linux-kernel - Re: [PATCH v2 22/28] Input/joystick/analog: Convert from seq

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Date:   Thu, 19 May 2022 16:19:27 -0400
From:   Kent Overstreet <kent.overstreet@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...r.kernel.org,
        pmladek@...e.com, rostedt@...dmis.org, senozhatsky@...omium.org,
        willy@...radead.org
Subject: Re: [PATCH v2 22/28] Input/joystick/analog: Convert from seq_buf ->
 printbuf

On Thu, May 19, 2022 at 11:04:27PM +0300, Andy Shevchenko wrote:
> On Thu, May 19, 2022 at 01:24:15PM -0400, Kent Overstreet wrote:
> > seq_buf is being deprecated, this converts to printbuf which is similar
> > but heap allocates the string buffer.
> > 
> > This means we have to consider memory allocation context & failure: Here
> > we're in device initialization so GFP_KERNEL should be fine, and also as
> > we're in device initialization returning -ENOMEM is fine.
> 
> ...
> 
> > +       int ret = 0;
> 
> Redundant assignment.
> 
> ...
> 
> > -		seq_buf_printf(&s, " %d-hat",
> > -			       hweight16(analog->mask & ANALOG_HATS_ALL));
> > +		pr_buf(&buf, " %d-hat",
> > +		       hweight16(analog->mask & ANALOG_HATS_ALL));
> 
> Now you may put it on one line here and in similar cases.
> 
> ...
> 
> > +	ret = buf.allocation_failure ? -ENOMEM : 0;
> > +	if (!ret)
> > +		strlcpy(analog->name, buf.buf, sizeof(analog->name));
> > +	printbuf_exit(&buf);
> > +	return ret;
> 
> Looks like anti-pattern. On top a bit twisted error code manipulation before
> checking for error codes, but what about

This conversion predated my adding external buffers to printbufs - now the patch
is more of a direct conversion:

-- >8 --
Subject: [PATCH] Input/joystick/analog: Convert from seq_buf -> printbuf

seq_buf is being deprecated, this converts to printbuf.

Signed-off-by: Kent Overstreet <kent.overstreet@...il.com>
---
 drivers/input/joystick/analog.c | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/drivers/input/joystick/analog.c b/drivers/input/joystick/analog.c
index 3088c5b829..1dde969b29 100644
--- a/drivers/input/joystick/analog.c
+++ b/drivers/input/joystick/analog.c
@@ -19,7 +19,7 @@
 #include <linux/input.h>
 #include <linux/gameport.h>
 #include <linux/jiffies.h>
-#include <linux/seq_buf.h>
+#include <linux/printbuf.h>
 #include <linux/timex.h>
 #include <linux/timekeeping.h>
 
@@ -339,24 +339,21 @@ static void analog_calibrate_timer(struct analog_port *port)
 
 static void analog_name(struct analog *analog)
 {
-	struct seq_buf s;
+	struct printbuf buf = PRINTBUF_EXTERN(analog->name, sizeof(analog->name));
 
-	seq_buf_init(&s, analog->name, sizeof(analog->name));
-	seq_buf_printf(&s, "Analog %d-axis %d-button",
-		 hweight8(analog->mask & ANALOG_AXES_STD),
-		 hweight8(analog->mask & ANALOG_BTNS_STD) + !!(analog->mask & ANALOG_BTNS_CHF) * 2 +
-		 hweight16(analog->mask & ANALOG_BTNS_GAMEPAD) + !!(analog->mask & ANALOG_HBTN_CHF) * 4);
+	pr_buf(&buf, "Analog %d-axis %d-button",
+	       hweight8(analog->mask & ANALOG_AXES_STD),
+	       hweight8(analog->mask & ANALOG_BTNS_STD) + !!(analog->mask & ANALOG_BTNS_CHF) * 2 +
+	       hweight16(analog->mask & ANALOG_BTNS_GAMEPAD) + !!(analog->mask & ANALOG_HBTN_CHF) * 4);
 
 	if (analog->mask & ANALOG_HATS_ALL)
-		seq_buf_printf(&s, " %d-hat",
-			       hweight16(analog->mask & ANALOG_HATS_ALL));
-
+		pr_buf(&buf, " %d-hat", hweight16(analog->mask & ANALOG_HATS_ALL));
 	if (analog->mask & ANALOG_HAT_FCS)
-		seq_buf_printf(&s, " FCS");
+		pr_buf(&buf, " FCS");
 	if (analog->mask & ANALOG_ANY_CHF)
-		seq_buf_printf(&s, (analog->mask & ANALOG_SAITEK) ? " Saitek" : " CHF");
+		pr_buf(&buf, (analog->mask & ANALOG_SAITEK) ? " Saitek" : " CHF");
 
-	seq_buf_printf(&s, (analog->mask & ANALOG_GAMEPAD) ? " gamepad" : " joystick");
+	pr_buf(&buf, (analog->mask & ANALOG_GAMEPAD) ? " gamepad" : " joystick");
 }
 
 /*
-- 
2.36.0