linux-kernel - Re: [PATCH v1 3/3] spi: xilinx: Make num_chipselect 8-bit in the struct xspi_platform

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Date: Fri, 8 Mar 2024 17:01:19 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Michal Simek <michal.simek@....com>
Cc: linux-spi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH v1 3/3] spi: xilinx: Make num_chipselect 8-bit in the
 struct xspi_platform_data

On Fri, Mar 08, 2024 at 03:00:55PM +0100, Michal Simek wrote:
> On 3/8/24 14:55, Andy Shevchenko wrote:
> > On Fri, Mar 08, 2024 at 02:48:04PM +0100, Michal Simek wrote:
> > > On 3/8/24 14:31, Andy Shevchenko wrote:
> > > > On Fri, Mar 08, 2024 at 09:20:23AM +0100, Michal Simek wrote:
> > > > > On 3/7/24 16:43, Andy Shevchenko wrote:

..

> > > > > >     struct xspi_platform_data {
> > > > > > -	u16 num_chipselect;
> > > > > > -	u8 bits_per_word;
> > > > > > -	struct spi_board_info *devices;
> > > > > > -	u8 num_devices;
> > > > > >     	bool force_irq;
> > > > > > +	u8 num_chipselect;
> > > > > > +	u8 bits_per_word;
> > > > > > +	u8 num_devices;
> > > > > 
> > > > > all above have 32bits. It means on 64bit cpu you have 32bit gap here.
> > > > 
> > > > > > +	struct spi_board_info *devices;
> > > > 
> > > > On all architectures? I mean do all 64-bit architecture ABIs _require_
> > > > the pointer to be aligned at 8-byte boundary? Even if so, the struct
> > > > itself can be aligned on 4-byte boundary.
> > > 
> > > I am not able to tell if toolchain enforce 8byte alignment by default/by
> > > setup on all 64bit systems.
> > > I am using pahole to check this which was recommended by Greg in past which
> > > reports gap in the middle.
> > 
> > I see, thanks for explanation.
> > 
> > Yes, it's likely that in some cases it will be a gap on 64-bit platforms, but
> > after this patch no gap on 32-bit. Do you still want me to reshuffle that as
> > you suggested?
> 
> Yes I would prefer to do that change when you are doing cleanup.

Can you give your tag? Then I prepare a new version with addressed comments
against last patch.

-- 
With Best Regards,
Andy Shevchenko