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

[Wenyou.Yang at microchip.com]

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.


Best Regards,
Wenyou Yang