Messages in this thread | | | Subject | Re: [PATCH RESEND 6/6] clk: s5p-g2d: Fix incorrect usage of IS_ERR_OR_NULL | From | Tony Prisk <> | Date | Wed, 02 Jan 2013 18:31:53 +1300 |
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On Wed, 2013-01-02 at 08:10 +0300, Dan Carpenter wrote: > clk_get() returns NULL if CONFIG_HAVE_CLK is disabled. > > I told Tony about this but everyone has been gone with end of year > holidays so it hasn't been addressed. > > Tony, please fix it so people don't apply these patches until > clk_get() is updated to not return NULL. It sucks to have to revert > patches. > > regards, > dan carpenter
I posted the query to Mike Turquette, linux-kernel and linux-arm-kernel mailing lists, regarding the return of NULL when HAVE_CLK is undefined.
Short Answer: A return value of NULL is valid and not an error therefore we should be using IS_ERR, not IS_ERR_OR_NULL on clk_get results.
I see the obvious problem this creates, and asked this question:
If the driver can't operate with a NULL clk, it should use a IS_ERR_OR_NULL test to test for failure, rather than IS_ERR.
And Russell's answer:
Why should a _consumer_ of a clock care? It is _very_ important that people get this idea - to a consumer, the struct clk is just an opaque cookie. The fact that it appears to be a pointer does _not_ mean that the driver can do any kind of dereferencing on that pointer - it should never do so.
Thread can be viewed here: https://lkml.org/lkml/2012/12/20/105
Regards Tony Prisk
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