linux-kernel - Re: [PATCH] serial: 8250

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Message-ID: <f84c2ee3-77b4-41c4-8517-26dfb44a2276@kernel.org>
Date: Fri, 11 Jul 2025 07:03:56 +0200
From: Jiri Slaby <jirislaby@...nel.org>
To: Chaitanya Vadrevu <chaitanya.vadrevu@...rson.com>,
 gregkh@...uxfoundation.org
Cc: linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
 kernel test robot <lkp@...el.com>, Jason Smith <jason.smith@...rson.com>,
 Gratian Crisan <gratian.crisan@...rson.com>
Subject: Re: [PATCH] serial: 8250_ni: Fix build warning

On 11. 07. 25, 0:38, Chaitanya Vadrevu wrote:
> Allocate memory on heap instead of stack to fix following warning that
> clang version 20.1.2 produces on W=1 build.
> 
> drivers/tty/serial/8250/8250_ni.c:277:12: warning: stack frame size (1072) exceeds limit (1024) in 'ni16550_probe' [-Wframe-larger-than]

Hmm, OK:
$ pahole -sy uart_8250_port drivers/tty/serial/8250/8250_port.o
uart_8250_port  784     4

That's quite a few. I am not sure why we did not see this earlier? 
Perhaps because CONFIG_FRAME_WARN is set higher for most use/compilation 
cases.

Should we switch all probes?

I have a patchset to move ops to a separate struct (pointer), but that's 
far from finished and it does not save that much:
uart_8250_port  624     4

Another question is if we can introduce some lightweight struct for 
register instead of full uart_8250_port which is copied from (and only 
small part of it).

So perhaps:
Reviewed-by: Jiri Slaby <jirislaby@...nel.org>

thanks,
-- 
js
suse labs