Re: [PATCH -next] drm/tegra: fix return value check

[Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>]

On 10/28/2013 04:38 PM, Thierry Reding wrote:
> On Mon, Oct 28, 2013 at 03:51:32PM -0600, Stephen Warren wrote:
>> On 10/28/2013 02:53 AM, Thierry Reding wrote:
>>> On Mon, Oct 21, 2013 at 11:34:07AM +0800, Wei Yongjun wrote:
>>>> From: Wei Yongjun <yongjun_wei-zrsr2BFq86L20UzCJQGyNP8+0UxHXcjY@public.gmane.org>
>>>> 
>>>> In case of error, the function clk_get_parent() and 
>>>> devm_ioremap_resource() returns ERR_PTR() and never returns
>>>> NULL. The NULL test in the return value check should be
>>>> replaced with IS_ERR().
>>>> 
>>>> Signed-off-by: Wei Yongjun <yongjun_wei-zrsr2BFq86L20UzCJQGyNP8+0UxHXcjY@public.gmane.org>
>>>> --- drivers/gpu/drm/tegra/dsi.c | 6 +++--- 1 file changed, 3 
>>>> insertions(+), 3 deletions(-)
>>> 
>>> I've applied this, but with the first hunk removed, since
>>> looking at the implementation of clk_get_parent() it can
>>> actually return NULL. In fact it seems like it will never
>>> return ERR_PTR().
>>> 
>>> I've also updated the commit message to reflect that.
>> 
>> Hmm. The documentation for clk_get() says:
> 
> The patch didn't check the return value clk_get() but
> clk_get_parent(). Here's the implementation:
> 
> struct clk *__clk_get_parent(struct clk *clk) { return !clk ? NULL
> : clk->parent; }
> 
> Note that clk_get_parent() in simply a locked version of the above.
> That will obviously only return ERR_PTR() if clk->parent happens to
> be set to one such value, which I don't think will ever happen.

Ah. That looks like a bug in __clk_get_parent() then, since !clk
doesn't sound like  the correct error case for it to be checking.
Shouldn't it return IS_ERR(clk) ? clk : clk->parent? Either that, or
clk_get() shouldn't return an error value if the rest of the clock
code doesn NULL checks.