linux-kernel - Re: [PATCH] fbtft: reduce stack usage

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Message-ID: <aEgOpxYVSROvbpl_@smile.fi.intel.com>
Date: Tue, 10 Jun 2025 13:53:27 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Arnd Bergmann <arnd@...db.de>
Cc: Arnd Bergmann <arnd@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Riyan Dhiman <riyandhiman14@...il.com>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Paolo Perego <pperego@...e.de>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Matthew Wilcox <willy@...radead.org>,
	Jeff Johnson <jeff.johnson@....qualcomm.com>,
	dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
	linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fbtft: reduce stack usage

On Tue, Jun 10, 2025 at 12:35:14PM +0200, Arnd Bergmann wrote:
> On Tue, Jun 10, 2025, at 12:26, Andy Shevchenko wrote:
> > On Tue, Jun 10, 2025 at 11:24:38AM +0200, Arnd Bergmann wrote:

...

> >> +static noinline_for_stack void fbtft_write_register_64(struct fbtft_par *par,
> >> +							int i, int buf[64])
> >
> > Perhaps int i, int buf[64] should be u32?
> 
> Right, I can send an updated patch, or this could be fixed up when applying
> the patch

Greg doesn't do that (or won't do anyway), so either a followup or a v2.

...

> > Wondering if we may reuse this in other cases (by providing the additional
> > length parameter). But it may be done later on.
> 
> I tried this and that quickly became a mess. It is probably a good
> idea to rework the code to completely avoid the varargs function
> pointer and instead take an array here, but this is not something
> I could easily do myself as that takes more time and needs better
> testing.

Right and this driver in any case in a frozen position, so it might never
happen, though.

-- 
With Best Regards,
Andy Shevchenko