[U-Boot] [PATCH v1] clk: clk-uclass: Check ops pointer before use it

[Wenyou.Yang at microchip.com]

Add Simon and Andreas in loop

> -----Original Message-----
> From: Stephen Warren [mailto:swarren at wwwdotorg.org]
> Sent: 2016年8月18日 11:56
> To: Wenyou Yang - A41535 <Wenyou.Yang at microchip.com>;
> wenyou.yang at atmel.com
> Cc: u-boot at lists.denx.de; swarren at nvidia.com; michal.simek at xilinx.com
> Subject: Re: [U-Boot] [PATCH v1] clk: clk-uclass: Check ops pointer before use it
> 
> On 08/17/2016 09:53 PM, Wenyou.Yang at microchip.com wrote:
> > Hi Stephen,
> >
> >> -----Original Message-----
> >> From: Stephen Warren [mailto:swarren at wwwdotorg.org]
> >> Sent: 2016年8月18日 11:46
> >> To: Wenyou Yang - A41535 <Wenyou.Yang at microchip.com>;
> >> wenyou.yang at atmel.com
> >> Cc: u-boot at lists.denx.de; swarren at nvidia.com; michal.simek at xilinx.com
> >> Subject: Re: [U-Boot] [PATCH v1] clk: clk-uclass: Check ops pointer
> >> before use it
> >>
> >> On 08/17/2016 06:30 PM, Wenyou.Yang at microchip.com wrote:
> >>> HI Stephen,
> >>>
> >>>> -----Original Message-----
> >>>> From: Stephen Warren [mailto:swarren at wwwdotorg.org]
> >>>> Sent: 2016年8月17日 23:59
> >>>> To: Wenyou Yang <wenyou.yang at atmel.com>
> >>>> Cc: U-Boot Mailing List <u-boot at lists.denx.de>; Stephen Warren
> >>>> <swarren at nvidia.com>; Michal Simek <michal.simek at xilinx.com>
> >>>> Subject: Re: [U-Boot] [PATCH v1] clk: clk-uclass: Check ops pointer
> >>>> before use it
> >>>>
> >>>> On 08/17/2016 01:05 AM, Wenyou Yang wrote:
> >>>>> Add check ops pointer before use it. Otherwise, it will cause the
> >>>>> runtime error for the clk devices without ops callback.
> >>>>
> >>>> Other uclasses like reset, power domain, and mailbox don't do this.
> >>>> All drivers must have an ops pointer, or they can't be useful. I'm
> >>>> not sure this patch is necessary. Is it just a debugging aid so if
> >>>> the driver writer forgets to set the ops pointer the system will
> >>>> error out rather than crashing? If so, a post-bind hook in the
> >>>> uclass that
> >> refuses the driver if it hasn't set the ops pointer would be better.
> >>>
> >>> Sorry, I don't agree with you.
> >>>
> >>> Not all drivers have an ops pointer.
> >>>
> >>> If you grep U_BOOT_DRIVER , you will find that there are some
> >>> drivers without
> >> an ops pointer.
> >>>
> >>> We should not suppose a driver should have something, I think.
> >>
> >> But without an ops pointer, the driver can do nothing and provide no services.
> >> Why is that useful?
> >
> > There are some nodes without compatible in device tree,  as a child of
> > some node, for example, pinctrl child node or for my code peripheral clock node.
> >
> > These nodes also need to be bound before using them. They require such driver
> to bind them.
> 
> That seems unrelated. A node without a compatible value won't instantiate a
> device object, and hence needs no driver.

But there are such nodes and drivers (i.e., U_BOOT_DRIVER) existed in U-Boot, as I said before. 

Is it harmful to add this check?

I know, if not, it will produce a wild pointer, such as NULL->of_xlate.


Best Regards,
Wenyou Yang