Re: HSI: hsi: Introducing HSI framework

[Carlos Chinea <carlos.chinea@nokia.com>]

Hi Greg,

Thanks for the review.

On Mon, 2012-04-02 at 16:41 -0700, ext Greg KH wrote:
> On Mon, Apr 02, 2012 at 04:56:07PM +0000, Linux Kernel Mailing List wrote:
> > +static void hsi_controller_release(struct device *dev __maybe_unused)
> > +{
> > +}
> > +
> > +static void hsi_port_release(struct device *dev __maybe_unused)
> > +{
> > +}
> 
> As per the documentation in the kernel tree, I get to mock you
> mercilessly for doing something as foolish as this.  You are not smarter
> than the kernel and don't think that you got rid of the kernel warning
> properly by doing this.  Do you think that I wrote that code for no good
> reason?  The kernel was being nice and telling you what you did wrong,
> don't try to fake it out, it's smarter than you are here.
> 
> I also get to tell you that you need to fix this up right now, BEFORE
> 3.4 comes out.
> 
> And no, just because you created static struct devices, this is not ok,
> DO NOT create static struct devices, that's foolish, and even worse, not
> something you should be doing in the first place, create a real
> structure, and put a struct device within it please.

That was not really  my intention here.
But it is my fault for not keeping up with the documentation. For what
is worth, back on the days that the framework was initially written,
there was no such documentation and I went for a simple API approach
(alloc -> register -> unregister -> free). It also made quite trivial
the hsi_port allocation/freeing and device registration.

I'll do the changes asap.

> 
> And people wonder why kernel maintainers are grumpy.
> 
> > +/**
> > + * struct hsi_client - HSI client attached to an HSI port
> > + * @device: Driver model representation of the device
> > + * @tx_cfg: HSI TX configuration
> > + * @rx_cfg: HSI RX configuration
> > + * @hsi_start_rx: Called after incoming wake line goes high
> > + * @hsi_stop_rx: Called after incoming wake line goes low
> > + */
> > +struct hsi_client {
> > +	struct device		device;
> > +	struct hsi_config	tx_cfg;
> > +	struct hsi_config	rx_cfg;
> > +	void			(*hsi_start_rx)(struct hsi_client *cl);
> > +	void			(*hsi_stop_rx)(struct hsi_client *cl);
> > +	/* private: */
> > +	unsigned int		pclaimed:1;
> > +	struct list_head	link;
> > +};
> 
> Why do you need another list_head in here?  What's wrong with using the
> device iteration functions that are written for you to use?  Don't put
> the structure on yet-another-list, use what is given to you please, as
> odds are, you will traverse this list incorrectly (trust me...)
> 

Well I do agree about using the device iteration functions, and way back
in the old times of this framework that was the case:

https://lkml.org/lkml/2010/5/7/240

The issue here was that I wanted to allow the hsi_controllers drivers to
call hsi_event() in their BHs and ISR to minimize the latency in the
communication . And that's not possible if I use the
device_for_each_child() in hsi_event(), cause the locking does not
protect against interrupt handlers. 

But I guess I can go back to the old code and push the issue down to the
the hsi controller drivers and force them to use threaded interrupts...

> ugh,
> 
> greg k-h

Br,
Carlos Chinea