linux-kernel - Re: [PATCH 01/16] gpio: dwapb: Use modern PM macros

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Message-ID: <20250820191039.4f8af41e@barney>
Date: Wed, 20 Aug 2025 19:10:39 +0200
From: Michael Büsch <mb@...s.ch>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Jisheng Zhang <jszhang@...nel.org>, Doug Berger <opendmb@...il.com>,
 Florian Fainelli <florian.fainelli@...adcom.com>, Linus Walleij
 <linus.walleij@...aro.org>, Bartosz Golaszewski <brgl@...ev.pl>, Michael
 Buesch <m@...s.ch>, Hoan Tran <hoan@...amperecomputing.com>, Andy
 Shevchenko <andy@...nel.org>, Daniel Palmer <daniel@...ngy.jp>, Romain
 Perier <romain.perier@...il.com>, Grygorii Strashko
 <grygorii.strashko@...com>, Santosh Shilimkar <ssantosh@...nel.org>, Kevin
 Hilman <khilman@...nel.org>, Robert Jarzmik <robert.jarzmik@...e.fr>,
 Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>, Masami Hiramatsu
 <mhiramat@...nel.org>, Shubhrajyoti Datta <shubhrajyoti.datta@....com>,
 Srinivas Neeli <srinivas.neeli@....com>, Michal Simek
 <michal.simek@....com>, Broadcom internal kernel review list
 <bcm-kernel-feedback-list@...adcom.com>, linux-gpio@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-omap@...r.kernel.org, linux@...tq-group.com
Subject: Re: [PATCH 01/16] gpio: dwapb: Use modern PM macros

On Wed, 20 Aug 2025 19:54:44 +0300
Andy Shevchenko <andy.shevchenko@...il.com> wrote:

> > The dwapb_context structure is always embedded into struct
> > dwapb_gpio_port to simplify code. Sure this brings a tiny 36 bytes
> > data overhead for !CONFIG_PM_SLEP.  
> 
> I don't think it's a good approach to add a lot of data for peanuts in
> case of PM_SLEEP=n.

It wastes 36 bytes in case of PM=n.

The driver currently allocates the struct with kzalloc and stores a pointer to it
in case of PM=y.
So this probably has an overhead in the same order of magnitude (pointer +
malloc overhead/alignment/fragmentation) in case of PM=y now.

-- 
Michael Büsch
https://bues.ch/

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