.com@gmail.com> >> --- >> >> Stephen, >> >> This patch has been unapplied for a long time. >> >> Please let me know if there is something wrong with this patch. >> > > I'm mostly confused why we wouldn't want to encourage people to > call clk_disable or unprepare on a clk that's an error pointer. > Typically an error pointer should be dealt with, instead of > silently ignored, so why wasn't it dealt with by passing it up > the probe() path? >
This makes our driver programming life easier.
For example, let's see drivers/tty/serial/8250/8250_of.c
The "clock-frequency" DT property takes precedence over "clocks" property. So, it is valid to probe the driver with a NULL pointer for info->clk.
if (of_property_read_u32(np, "clock-frequency", &clk)) {
/* Get clk rate through clk driver if present */ info->clk = devm_clk_get(&ofdev->dev, NULL); if (IS_ERR(info->clk)) { dev_warn(&ofdev->dev, "clk or clock-frequency not defined\n"); return PTR_ERR(info->clk); }
ret = clk_prepare_enable(info->clk); if (ret < 0) return ret;
clk = clk_get_rate(info->clk); }
As a result, we need to make sure the clk pointer is valid before calling clk_disable_unprepare().
If we could support pointer checking in callees, we would be able to clean-up lots of clock consumers.
-- Best Regards Masahiro Yamada
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