Re: [PATCH v7 03/14] ASoC: Intel: catpt: Add IPC message handlers

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Mon, Sep 21, 2020 at 05:20:12PM +0300, Andy Shevchenko wrote:
> On Mon, Sep 21, 2020 at 03:58:33PM +0200, Amadeusz Sławiński wrote:
> > On 9/21/2020 2:59 PM, Andy Shevchenko wrote:
> > > > +struct catpt_set_volume_input {
> > > > +	u32 channel;
> > > > +	u32 target_volume;
> > > > +	u64 curve_duration;
> > > > +	enum catpt_audio_curve_type curve_type __aligned(4);
> > > > +} __packed;
> > > How this __packed changes anything? In general __packed doesn't make sense for
> > > in-kernel data structures. Otherwise you have to use proper (POD) types for
> > > data. Ditto for all similar cases.
> > 
> > All of __packed use in code is done on structures used to communicate with
> > FW, which is binary interface, so it is not kernel only structure, as it is
> > also FW one. While we can expect compiler to do the right thing, I consider
> > it is better to be explicit about what kind of data we are handling, so
> > there aren't any surprises.
> 
> Size of enum is compiler defined. It may not be used in the ABIs.

I have to elaborate that I'm talking in ABIs which implies different compilers
and even may be run on different CPU architectures.

> __uXX vs. uXX I dunno.

And here I'm talking about FW <--> OS interface. It's not user visible ABI, but
still some Ext <--> Int protocol. I saw uXX types in data structures of FW
communication protocols.

-- 
With Best Regards,
Andy Shevchenko