linux-kernel - Re: [PATCH v4 0/3] serial: sc16is7xx: cosmetic cleanup

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Message-ID: <76e5feba-1107-47af-af3c-57a7cb6b601c@camlingroup.com>
Date: Wed, 4 Sep 2024 16:18:41 +0200
From: Lech Perczak <lech.perczak@...lingroup.com>
To: Jiri Slaby <jirislaby@...nel.org>, linux-serial@...r.kernel.org
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Hugo Villeneuve <hvilleneuve@...onoff.com>,
 Krzysztof Drobiński <k.drobinski@...lintechnologies.com>,
 Pawel Lenkow <p.lenkow@...lintechnologies.com>,
 Kirill Yatsenko <kirill.yatsenko@...lingroup.com>,
 Andy Shevchenko <andy@...nel.org>
Subject: Re: [PATCH v4 0/3] serial: sc16is7xx: cosmetic cleanup

Hello Jiri,

W dniu 28.08.2024 o 06:35, Jiri Slaby pisze:
> On 27. 08. 24, 17:38, Lech Perczak wrote:
>> Only the single expansion of GENMASK proves very hard to analyze in the
>> diff - so I double-checked with a calculator,
>> though all BIT() expansions do match, as does the updated definition.
>> of SC16IS7XX_LSR_BRK_ERROR_MASK.
> 
> You can diff also the generated .o fed through objdump -d (generated .s 
> usually contains line numbers).

I see that Greg already got the series into tty-next, but for the sake of completeness,
I did the check anyway.
This also came to my mind after I posted diff of preprocessed source ;-)

The diff is way, way smaller, but functionality is the same.
On amd64, the sign extension used in BIT() is visible:

--- sc16is7xx.c.asm.1	2024-09-04 16:06:02.523038659 +0200
+++ sc16is7xx.c.asm.2	2024-09-04 16:05:42.103938886 +0200
@@ -289,17 +289,16 @@
      1f9:	c7 44 24 04 00 00 00 	movl   $0x0,0x4(%rsp)
      200:	00 
      201:	e8 00 00 00 00       	call   206 <sc16is7xx_tx_empty+0x36>
-     206:	8b 44 24 04          	mov    0x4(%rsp),%eax
-     20a:	c1 e8 06             	shr    $0x6,%eax
-     20d:	83 e0 01             	and    $0x1,%eax
-     210:	48 8b 54 24 08       	mov    0x8(%rsp),%rdx
-     215:	65 48 2b 14 25 28 00 	sub    %gs:0x28,%rdx
-     21c:	00 00 
-     21e:	75 09                	jne    229 <sc16is7xx_tx_empty+0x59>
-     220:	48 83 c4 10          	add    $0x10,%rsp
-     224:	e9 00 00 00 00       	jmp    229 <sc16is7xx_tx_empty+0x59>
-     229:	e8 00 00 00 00       	call   22e <sc16is7xx_tx_empty+0x5e>
-     22e:	66 90                	xchg   %ax,%ax
+     206:	0f b6 44 24 04       	movzbl 0x4(%rsp),%eax
+     20b:	48 c1 e8 06          	shr    $0x6,%rax
+     20f:	83 e0 01             	and    $0x1,%eax
+     212:	48 8b 54 24 08       	mov    0x8(%rsp),%rdx
+     217:	65 48 2b 14 25 28 00 	sub    %gs:0x28,%rdx
+     21e:	00 00 
+     220:	75 09                	jne    22b <sc16is7xx_tx_empty+0x5b>
+     222:	48 83 c4 10          	add    $0x10,%rsp
+     226:	e9 00 00 00 00       	jmp    22b <sc16is7xx_tx_empty+0x5b>
+     22b:	e8 00 00 00 00       	call   230 <sc16is7xx_tx_empty+0x60>
      230:	90                   	nop
      231:	90                   	nop
      232:	90                   	nop

> 
> regards,

-- 
Pozdrawiam/With kind regards,
Lech Perczak

Sr. Software Engineer
Camlin Technologies Poland Limited Sp. z o.o.